SECTIONEDITOR

of the Committee on Scientific Investigation merican Academy of Restorative Dentistry Malcolm Stephen Judson

D. Jendresen, DDS, PhD,a Edward P. Allen, DDS, C. Bayne, MS, PhD, Tore L. Hansson, DDS, Odont Klooster, DDS, and Jack D. Preston, DDS

San Francisco,

of th

PhD, Dr,

Calif.

The committee screened several hundred articles, citing 518 published papers. Some are present quality in research, others provide clinical interest, and some are identified as misleading. New techniques in pulp physiology and pathology are reported. Laser use and techniques in prevention, restorative dentistry, and materials use are reported. Epidemiology of selected diseases and the results of various formulations for treatment are cited. Diagnosis of craniomandibular dysfunction is well represented as well as references to literature reviews and other sophisticated scientific investigation. Research on adhesives is presented in respect to bonding agents for dentin and enamel. Several clinical studies are included, along with customary laboratory reports on several materials. (J PROSTHET DENT 1992;68:137-190.) AS THE VISTAS OF RESEARCH extend forward and the skills and technology involved in scientific investigation become more and more elegant, the task of keeping abreast of the increasing volume of literature is becoming one of heroic proportions. The mere problem of communication among scientists, with 100,000 scientific journals and 1,850,OOO articles now appearing annually, is of such magnitude that little time is provided for the more important responsibility of evaluating this literature and then synthesizing the useful information into a constructive and definitive investigation program. Perhaps paramount among the problems growing out of the current volume of investigation is the challenge of maintaining and improving the quality of research. As Fortune says (and my apologies for expressive terminology): “We research the hell out of everything. We contemplate very little.” Lord Chesterton bas remarked: “A great deal of research is like a blind man in a dark room looking for a black hat that isn’t there.” Thus, the charge to this committee of reviewing the literature and, more important, presenting to you an accurate profile of the new knowledge that is truly meaningful becomes increasingly formidable each year. I believe I speak for your committee when

he previous

paragraphs

are

the

words

from

the

Report

of the Committee on Scientific Investigation presented 30 years ago at this meeting by Doctor Ralph W. Phillips. If I had written an original introduction to this

Presented at the American Academy meeting, Chicago, Ill. aCommittee Chairman. Other authors tee members. IO/l/37897

THE

JOURNAL

OFPROSTHETIC

of Restorative of this article

DENTISTRY

Dentistry are Commit-

I suggest that in the future more serious thought may have to be given to the feasibility of limiting this report each year to specific areas of interest and reporting the progress in these selected fields in greater depth. Thus, the total subject matter might be evaluated over a two-year period, rather than annually. In this manner, the review could be more definitive and decidedly more documentary. Thus, as I stated last year, I preface this review by requesting your indulgence in acknowledging that no committee could encompass all of the investigations that rightfully constitute the expanding parameters of dental research. Attention in this report will be focused on those areas that would seem to be most closely related to the interests of this group and to the investigations which would appear to have the greatest influence on the future theory and practice of restorative dentistry. A sincere attempt has been made this year to compile this report as a critical eualuation of the literature rather than as a simple citation of the published literature. It is my hope then that the following analysis is a correct interpretation of helpful information submitted by the members of this c0mmittee.l

year’s report, it would have embraced essentially the same principles that Ralph Phillips has underlined over these years; the same information, the same concerns, and the same approach to evaluating the literature. This is illustrative of the tone and standards set by Dr. Phillips three decades ago to help this committee establish and maintain a quality report. He was a member of this committee since 1960 and was its chairman for 14 of those years. Ralph Phillips’ death this year is not just a personal loss to those who knew him but an irreparable loss to the dental profession itself.

137

JENDRESEN

This year the committee members screened several hundred articles and cited 518 references in this report. Some are cited because of their outstanding quality and contribution, others because they are of continuing clinical interest despite being repetitive, and yet others just because they were thought to be misleading or poorly done.

PULP

BIOLOGY

The newer study techniques employed to expand the understanding of pulp physiology and pathology may provide a dynamic rather than a static perspective. Much of the investigative effort reported during the past year focused on analyzing inflammatory response at the cellular level. Historically, the body of knowledge regarding the cellular components of the dental pulp has been derived primarily from classic methods of histology, biochemistry, and immunology. The importance of the studies cited in this section focuses more on the usefulness of these study techniques to reach a better understanding of pulp biology, instead of on the specific study results reported by each investigator. Mangkornkarn et a1.2 reported a method to analyze vital human pulp tissue by flow cytometry. In this method, two analyses of the prepared pulpal tissue were done. First, the prepared tissue was stained with monoclonal antibodies to detect lymphocyte subpopulations. Second, the tissue was processed for DNA analysis of individual cells. The results reported in this study demonstrate the feasibility of using flow cytometric analysis to examine at a quantitative level the cellular heterogeneity of the human dental pulp. Rauschenberger, et a1.3 noted that “lysosomal granules of polymorphonuclear leukocytes (PMNs) contain proteolytic enzymes and other components important in the regulation of inflammation and the elimination of bacteria or debris associated with pulp disease.” Since it is known that PMN lysosomal degranulation is nonspecific and can result in destruction of healthy connective tissue adjacent to the area of damaged or infected tissue, the authors used a modified enzyme-linked immunoadsorbent assay to detect the human PMN lysosomal granule products: elastase, cathepsin @, and lactoferrin. The authors demonstrated that a modified enzyme-linked irnmunoadsorbent assay technique can be used to measure PMN lysosomal granule components in the dental pulp tissue. They also concluded that “elastase and lactoferrin levels appear to be valid diagnostic markers of advanced pulpal disease.” Davis et a1.4 sought information concerning the presence of a free radical scavenging (inactivating, dismutating) enzyme, superoxide dismutase, in hu:man dental pulp. They noted that these free radicals (such as the superoxide anion radical (0~~) and the hydroxyl anion radical (OH. ), are powerful biologic oxidants produced by phagocytes during normal tissue response to injury and infection. They assayed both normal and inflamed dental pulps for the presence of superoxide dismutase and reported that this enzyme was identified in the normal pulp tissues. These 138

ET AL

investigators were able to make comparative measures of the activity levels of this enzyme in normal pulp tissues and those showing inflammatory response. They concluded that the human dental pulp has an endogenous defense mechanism designed to protect the tissue components (cells and matrix) from the toxic effects of the reactive oxygen intermediates. Jacoby et a1.j used immunohistochemical techniques and routine transmission electron microscopy to identify the presence of von Willebrand factor (vWF), a blood-clotting factor essential to normal hemostasis, and the WiebelPalade bodies (WPBs) in the endothelial cells lining the blood vessels from both normal and inflamed human pulpal tissues. Morphometric analyses conducted on these tissues with either light or transmission electron microscopy showed that significantly more vWF-positive blood vessels were seen in the inflamed tissues. Supporting these findings, transmission electron microscopy showed that more vascular endothelial cells contained WPBs in the inflamed tissues when compared with the normal tissues. From these observations, the authors concluded that it “appears that during pulpal inflammation, the cascade of events associated with hemostasis may be activated with the increased synthesis and release of vWF by endothelial cells.” McClanahan et a1.6 used enzyme-linked immunoadsorbent assay techniques to compare histological examination of normal samples (collected from nondiseased third-molar teeth planned for extraction) with inflamed human pulps collected from teeth with deep carious lesions. The focus of this study was on the role of proteinase inhibitors oiz-antitrypsin and az-macroglobulin. They concluded that “these two protease inhibitors in the human dental pulp tissue and the increase in the concentration of acute inflammation indicates that these proteins play a role in the pathogenesis of pulpal inflammatory disease.” The results of the study are not remarkable, but the study methodology holds promise for a broader understanding of the histopathology of pulpal inflammatory disease. Carbon dioxide (COz) laser techniques have been receiving increased attention for use in preventive and restorative dentistry (for the sealing of pits and fissures, by fusion of biomaterials to enamel, treatment of carious lesions, inhibition of enamel and dentin, demineralization, etching of enamel, and preparation of retention pin holes); this interest accentuates the importance of a study technique to evaluate the heat effects of CO2 irradiation on the dental

PUlP. Friedman et a1.7 studied the effect of CO2 laser irradiation on pulpal microcirculation in cat canines. The enamel surfaces of four teeth were exposed with energy specified densities, by use of either a handpiece or a microslad, with a focal spot of 0.21 mm and 0.33 mm respectively. Pulpal blood flow (PBF) before and after lasing was recorded through the intact tooth surfaces by a laser Doppler flow meter. Carbon dioxide laser irradiation caused an increase in PBF, which was immediate and transient. The increase JULY

1992

VOLUME

68

NUMBER

1

COMMITTEE

REPORT

was higher in a large pulp than in a small pulp, and it was inversely related to the focal spot size. These findings confirm that the dental pulp is thermally affected by COs lasing of the tooth surface, but under appropriate control this may occur without extensive pulp coagulation. The most important observation from this study is that the effects of laser irradiation on the pulpal microcirculation may be studied in situ by means of the method presented. Restorative dentists have a degree of general agreement on the importance of finishing techniques used in optimal restorative dentistry. These finishing strategies provide for improved metallurgic properties, better marginal adaptations, and reduced plaque accumulation. There has been a traditional concern about the frictional abrasion produced in the finishing process and many studies focus their concern on heat rise, which has been labeled “the most serious single insult to the p~lp.“~ In a recent in vitro study, Stewart et a1.g undertook to evaluate the effect of four variables on the temperature rise produced by the finishing of restorations. These variables were (1) restorative material, (2) finishing agent, (3) finishing time, and (4) depth of dentin under the restoration. Class V preparations were cut on extracted premolars and restored with amalgam, composite, or glass ionomer cement. Finish was accomplished with wet pumice and cup, wet pumice and a brush, a grit rubber polishing point, and an aluminum oxide-coated disc. Finishing time was continuous or intermittent for up to 1 minute; dentin under the restoration was 0.5 mm to 3.0 mm. The authors reported that “amalgam produced the highest temperature rises at the pulp, while composite and glass ionomer were no different than the untreated (virgin) tooth. Aluminum oxide discs produced the largest temperature rise, wet pumice with a brush the least.” They also noted that temperature rise increased “almost linearly with continuous finishing, while intermittent finishing significantly reduced temperature rise in all cases.” Until a noninvasive method can be devised to reliably measure heat rise in vivo, the clinician must use interpretive extrapolation of these in vitro observations in each clinical situation. A related traditional concern of restorative dentists is the effect of drying techniques commonly used in cavity preparation and maintenance during restorative procedures, on the response of the dental pulp. Galan et al.,iO used recently extracted human maxillary central incisors and cuspids mounted in polymethyl methacrylate so that the root portions were embedded up to the cementoenamel junction. This study was designed to determine the effects different warm air-drying conditions have on intrapulpal temperature, with or without chamfer preparations and with or without an acid-etching treatment of the enamel. Lingual access openings were prepared in each of these incisor and canine teeth to accommodate a thermal sensor probe. Half of the specimens received a labial chamfer preparation and half were acid-etched. In this laboratory study, the authors concluded that exposure to warm-air drying increased the intrapulpal temperature and could be detrimental to pulTHE

JOURNAL

OF PROSTHETIC

DENTISTRY

pal health. They recommended that exposure time to drying devices be kept short (less than 15 seconds) and applied at a distance greater than 6 cm from the tooth. This study provided an interesting method to measure the heat rise that dentists often surmise; however, the focus of concern was limited to heat rise and possible thermal-induced damage. A weakness in this study was that no effort was made to measure the extent of the desiccating effect, with its potential for destruction of cellular processes in the dentinal tubules. In another study, three intermediary base materials, a zinc oxide-eugenol (Cavitec, Kerr USA, Romulus, Mich.) and two calcium hydroxide liners (Life, Kerr USA, and Dycal, Caulk, Milford, Del.), were selected at random for use as base materials beneath amalgam or composite resin restorations on humans after complete carious removali Life and Dycal liners, selected at random, were also used as direct and indirect capping agents as clinically indicated. Clinical evaluations of signs and symptoms were made before treatment and at l-week, 6-month and l-year intervals after treatment. Histologic evaluations were performed on three complete caries-removal teeth and 18 direct pulpcapping teeth 6 months after treatment. The authors reported that “no significant differences in clinical symptomatology resulted between the materials in the complete caries removal group or the indirect and direct pulp capping groups.” In the histologic evaluation, all the control teeth, irrespective of the presence or absence of clinical caries, had normal cellular morphology with no inflammation present. The authors reported normal cellular morphology and no inflammatory reaction in any of the three complete caries-removal teeth. There were no significant differences in histologic response to the calcium hydroxide intermediary bases Life and Dycal, in direct pulpcapping teeth after 6 months of treatment. Teeth treated with Life and Dycal liners had dentin bridges that consisted of tubular dentin, amorphous dentin, amorphous debris, cellular inclusions, and dentin chips in varying amounts and combinations. The authors also presented an interesting chart of “criteria for grading tooth pulp histology.”

PREVENTIVE

DENTISTRY

From more than 200 citations on preventive dentistry, a small number of studies were selected as examples of current thinking and practice in preventive dentistry and the research efforts relating to this theme.

Oral hygiene Toothbrushing with a dentifrice has been an accepted means of tooth cleaning for most of the current century. Rinses have also been used as vehicles for delivering oral therapeutic ingredients, such as fluoride and antiplaque agents. Noting that oral rinsing habits were found to influence dental caries, Duckworth et a1.12 designed an oral fluoride clearance study to test a possible mechanism for the observed effects. Their findings indicate that rinsing hab139

JENDRESEN

ET AL

its “may play an important role in the oral retention of fluoride from dentifrices which may, in turn, affect their clinical efficacy.” Commonly, gingivitis is an early precursor to periodontitis; thus controlling the severity of gingivitis is an important factor in preventing periodontitis. In various degrees, gingivitis can be controlled by the use of mechanical cleaning devices that disrupt or remove bacterial plaque and by using chemical agents that retard plaque formation. Finkelstein et a1.13 developed a study to compare the effectiveness of these categoric therapeutic modalities. Specifically, the clinical study was undertaken “to compare the effectiveness of two interdental mechanical oral hygiene devices and two antimicrobial mouth rinses in reducing pla.que and gingivitis levels over a three-month period.” Subjects were randomly assigned to one of five test groups that would use either a wooden interdental cleaner (Stim-U-Dent, Johnson & Johnson, New Brunswick, N.J.) or a waxed dental floss (Johnson & Johnson), an essential oil mouth rinse (Listerine Antiseptic, Warner-Lambert Co., Norris Plains, N.J.), a cetyl pyridinium chloride (CPC) mouth rinse (Cepacol, Merrell Dow Pharmaceuticals Inc., Cincinnati, Ohio). Toothbrushing alone served as a control. As might be expected, the results of this study suggest that antimicrobial rinses reduce plaque on visible tooth surfaces but do not penetrate sufficiently between the teeth to affect interdental plaque and thus interdental inflammation. The authors comment that “by disturbing interdental plaque, both dental floss and the interdental cleaner have little effect on visible tooth surface plaque accumulation, yet produce a significant reduction in gingival inflammation.”

whether such changes were measurable. Cohorts of children aged 7 to 12 years, born before or after the fluoride reduction, were examined clinically according to Dean’s fluorosis index. The authors concluded that the study confirms preliminary findings that variation in dental fluorosis arising from minor changes to the fluoride level in drinking water is measurable. It would be useful to apply the techniques of this study in other regions where concern over dental fluorosis has resulted in changes in the levels of fluoride concentration.

Fluorides

Plaque

Recent animal studies focused public attention on the potential carcinogenicity of fluoride; this, in turn, prompted an examination of bone cancer incidence rates. Mahoney et all4 studied trends in the incidence of primary bone cancers (including osteosarcomas) among residents of New York State, exclusive of New York City. The New York State Cancer Registry has been operational since 1970, providing a 20-year data base. The average annual osteosarcoma incidence rates in fluoridated and nonfluoridated areas were compared; these incidence rates were compared for regions in New York State before and after water fluoridation was introduced. After examination of these data, the authors concluded that the data “do not support an association between fluoride in drinking water and the occurrence of cancer of the bone.” Concern over possible adverse health consequences of water fluoridation, including dental fluorosis appears to be a factor that may influence consideration of water fluoridation by some communities. Partly because of this concern, the drinking water fluoride concentration in Hong Kong was reduced by 0.2 ppm in June 1978. A study was made by Evans and Stamm lj to determine whether this reduction had produced a decrease in dental fluorosis and

Park et a1.i7 emphasized the usefulness of biotelemetry as a means of directing continuous monitoring of biological phenomena without disturbing the physiologic and microbiological processes being evaluated. This study was designed to observe plaque pH responses following the ingestion of meals purchased from a fast-food restaurant and the effect of chewing sorbitol gum on those plaque pH responses, as measured by an indwelling interproximal glass pH electrode wire-telemetry system. In a pilot study with 12 fast-food meals, the most acidogenic breakfast, lunch, and dinner were selected for this study. Five adult panelists participated; the fasted, resting plaque pH was recorded for 5 minutes, the panelists ingested the selected meals for 10 minutes, and rinsed thoroughly with 50 mm of tap water. The pH response was then monitored for the remainder of a 2-hour period. In a second test series the same procedures were followed through the post meal ingestion rinse. After the pH response to the meal was monitored for 5 minutes, the panelists chewed a sorbitol gum for 15 minutes. Panelists ate the test foods with and without the chewing gum according to a randomized-block test design. The investigators concluded that the “use of sorbitol gum significantly raised the plaque pH, prevented the

140

Sealants Although nearly 70% of dentists in the United States report regular sealant use, Gerlach and Senningr6 observed that “increased professional acceptance has apparently not resulted in optimal access to care, since cross-sectional surveys report that only 6-8 percent of children in the United States have sealants.” Recognizing the possible need for management of sealant use in public or private dental insurance programs, the authors assessed the use of sealants in one insured population in Vermont, with reference to the appropriateness of the criteria for managing provider behavior regarding both treatment and eligibility. They recommend including sealant coverage as part of publicly funded dental programs and note that such programs “may not require excessive management to control utilization, since provider behavior is typically consistent with professional treatment guidelines, and overall utilization is likely to be low. Practices that encourage usage, such as unrestricted coverage of sealants as a routine insurance benefit for children may be preferred.”

inhibition

and control

JULY

1992

VOLUME

68

NUMBER

1

COMMITTEE

REPORT

subsequent pH drops after the fast-food meal ingestion and reduced the pH curve area under 5.5.” The similarity of these results by several investigators emphasized the usefulness of the telemetry study technique and affirmed that oral clearance rates are enhanced by the use of sorbitol gum during the period immediately following food ingestion. Antimicrobial agents have been proposed as playing an important role in controlling plaque and gingivitis. Marshis suggests that a large number of potential compounds are unsuitable for use in dentifrices because they lack “substantivity,” produce undesirable side effects, or are incompatible with toothpaste ingredients. Agents that have been successfully incorporated into dentifrices include plant extracts, phenolic compounds, and methyl salts. Some currently used products are based on the phenol, triclosan. Triclosan is reported to have a broad spectrum of antimicrobial activity against yeasts and oral bacteria. In the effort to augment its clinical efficacy, triclosan has been combined. with either a copolymer or another compatible antimicrobial agent, zinc citrate. In reviewing numerous studies involving antimicrobial agents for the control of plaque and gingivitis, Marsh concludes that the use of “a zinc citrate/Triclosan dentifrice reduced plaque accumulation and gingivitis compared to a placebo paste.” The author further observed that “the ratio of anaerobiclaerobit bacteria and the proportions of Actinomyces species in plaque were also reduced.” Several studies extol the use of zinc citrate with triclosan (ZCT) as a plaque inhibitor system. Cumminslg found, in a 16-hour and 4-day plaque growth inhibition study, that ZCT inhibited plaque accumulation significantly more than either agent alone. The effect on the development of gingivitis was demonstrated in a 21-day experimental gingivitis study in which ZCT reduced the development of gingival bleeding sites by a significantly greater proportion than ZCT alone. This author states that “zinc and Triclosan employ multiple modes of antimicrobial action and these result in reduced growth, inhibition of glucose uptake and metabolism and modified virulence of periodontal pathogens.” He also suggests that the effects of zinc and triclosan are additive and complementary. When emphasizing the importance of preventive care for institutionally handicapped children and adults, two observations are most commonly reported: poor oral hygiene and a high prevalence of periodontal disease. Although the common strategy for plaque control is the mechanical removal of the material, frequent prophylaxis for the handicapped is often clinically impractical. Chikte et aLzO undertook a study to evaluate the effect of twice daily oral sprays of 2 ml chlorhexidine (0.2 % ) and 2 ml stannous fluoride (0.2%) as the sole oral hygiene measure to control plaque and gingivitis in handicapped children. The study involved 52 institutionalized mentally handicapped individuals (aged 10 to 26 years) who were divided into four groups participating in a g-week double-blind, randomized

THE

JOURNAL

OF PROSTHETIC

DENTISTRY

clinically controlled trial. The spray method was found to be easy to use and the responses of the staff and patients were positive. Stannous fluoride and chlorhexidine sprays used in this study were effective in reducing plaque and gingival scores and controlling subgingival microorganisms. All the same, long-term investigations are recommended “to explore the potential side effects and to demarcate the optimum therapeutic level of both stannous fluoride and chlorhexidine sprays.” DENTAL

EDUCATION

Following the assumption that dental school clinical training has a profound effect on the preventive strategies of young dentists in the early years of their practice, and frequent criticism that dental schools do not fulfill this responsibility adequately, Ripa and Johnsonzl reported a study of the graduates of one dental school from that school’s first 12 years of operation. Of the 305 students who graduated during that period, 181 are in general practice. Graduates were sent a 26-question inquiry concerning the patterns of practice and the use of preventive procedures such as oral hygiene instruction, sealants, preventive resin restorations, home fluoride rinses, home fluoride gels, dietary fluoride supplements, and diet analysis. The preventive method least practiced by the respondents was diet analysis and modification. Ninety-seven percent of the graduates responding to the survey provide oral hygiene instruction for all or most of their patients. Ninety-six percent of the general dentistry graduates who responded to this survey did not refrain from using sealants for all or most patients who require them. Seventy-five percent of respondents use preventive resin restorations for all or most of their patients who require them; however, 9.3 % did not use them at all. Of the three fluoride methods included in the survey, fluoride rinses prescribed by the dentists was the most commonly employed method; 76 % of the respondents prescribed such rinses. The use of home, or self-applied, fluoride gels had the lowest utilization of the fluoride methods in this survey. With these observations, the authors suggested that, in most respects, preventive practices taught in dental schools are pursued faithfully by dentists in their first dozen years of practice, and they concluded that at least this one school had successfully assisted its graduates in the development of a general preventive philosophy during their student tenure. “Considering the high rate of adoption of preventive practices by graduates of one dental school, it is apparent that dental schools have the potential of both teaching the particulars of preventive methods and encouraging their students to utilize them after graduation.” DENTAL Fluoride

CARIES

In 1991, a comprehensive review was made of fluoride’s benefits in preventing dental caries, and the possible risks attendant to the use of fluorides, including enamel fluoro141

JENDRESEN

sis. 22The research and policy “list of recommendations” in this report recommends that the Public Health Service continue to recommend the use of fluoride to prevent dental caries and that optimum fluoridation levels be described as 0.7 to 1.2 ppm in drinking water. Other recommendations are detailed in this report, and a series of research recommendations are included to encourage further study on all themes related to the use of fluoride. Use of fluoride caries-preventive

with

other agents

Studies have continued in which fluoride, a known caries-preventive agent, has been tested with other anticaries or antibacterial agents. Included during 1991 were the following studies. Any method that enhances the caries-inhibiting effect of dentifrices is important since dentifrices are available to so many people worldwide. In this study,23 the important combination was xylitol with sodium monofluorophosphate (MFP). After 3 years of use, there were no statistically significant differences between the different toothpaste groups concerning either caries development or the number of Streptococcus mutans and Lactobacill~s sp in the saliva. “However, children with no detectable approximal caries at baseline,who usedthe toothpaste with the xylitol-sorbitol mixture, showeda lower (p < 0.05) caries increment compared with children who used the MFP toothpaste with sorbitol alone.” is important becauseit deals A study by Schaekenet a1.24 with root caries,which is taking on more importance asthe population agesand becauseit comparestopical fluoride varnish treatments with topical chlorhexidine varnish treatments. After 1 year, both treatment groups had less new root caries than the nontreated control group. Rootsurfacelesion rehardening was recorded in the chlorhexidine treated group. Another study basedon the needsof older patients was reported by Keltjens et al.25Daily applications of a placebo gel, fluoride gel, and chlorhexidine-fluoride gel were made on the abutment teeth of patients with overdentures. After 18 months, caries development was reduced in the chlorhexidine-fluoride treatment group comparedwith the fluoride- and placebo-treated groups. Fluoride

anticalculus

dentifrices

A number of fluoride dentifrices alsocontain either soluble pyrophosphates or zinc compounds as anticalculus agents.Becausethe mechanismof action of fluoride is to promote the precipitation of calcium and phosphate (crystal promoter) and the action of anticalculus agentsis to inhibit the precipitation of calcium and phosphate (crystal inhibitors), it is important to know whether the presenceof anticalculus agentsin a fluoride dentifrice adverselyaffects the cariesinhibition of the dentifrice. In this 3-year clinical study,26there wasno difference in cariesincrementsof three groups of children using different fluoride anticalculus dentifrices compared with a control group using a 142

ET AL

fluoride dentifrice. It wasconcludedthat solublepyrophosphates or zinc compounds,added as anticalculus ingredients to dentifrices, do not interfere with the caries-inhibitory properties of the fluoride. Sealants A study by Simonsen27provided the longest period of study involving sealant application. In 1976 an autopolymerized white sealant was placed on first permanent molars of 200 children, aged5 to 15 years. Twenty-four subjects and 192 surfaceswere reexamined 15 years after the single sealant treatment. The sealant was completely retained on 27.6% of the pit and fissuresurfacesand partially retained on 35.4%. The sealantwascompletely missing on 10.9% of the surfaces,and 26% of the surfaceseither had been restored or were carious. In a study by Dennison et a1.,28newly erupting permanent molarswere treated with an autopolymerized sealant. Teeth were categorized according to their degreeof eruption and to the thickness of the sealant applied. After 36 months, molarstreated originally with the operculum covering the distal marginal ridge of the occlusal surfacehad twice the probability for retreatment as teeth not treated until the entire marginal ridge wasexposed.Sealant thicknessdid not affect the early signsof sealant failure. This study showshow the stageof eruption at the time of treatment affects the clinical successof sealants. The island of Guam instituted a school-basedfluoride mouth rinsing program in 1976.2gA clinic-based sealant program wasadded in 1984.In 1986,lO years after the beginning of the program, there was a reduction of 4.13 decayed, missing,or filled teeth (DMFs) per child. This representeda decline from 7.06 DMF at baselineto 2.93DMF surfacesper child in 1986.The combination of dental sealants and fluoride mouth-rinsing is an effective method of reducing caries in school children.2g Another report, by Mertz-Fairhurst et a1.,30showsthat carieswill be arrested beneath a properly placed sealant. ClassI lesionswere treated with minimal preparation and without caries removal. A sealed composite (CompS/C, Caulk) wasplaced over the caries.Carieswasarrested under the CompSlC restoration during the 4-year observation period. Other types of restorations were alsoevaluated in this study. Caries

prediction

studies

Sinceit isknown that the highestcarieslevelsin children are borne by approximately 20% of the population, a number of attempts have beenmadeto develop prediction modelsto identify the high-cariesrisk children before cariouslesionsdevelop. The following two reports fall into this category of study. Russellet a1.31studied salivary, clinical, and microbiologic factors with subsequent2-year caries increment in a group of 372 Scottish adolescents.They reported that the “caries increment was significantly correlated with previous caries experience, salivary buffering capacity, and JULY

1992

VOLUME

68

NUMBER

1

COMMITTEE

REPORT

counts of Lactobacillus sp, Streptococcus mutans, and Can&a sp.” They reported that significant improvements in the predictions were obtained when the results of more than one test were included with stepwise regression analysis. On an individual basis, with stepwise discriminant analysis, the caries increment group (low, medium, or high) was identified correctly in 49 % of all subjects, but this was reduced to 45 % if previous caries experience was excluded from the analysis. Graves et a1.32 analyzed multiple factors in caries prevalence from the University North Carolina caries risk assessment study. The baseline caries experience of approximately 5000 children in South Carolina and Maine was used as the dependent variable in caries risk assessment analysis. They cited the lack of consistent association of many variables, including microbiologic factors, but concluded that “some of these variables will contribute predictive power in the prospective study.” The importance of both these studies relates to research strategy, rather than the specific study outcomes per se.

Streptococcus

mutans

and caries

in children

Another study among many in recent years showed a correlation between salivary S. mutans levels and caries.33 Predentate infants do not harbor S. mutans. S. mutans appears with the eruption of teeth, and the concentration of S. mutans correlates with the number of erupted teeth. The concentration of S. mutans was more closely correlated with caries prevalence of the next year than that of the year when the salivary concentration of S. mutans was first evaluated.

Fluorosis Within the past few years, attention has focused on enamel fluorosis. A study by Evans and Stamm34 is important because it established the risk period for the maxillary permanent central incisors. Data on the prevalence of dental fluorosis in Hong Kong children in which the fluoride level in the drinking water was reduced from 0.8 to 0.6 ppm, were used to determine the period of greatest risk of developing fluorosis from a fluoride challenge during development of the maxillary permanent central incisor. It was concluded that for the maxillary permanent central incisor (1) the fluorosis risk is minimal to 18 months of age; (2) the maximum risk period occurs between 22 and 25 months; and (3) risk of fluorosis from continuous fluoride exposure will continue for up to 36 months beyond the peak period.

PERIODONTICS Epidemiology Several important epidemiologic studies were reported in 1991. The studies yielded varying results, due in part to analysis of different populations and the use of different measures for the presence of disease. Nevertheless, useful information concerning the prevalence of periodontal disTHE

JOURNAL

OF PROSTHETIC

DENTISTRY

eases was presented, although the figures reported should be considered as estimates. A national survey of the oral health of American children aged 5 through 17 years was conducted by the National Institute of Dental Research during the 198687 school year.35 The sampling frame for the survey consisted of all public and private schools in the United States, except Alaska. A multistage probability sample representing 45 million children was selected. More than 11,000 adolescents aged 14 through 17 years received a periodontal assessment. Approximately 0.53 % of adolescents nationwide were estimated to have localized juvenile periodontitis (LJP), 0.13 % to have generalized juvenile periodontitis (GJP) and 1.61% to have incidental periodontitis (loss of attachment ~3 mm on one or more teeth). The total number of adolescents is not trivial. Almost 70,000 adolescents in the United States were estimated to have LJP in 1986-87. More destructive GJP affected an estimated 17,000 and an additional 212,000 adolescents were estimated to have incidental periodontitis. The total prevalence of early onset periodontitis was 2.27%. Blacks were at a much greater risk than whites for all forms of early onset periodontitis. In a group of 5013 young male and female military recruits of varying ethnic origin, the prevalence of LJP was determined to be 0.76 % .36 Blacks again had a higher prevalence, 2.1% , than whites, 0.09 % . Several studies reported varying prevalences of early onset periodontitis in foreign populations. A study designed to compare the prevalence of marginal bone loss in two cohorts of 16-year-old adolescents born in 1959 and 1972, respectively, was conducted in Sweden.37 Bitewing radiographs from 400 subjects in each group were evaluated for the presence of bone loss defined as the distance from the cementoenamel junction (CEJ) to the alveolar crest >2 mm. The prevalence of such bone loss was 3.5% in both groups. No distinction was made for specific forms of early onset diseases. A study in Chile found a prevalence of LJP of 0.32% in a population of 2500 school children aged 15 through 19 years.38 LJP was found more commonly in the low socioeconomic groups. By contrast, a much higher prevalence was found in a population of 222 teenagers attending a private school in Sao Paulo, Brazil.3g This group had a relatively high socioeconomic background and received dental care on a regular basis through private dental clinics. Radiographic evaluations revealed 1.3% and 1.8% of the teens displayed features of LJP at 13 years and 16 years, respectively. In addition, 5.4% and 12.6% displayed radiographic bone loss consistent with incidental periodontitis at ages 13 years and 16 years, respectively. The prevalence of adult periodontitis was evaluated in a cross-sectional study of the U.S. employed population, consisting of more than 15,000 men and women representing 100 million employed adults aged 18 through 64 years.40 Assessments were made for gingivitis, gingival recession, and periodontal pocket depth at mesial and buccal sites of all teeth in randomly selected “half-mouths.” Mesial measurements were made from the buccal site with the probe 143

JENDRESEN

parallel to the long axis of the tooth as close to the contact point as possible. Loss of attachment ~3 mm at one or more sites was found in 16 % of 18 through 24-year-olds and 80% of the group aged 55 through 64 years, with a mean prevalence of 44 % for the total sample. More advanced attachment loss, ~5 mm, affected approximately 13 % of the population. Periodontal pockets were found in 14 % of the group, increasing from 6% at age 18 through 24 years to 18% at age 55 through 65 years. Recession ~3 mm also increased with age and was found in 16% of the group on an average of five sites. Most of the periodontal pockets were found interproximally, whereas recession was much more frequent on buccal surfaces. The results of this study indicate that many employed Americans older than 35 years have experienced significant periodontal attachment loss on at least 4 to 5 teeth. The prevalence and severity of periodontal pockets increase with age, in blacks, in people with less education, and those who have not visited a dentist in recent years. Having dental insurance was not associated with better periodontal health. The prevalence of periodontitis in the United States may actually be greater than that reported in the study because of limitations inherent in the evaluation of large numbers of subjects. The probing technique described, line-angle probing, is more easily standardized for use by multiple operators and for use over time but is less accurate than the method of angling the probe to reach the most apical midproximal depth of the periodontal pocket. A comparison of these two methods was done with use of the Florida probe system.*l The results indicated that for subjects with 4 to 8 mm pockets, midproximal measurements were approximately 1 mm greater than line-angle measurements for posterior teeth. Addition of 1 mm to the 4 mm data in the U.S. adult survey would increase the proportion of the population with significant pockets fourfold. Use of one probing method or the other depends on the use to which the measurements are to be applied. Line-angle probing has been considered a reproducible method and midproximal probing yields the best data on which diagnosis and treatment are based. In addition, another study showed that half-mouth examinations can be accurate and efficient in estimating mean scores for pocket depth and attachment loss but may underestimate the proportion of the population having selected levels of moderate or severe periodontitis by as much as 13 % .42 In an interesting report, the natural history of untreated periodontal disease in a group of individuals with poor oral hygiene and no access to dental treatment or advice was studied by use of a technique based on the condition of the interseptal bone. 43 The results indicated that periodontitis in Britain in medieval times was not as severe as formerly considered and was very similar to that of a British survey of the 1960s.

Diagnosis Periodontal probing and evaluation of radiographs remain the basis of periodontal disease diagnosis. The limi144

ET AL

tations of these techniques and the evaluation of additional diagnostic tests, both for the presence of disease and the prediction of future periodontal breakdown, continue to be areas of active research. In incipient periodontal disease, there is a lack of consensus regarding what constitutes crestal bone loss on a radiograph. The radiographic CEJ-crestal distance was determined for sites at which clinical attachment measurements indicate no attachment 10~s.~~ From these measurements it was concluded that no loss of crestal bone is consistent with a range of radiographic CEJ-crestal distance between 0.4 and 1.9 mm as evidenced on bitewing radiographs. Bitewing radiographs provide the most accurate image of crestal bone because of the usual ease of proper film alignment. It was noted that positioning errors of up to 10 % do not have a consistent deleterious effect on alveolar bone loss measurements of mandibular molars taken from enhanced digital images of bitewing radiographs.45 Radiographic changes, as seen in standard techniques, although useful to confirm bone loss, do not always correlate with the clinical parameters of disease. Bitewing radiographs taken at baseline and after 1 year in a group of 422 teenagers significantly underestimated the presence of periodontal destruction as compared with clinical measurements.46 In recent years, new imaging methods have become available that can reveal early density changes in the alveolar bone. One such system, computer-assisted densitometric image analysis, was evaluated and compared with probing attachment level (PAL) in 25 subjects with a history of adult periodontitis.47 Radiographic density change was seen in 38 % of sites compared with 6 % of sites demonstrating PAL ~2 mm. It is possible that this loss of density is indicative of small increments of continuing disease activity that are not reflected by the relatively high threshold of PAL or that the density changes may involve normal patterns of remodeling within alveolar bone unrelated to disease progression. In an effort to increase sensitivity in detecting active alveolar bone loss due to periodontitis, a scintillation camera method was assessed.48 The accuracy, sensitivity, and specificity of the quantitative gamma camera method for detecting sites of active bone loss, assessed relative to the longitudinal radiographic data, were 85 % ,90 % , and 19 % , respectively. This technique shows promise as a research tool for confirming the presence or absence of disease activity in longitudinal, prospective evaluations of diagnostic tests. Since periodontitis is an infection, microbiologic analyses have been evaluated for diagnostic use. Results to date have provided little additional information beyond those obtained in a routine clinical examination except in cases of LJP and rapidly progressive periodontitis. An analysis with DNA probes for putative periodontopathic microorganisms suggested that sites with the deepest probing depths and sites that bleed on probing were most likely to harbor these pathogenic species.4g JULY

1992

VOLUME

68

NUMBER

1

COMMITTEE

REPORT

The relationship between the quantity of specific subgingival microorganisms at baseline and subsequent attachment loss was examined in 38 subjects.50 The results of this study indicated that a number of microbial species were related to the risk of new attachment loss. It was not possible to determine that the species identified were the only or even the most important species conferring risk of periodontal attachment loss. The number of subjects in this study was limited and may not have included all forms of periodontal disease, only 14 subgingival species were evaluated, and control subjects with minimal or no disease were not included. To allow more widespread use of systemic antibody analysis in clinical settings, a rapid test for determining elevated antibody to periodontitis-associated bacteria was developed.51 This technique utilized dot-immunoblotting (DIB) on nitrocellulose paper with whole formalinized periodontal pathogens. Using peripheral capillary blood and the DIB, detection of elevated systemic antibody levels can be performed in approximately 2 hours. The DIB may be useful in assessing the host response to putative periodontopathic microorganisms. Temperatures in periodontal pockets were found to increase consistently with increase in pocket depth.s2 No attempt to correlate this increase with disease activity was made; thus the significance of this diagnostic tool is unknown. Measurement of periodontal pocket depth is at present the principal clinical method in periodontal diagnosis. The measurement of standard deviation error for loss of attachment evaluated with a periodontal probe was found to be 0.4 to 0.54 mm for individual sites.53 Because the variation in loss of attachment scores due to measurement error can often equal that due to actual changes in disease levels, more sensitive probes are desirable. This is especially true in clinical trials. Usually a level of 2 to 3 mm of probing attachment loss between sequential examinations has been used to define disease activity. This high threshold gives a high specificity but limits the ability to detect smaller degrees of disease progression, thus yielding a lower prevalence of disease activity. Use of an automated probe capable of measuring probing attachment levels relative to the CEJ with better than 0.2 mm accuracy found a prevalence of disease activity of 29 % with a 0.4 mm threshold compared with 2% at a 2.4 mm threshold.54 An evaluation of the association of baseline clinical parameters of periodontal disease with actual disease progression the following year in 271 untreated subjects revealed attachment loss increase 23 mm in 27% .55 Increased pocket depth, bleeding on probing, and sites exhibiting prior attachment loss were strongly correlated to subsequent attachment loss. Similar results were seen in a study of 21 subjects who exhibited disease progression after active periodontal therapy.@ The only measurement that showed a consistent correlation with change in attachment was pocket depth. Although bleeding and suppuration were not absolute indicators of disease progresTHE

JOURNAL

OF PROSTHETIC

DENTISTRY

sion, they were regarded as risk indicators for future attachment loss. Longitudinal bone loss ~2 mm occurred more often among sites showing an angular defect compared with sites with horizontal alveolar bone morphology.s7 Thus the presence of an angular bony defect entails an increased risk for further alveolar bone loss. Evaluation of gingival crevicular fluid (GCF) shows promise for prediction of disease activity and risk of attachment loss, but to date no specific test has reached the point of application to clinical practice. One study evaluated the volume and amounts of lactate dehydrogenase (LDH), arylsulfatase (AS), and neutrophil elastase (NE) in GCF collected over a B-week period in 11 young adults.5s A clear relationship between GCF volume and the gingival index (GI) was not evident. Site mean LDH, AS, and NE activity were all positively correlated with site mean GI. However, the variability in GCF volume and composition observed from sampling to sampling was sufficient to show that a large change from baseline values is required before a site may be said to have increased activity. A cross-sectional study analyzed the possible relationship between GCF elastaselike proteinase (ELP) levels and the periodontal clinical parameters or the presence of specific bacteria in subgingival plaque. sg A strong association was found between GCF ELP concentration and bacteria previously associated with advancing periodontitis, indicating that measurement of GCF ELP concentration may be useful in the evaluation of periodontal sites, especially those with little or no current tissue destruction. A longitudinal study monitored aspartate aminotransferase (AST) in GCF samples from 31 patients with mild to moderate periodontitis. Loss of attachment 12 mm was observed in 40 of 1536 sites.60 AST was elevated at these sites as well as sites with past attachment loss and sites with gingivitis in the absence of periodontitis. The inability of AST levels to differentiate active sites from those with evidence of inactive periodontitis or gingivitis render this test of questionable clinical significance. Two studies supported the concept that interleukin-l@i and interleukin-2,62 potent bone resorptive cytokines, are elevated at the site and in the sera, respectively, in patients with active periodontitis and thus may provide a sensitive laboratory test for assessing periodontal disease activity. Presently, increasing probing depth from values obtained following completion of active periodontal therapy appears to be the most reliable parameter for diagnosing active periodontal disease. Multiple recordings over time are required to improve predictability. When manual probing is performed, 2 to 3 mm change in probing attachment level is necessary between examinations before diagnosis of active disease can be assured. In the future, further technical development of diagnostic aids including electronic probes, digital radiographic image processing, and evaluation of GCF components will improve sensitivity and influence diagnostic procedures in clinical practice. 145

JENDRESEN

Etiology

and pathogenesis

An excellent, well-designed longitudinal study concerning the etiology and pathogenesis of active adult periodontitis was published in 1991. 63 Twenty adult periodontitis subjects were examined every 2 to 4 months and microbiological samples were collected and cultured when loss of attachment 22 mm was detected. Similar sites with no progression of attachment loss were also sampled in the same subjects. The only species that were detected in one or more samples from all subjects with active sites were Wolinella recta, Fusobacterium nucleatum, and Peptostreptococcus micros. Porphyromonas gingivalis (aka Bacteroides gingivalis) and nine other taxa were isolated from one half or more of the subjects with active sites. The composition of floras of all other periodontitis samples was significantly different from that of subjects with healthy gingiva. The composition of microflora from sites in subjects with gingivitis was intermediate between that of subjects with healthy gingiva and that of active and control sites in adult periodontitis subjects. The authors conclude that the species responsible for the original initiation of the disease should include those present before extensive tissue destruction has occurred, as seen in health or gingivitis or periodontitis. In addition to Eubacterium brachy, E timidum, Fusobacterium nucleatum, Lactobacillus DOl, P micros, Prevotella intermedia 8944, Selenomonas sputigena, W recta, and Treponema socranskii, which are detected in low numbers in healthy gingiva, this would includePeptostreptococcusanaerobius,EubacteriumDll, Fusobacterium alocis, E nodatum, Treponema pectinovorum, and the large treponeme found in gingivitis but not in healthy gingiva. F nucleatum and E nodatum were considered prime suspects in the initiation of periodontal disease. Several other species may contribute to tissue destruction once gingival irritation has been produced. The authors suggest that colonization of teeth, with actinomyces and streptococci organisms, which coaggregate with F nucleatum and other species to produce tissue irritation, bleeding, and serum exudate, which in turn stimulate Porphyromonas and Prevotella species and a number of other species associated with tissue destruction by direct or indirect means, appears to be the most likely scenario for the development of human periodontitis. In a cross-sectional study designed to relate clinical characteristics at a site to the frequency of detection, absolute counts, and proportions of 14 selected subgingival species, it was found that total viable counts increased with increased pocket depth.64 Of interest, 20% of sites with deep pockets or attachment loss did not harbor detectable levels of any of the 10 suspected pathogens. Explanations for this finding include the possibility that deep pockets reflected past damage and harbored low numbers of pathogens tested or other pathogens not sought in this study. A study of the predominant subgingival microflora in 24

146

ET AL

patients with periodontal disease, who were 18 to 60 years of age in Santo Domingo, Dominican Republic, revealed fewer spirochetes and markedly more enteric rods in adult periodontic lesions compared with those in the United States.65 If enteric rods act as periodontal pathogens in susceptible Santo Domingo patients, then enteric rodassociated periodontitis may represent an exogenous infection due to inadequate sanitary conditions. This possibility may help explain the high prevalence of periodontitis in certain third world countries. In a microbiological evaluation of the predominant cultivable bacteria associated with juvenile periodontitis (JP) in China, Eubacterium species were found in significantly higher frequencies and proportions compared to healthy sulci in control patients.@ Actinobacillus actinomycetemcomitans was not detected in any samples and it thus appears that this species is not associated with JP in China as it is in the United States. Although this study included only 15 JP patients, it was concluded that JP might be initiated by a variety of redundant bacteria rather than one specific microorganism. The possible associations between the age of the subject with periodontitis and the distribution of A actinomycetemcomitans and Pgingivalis were examined by use of DNA probes in a large population. ” A actinomycetemcomitans was found more frequently and at higher levels in younger subjects than in subjects aged 30 years and older. In contrast, P gingivalis prevalence and levels were higher in the older age groups than in those below 30 years. Approximately a third of the juvenile subjects did not harbor detectable levels of A actinomycetemcomitans~ providing further evidence that other pathogens may be involved in juvenile periodontitis. It has been suggested that severe gingival inflammation and attachment loss are often associated with HIV seropositive patients. (A study evaluated the periodontal status of such patients without biasing the data towards those presenting to dentists with oral problems.68) No significant differences could be found in the gingival or periodontal status of subjects who were HIV seropositive versus those with AIDS. Periodontal health of the subjects was similar to that of the general population. This would indicate that although HIV-gingivitis and HIV-periodontitis have been documented in HIV-infected patients, the frequency of affected individuals may be less than previous reports would suggest. Findings from two studies6s,70 suggest that there is no difference in the subgingival microflora between chronic periodontitis in systemically healthy patients and HIV patients with periodontitis. However, the severity of periodontal disease correlated with the progression of HIV infection, indicating a relationship between impaired host defense mechanisms and periodontitis.71 By contrast, in 230 military personnel who were HIV seropositive, no such clear relationship was seen for periodontitis, although the prevalence of viral and fungal infections in the

JULY

1992

VOLUME

68

NUMBER

1

COMMITTEE

REPORT

mouth clearly related to the degree of immune dysfunction.72 Acute necrotizing ulcerative gingivitis (ANUG) has been generally considered as a gingivitis. Clinical impressions suggest that periodontal attachment loss is one of the sequellae of this disease. Results of a study in young patients indicated that attachment loss is greater in ANUG-affected sites than in unaffected sites.73 Gingival hyperplasia, similar to that seen in patients taking phenytoin, has recently been seen in patients taking nifedipine, a long-acting vasodilator widely used for cardiotherapy. Regression is seen with discontinuation of the drug. Clinical findings and the results of in vitro experiments with nifedipine suggest that local inflammatory factors are essential for the onset of hyperplasia and that nifedipine affects the inflamed tissues indirectly.74 Therefore, strict plaque control following surgical reduction of the hyperplastic gingiva is necessary to prevent recurrence in patients for whom substitution or withdrawal of nifedipine is clinically inadvisable. Previous reports have indicated that mucosal and periodontal lesions occur in patients suffering from Crohn’s disease (CD) and ulcerative colitis (UC). The findings of an investigation of 107 consecutive patients seeking treatment for inflammatory bowel disease suggest that patients afflicted with CD or UC are no more susceptible to severe periodontal disease than the general population.75 Based on the prevalence and serotype distribution of A actinomycetemcomitans within families, intrafamilial transmittance was suggested in a recent study.76 However, results of an epidemiologic survey on the periodontal status of young adults in a school with a relatively high number of subjects showing loss of attachment (18 out of 87) indicated that bacterial cross-infection did not occur among subjects in this schoo1.77 Data from a study using DNA probes did not support the potential issue of contamination by the subgingival flora from adjacent teeth.4g Even though specimens were collected after a thorough periodontal probing, no increased levels of any of the species were found in sites immediately adjacent to sites with the highest concentration of pathogens. In an interesting study, probing depth, clinical attachment loss, gingivitis, and plaque were assessed in 110 pairs of adult twins, including 63 monozygous and 33 dizygous twin pairs reared together and 14 monozygous twin pairs reared apart. 78 The purpose of this study was to examine the relative contribution of environment and host genetic factors to clinical measures of periodontal disease. A significant genetic component was identified for all parameters. Heritability estimates indicated that 38 % to 82 % of the population variance for these parameters may be attributed to genetic factors. Although bacterial plaque is generally accepted as the primary etiologic agent in gingivitis and periodontitis, the severity of periodontal diseases also depends upon the host’s immunologic response to

THE

JOURNAL

OF PROSTHETIC

DENTISTRY

bacterial challenges. Variability in host response may be a component of a genetic predisposition to periodontal disease. In support of this concept, data suggest that patients with rapidly progressive periodontitis do not produce protective levels of biologically functional antibody, a possible genetic deficiency, during the course of the natural infection.7g However, it appears that periodontal therapy may stimulate proper production. The findings of a cross-sectional study of 511 adults aged 20 to 64 years support the current hypothesis that age-related alterations in the periodontium may not inevitably be manifested as loss of probing attachment or alveolar bone.80 This demonstrates that the increase in prevalence and severity of periodontal disease with age must be the result of a prolonged exposure of the periodontal tissues to plaque instead of the consequences of age. Results of two studies contribute further support to the possible role of interleukin-1P, interleukin-2, and interleukin-4 as important mediators in the pathogenesis of periodontitis.61f 81 In a study of 215 impacted mandibular third molar removals performed on 144 patients aged 16 to 53 years, predictors of postoperative intrabony defects (IBD) on the distal surface of the adjacent second molar were determined 2 years postsurgically. 82 Eighty percent of the cases with deep IBD showed preoperative absence of supporting bone exceeding 4 mm on the distal surface of the adjacent third molar. Deep IBD appeared three times more often after mandibular third molar removals in individuals older than 25 years of age. Mouth breathing, increased lip separation, and decreased upper lip coverage at rest were all associated with higher levels of plaque and gingival inflammation in a study of 201 schoolchildren aged 11 to 14 years.83 The influence of mouth breathing was restricted to palatal sites, whereas lip coverage influenced gingival inflammation at both palatal and labial sites. Gingival recession localized to the mandibular incisors was observed at yearly intervals over 3 years in 28 children aged 6 to 13 years. 84 Teeth undergoing orthodontic treatment and teeth with restorations or fractures below the gingival margin were excluded. Gradual reductions in the amount of recession were noted in all children except one with a severely malpositioned tooth. This finding suggests that developmental changes in the dentition during growth may influence the potential for improvement of gingival recession. Further preventive treatment by gingival grafting in this part of the dentition may not be necessary and should be postponed until any spontaneous improvement has taken place, except in selected cases and those undergoing orthodontic treatment. Improvement after the completion of growth, or course, should not be expected. The association between smoking and loss of periodontal bone height was investigated in 210 Swedish dental hygienistss5 The results suggest that loss of periodontal

147

JENDRESEN

height is related to smoking and that the difference in bone loss is not correlated with a difference in plaque scores.

Pharmacologic

therapy

The effects of various antimicrobial agents administered either systemically or locally by different means were evaluated in studies reported in 1991. In a study of 27 patients with a history of periodontal abscesses or loss of attachment despite active periodontal therapy, consistent with a diagnosis of refractory periodontitis, 100 mg of doxycycline daily or a placebo for 3 weeks was given in a double-blind, randomized clinical trial. Clinical measurements and microbial analyses were performed at intervals of 1 week and 7 months after completion of the drug regimen. Patients treated with doxycycline exhibited improvements in attachment level whereas the placebo group continued to lose attachment. Doxycycline demonstrated profound antimicrobial activity at 1 week, whereas at 7 months there was repopulation of pockets with putative pathogens that did not lead to recurrence of active disease. Thus the long-term clinical improvement observed in the doxycycline group was not well explained by the antimicrobial activity of this drug.86 Four patients with a mean age 14 years were examined 1 to 4 years after the completion of a single B-week course of tetracycline, one gram per day, for treatment of LJP. The results suggested that (1) early identified lesions of LJP can be effectively treated with 6 weeks of tetracycline therapy alone; (2) decreases in pocket depth, gains in clinical attachment, and repair of alveolar defects remain stable up to 4 years after antibiotic therapy; (3) clinical and radiographic improvement continues over time and may lead to complete resolution of some lesions; and (4) the reparative and regenerative potential of the periodontium in early onset of the disease in young individuals may exceed that observed in chronic adult periodontitis.87 Six adult patients treated with tetracycline, one gram per day for 3 to 4 weeks, both alone and in combination with other forms of periodontal therapy demonstrated more dramatic regeneration than that shown previously with more conventional forms of periodontal therapy in areas of acute or aggressive forms of adult periodontitis.88 Both of these studies are case reports without controls and thus interpretation of the results is limited. A potential for benefit from tetracycline in selected cases, however, is apparent. Systemic metronidazole given 250 gm t.i.d. for 7 days in conjunction with debridement by closed approach was compared with debridement alone.8g The results suggested that the use of metronidozole reduced the number of teeth per patient requiring periodontal surgery and that this effect may be maintained for up to 2 years. Efforts to develop an effective means of local delivery of a sustained therapeutic level of antimicrobial agents have continued to yield some promising reports. Controlled delivery systems have been developed for placement within the periodontal pocket to create a longer duration of effec-

148

ET AL

tive concentration at a lower dosage without dependence on the substantive characteristics of a given drug. A multicenter trial tested the effectiveness of locally delivered tetracycline for treatment of periodontitis.gO Local delivery was provided by 0.5 mm diameter ethylene vinyl acetate copolymer fibers loaded 25% with tetracycline, placed in periodontal pockets, and maintained by an adhesive for 10 days. A total of 113 subjects at five centers participated in the study. Four nonadjacent teeth with 6 to 10 mm pockets that bled on probing were selected in each subject and randomly assigned to one of four test groups: (1) tetracycline fiber; (2) control fiber; (3) scaling and root planning; or (4) untreated. Clinical response variables were measuredgl and levels of six bacterial species were determined by DNA probe analysis. g2 Pocket depth reduction means for tetracycline fibers compared with scaling were 1.02 mm versus 0.67 mm. Bleeding on probing was reduced from 95.3% of sites to 49.5% for the tetracycline fiber group compared with a reduction from 93.5% to 73.8% for the scaling group. It was suggested that the pretreatment of all sites in each group by supragingival scaling and polishing diminished the apparent benefit in the scaling group and that one should not infer that scaling and root planing is not a useful means of therapy. The authors stated that scaling is used for the removal of calculus and other deposits and tetracycline fiber therapy is used for the control of local infection. It was curious, then, that tetracycline fibers and scaling both reduced the number of sites in which monitored species were detected. The fiber control and untreated sites showed no reductions. The generalized reduction of bacterial load, which varied from 36% to 86% reduction depending upon the species, is consistent with the broad spectrum activity of tetracycline and the nonspecific nature of subgingival scaling. Both DNA probe and cultural methods indicated comparable levels of suppression of monitored sites after tetracycline fiber therapy and subgingival scaling.g3 A similar study described the results on selected clinical and microbiological parameters obtained by periodontal treatment with tetracycline fibers placed into pockets ~6 mm exhibiting bleeding on probing, both alone and in combination with scaling. g4 Controls included sites treated by conventional scaling alone and untreated sites in a four-quadrant split-mouth design. The study included 95 teeth in 10 subjects. All treatments resulted in changes indicative of effective therapy. Pocket depth was reduced approximately 2 mm, with none of the treatments differing significantly. The results were the same whether analyzed on a site basis or a subject basis. The findings suggest that tetracycline fiber therapy was at least as effective as scaling over a short term (42 days). Significant reduction of total bacterial counts and the percentage of black-pigmented Bacteriodes was also achieved by all three treatments. In view of the short observation period, long-term studies will be required to elucidate the true value of local drug delivery in the treatment of periodontal disease.

JULY

1992

VOLUME

68

NUMBER

1

COMMITTEE

REPORT

Class II furcations in 46 maxillary and mandibular molars in 16 patients with generalized periodontitis were treated randomly with either (1) one root planing treatment (RP); (2) four consecutive administrations of tetracycline collagen film insertions at l-week intervals (tetracycline); or (3) both of these treatments (RP plus tetracycline).g5 Untreated sites served as controls. The results at 8 weeks showed significant decreases in probing depth for both the RP and RP-plus-tetracycline groups. Tetracycline film alone had no effect on probing depth. A reduction in bleeding on probing and a probing attachment gain were noted in the RP-plus-tetracycline group. The findings demonstrated that RP is effective in the treatment of class II furcations and that the short-term effects are enhanced by local administrations of tetracycline films, A controlled-release insert containing a synthetic antibiotic, ofloxacin, was tested alone or in combination with subgingival debridement and evaluated microbiologically in 27 patients with chronic periodontitis.g6 Comparison was made with mechanical debridement alone controls. The results indicated that the subgingival controlled release of ofloxacin could have significant effects on both the qualitative and quantitative changes in the subgingival microflora. However, the subgingival scaling and root planing alone was effective in eliminating the subgingival microflora. The combination of the two treatments produced no statistically significant additional benefits. An in vitro study demonstrated the long-lasting substantivity of doxycycline hydrochloride on periodontally diseased root surfaces and supports the concept of using root surfaces as a substrate for the deposition and slow release for local tetracycline delivery.g7 The short-term bactericidal effect of 2 % chlorhexidine (CHX) gel and 4% stannous fluoride (SnFls) gel was determined in 40 periodontal pockets 30 minutes after subgingival application. g8 Both gels produced a 99% reduction of the subgingival microflora. In a study over a period of 36 weeks, the clinical and microbiological effects of locally applied 2 % CHX gel, 4 % SnFls gel, 1.25 % amine fluoride gel, or placebo gel were studied in 40 periodontal pockets in 10 patients. gg Statistical analysis of the bacteriological and clinical examination data failed to demonstrate any significant difference between the groups. Thus, subgingival application of any of the tested gels did not augment the effect of mechanical debridement during the experimental period of 36 weeks. By contrast, a study of 10 patients over 2 years suggests that the use of subgingival sustained-release CHX in an ethyl cellulose-based dosage form shows promise in long-term maintenance therapy following initial debridement in periodontal pockets ~5 mm.ioO An in vitro study designed to determine the effect of CHX on the attachment of human gingival fibroblasts to root surfaces indicated that exposure of root surfaces to CHX significantly inhibits subsequent fibroblast attachment that may interfere with regeneration of the periodontium.lol It is possible that the antimicrobial benefit of

THE

JOURNAL

OF PROSTHETIC

DENTISTRY

CHX outweighs the cytotoxic side effects in wound healing in certain clinical applications, thus accounting for the generally favorable results obtained in multiple clinical studies. The effects of mouthrinse and toothpaste formulations on plaque and gingivitis continue to be evaluated. Chlorhexidine remains the most effective agent to date, although some benefits have been demonstrated with other agents. In a B-month double-blind parallel, placebo-controlled clinical trial involving 120 subjects, twice daily use of a sanguinaria and zinc chloride containing dentifrice with and without fluoride in combination with a sanguinaria and zinc chloride containing mouthrinse resulted in less plaque accumulation, less gingival inflammation, and less bleeding on probing when compared with placebo preparations of the same products, which was statistically significant.lo2 However, the actual difference in scores from baseline values, while statistically significant, were of slight magnitude and of questionable clinical significance. A double-blind cross-over study evaluated the prebrushing rinse Plax (Oral Research Laboratories, New York, N.Y.) or placebo rinse in 10 subjects performing a standardized poor brushing technique without toothpaste.lo3 No significant differences were noted between placebo and Plax for effect on plaque growth. Similarly, cetyl pyridinium chloride mouthrinse, when compared with placebo, offered no adjunctive benefits as a prebrushing rinse in the reduction of plaque and gingivitis.lo4 It was reported that although triclosan and sodium lauryl sulfate (SLS) provide some persistence of antimicrobial activity in the oral cavity when used at a relatively high dose, the addition of triclosan to an SLS toothpaste would impart little additional antimicrobial activity against salivary bacteria.lo5 A cross-over comparative measure of antimicrobial persistence after oral rinsing with either 0.12 % CHX (Peridex, Procter & Gamble, Cincinnati, Ohio) or 0.2% CHX (Corsodyl, ICI Pharmaceuticals, Macclesfield, Chelshire, England) produced similar large and prolonged reductions in salivary bacterial counts during a 7-hour period.lo6 Rinsing with 0.12% CHX before scaling and root-planing procedures was shown to be effective in reducing salivary bacte.. rial levels even in the presence of blood and debris.lo7 Of interest, subgingival irrigation with 0.12 % CHX before instrumentation did not decrease the incidence of bacteria resulting from scaling and root planing inflamed periodontal pockets.ro8 In addition, the irrigation procedure itself, whether with water or CHX, was shown to cause a similar incidence of bacteremia as did scaling and root-planing. Transient bacteremia is an acknowledged sequela to dental manipulation and is not known to pose risk to healthy patients. Observations, from an in vitro study that tested CHX for its ability to inhibit a wide range of glycosidic and proteolytic enzyme activities produced by putative periodontopathic microorganisms, support the hypothesis that CHX exerts a bacteriostatic effect in vivo, in part by reducing the ability of dental plaque bacteria to degrade 149

JENDRESEN

host-derived proteins and glycoproteins that normally provide essential nutrients for bacterial growth.log Adjunctive use of CHX solution was found to be clinically effective in reducing plaque and gingivitis in lymphoma patients receiving cytostatic drugsno and in institutionalized mentally handicapped subjects.lll Aminestannous fluoride solution and stannous fluoride solution, respectively, were found to be effective, but to a lesser degree in these studies. Rinsing with 0.12% CHX was effective in reducing the recurrence of gingival hyperplasia associated with the administration of cyclosporine in a case report1i2 It also had a significantly greater effect in reducing putative periodontal pathogens compared with water rinsing in 30 patients analyzed during fixed prosthodontic procedures.l13 However, when the data were analyzed in this latter study, the differences were not impressive. Analysis of clinical parameters in this same group of 30 patients during the same time period reportedly showed significantly reduced plaque levels and significantly improved gingival health compared with the control patients.r14 These differences, however, were influenced by higher baseline scores for the CHX group than the control group. The final gingival scores for both the CHX group and the control group were essentially equivalent. It is not known what effects would have been shown had the baseline scores been equal. In a 13-month trial in beagle dogs, naproxen, a nonsteroidal antiinflammatory drug (NSAID), was found to significantly inhibit alveolar bone 10ss.l~~ Its effect in reducing periodontal disease activity in humans was assessed in 15 patients with rapidly progressive periodontitis in a double-blind study.l16 Initial treatment by scaling and root planing was followed by 500 mg naproxen or placebo b.i.d. for 3 months. While there was no significant difference between groups regarding change in probing attachment level or gingival index, there was a significant difference in change of alveolar bone height as determined by digital subtraction radiography. The changes were small, a 0.14 mm mean loss of bone height for the placebo group compared with a 0.24 mm gain for the naproxen group. The efficacy of longer term naproxen administration as an adjunct in the treatment of periodontal diseases will require further investigation. The NSAID piroxicam, topically applied, inhibited developing gingival inflammation in beagles compared with placebo-treated dogs.l17 The percentage of bleeding sites was significantly reduced although the difference in gingival indices was less impressive, 0.90 experimental versus 1.2 control. The clinical significance of this difference is unknown and further research is needed to delineate the possible role of piroxicam in the treatment of periodontal diseases in humans. The reported benefit of folic acid supplementation on the recurrence of phenytoin-induced gingival overgrowth after gingivectomy was tested in eight subjects.lls Although the treatment group had less recurrence of gingival overgrowth, the mean differences from the control group was 150

ET AL

6% to 7% and the authors stated that clinically, this difference was not readily evident. An observed plaque growth-inhibiting effect of a hydrogen peroxide-releasing chewing gum was found to be of limited clinical significance.llg Nonsurgical

therapy

A trend toward less damaging methods of root surface debridement has evolved in recent years. An in vitro study showed that after 12 working strokes with a clinically appropriate force of application, only a thin layer of root substance, 11.6 pm, was removed by an ultrasonic scaler (Cavitron 2002 with TFI-1000 tip, Dentsply International, York, Pa.), compared with much greater losses with a sonic scaler (Titan-S, Star Dental Manufacturing Co., Valley Forge, Pa.), 93.5 ym; a curet, 108.9 pm; and fine-grit diamond burs, 118.7 pm. lzo Substance loss as measured in this study may not represent loss of root surface under clinical conditions and the findings should be viewed with caution. The magnitude of forces used during scaling and root planing procedures was shown to be an important factor in the amount of root substance removed per stroke.121 With an increasing number of strokes, the amount of substance removed became less, apparently the result of dulling of the curets after approximately 20 strokes. The in vitro effectiveness of a 13/14 curet and Cavitron scaler (Caulk) with either a P-10 tip or a diamond-coated P-10 tip (Dentsply International) was compared.‘22 Root surfaces were instrumented to visual or tactile smoothness. Analysis revealed that all mechanical methods were essentially equal in effectiveness for plaque and calculus removal. Complete removal of cementum was rare. The combination of an ultrasonic unit and delivery of a chemotherapeutic agent may be an effective treatment in view of the tip’s ability to remove plaque and calculus, disrupting the subgingival microbial environment, and possibly exposing more organisms to the antimicrobial effect of the subgingival irrigant. A Cavitron scaler with an EWPP tip (Dentsply International) provided this technique and was evaluated for effectiveness.lz3 It was found that a minimum dispersion of the medicament lateral to the tip required overlapping strokes to insure dispersion of medicament throughout the subgingival area. Portions of the subgingival area inaccessible to the ultrasonic tip will thus also be inaccessible to a chemotherapeutic agent delivered by this system. In an evaluation of short-term effects of nonsurgical periodontal therapy, 68 adult patients with moderate to advanced periodontitis underwent hygienic phase therapy including oral hygiene instruction, scaling and root planing, and elimination of plaque retentive factors such as overhanging restorations in a sequence of four to six appointments. 124 Subgingival instrumentation was completed in all sites and effectiveness of oral hygiene procedures was monitored. During a period of 3 to 5 months after active therapy, professional tooth cleaning was per-

JULY

1992

VOLUME

68

NUMBER

1

COMMITTEE

REPORT

formed at 4-week intervals. Results showed that sites with initial probing depth of 4 to 6 mm had a mean probing depth reduction of 1.03 + 1.04 mm and a mean clinical attachment gain of 0.69 f 1.43 mm. Both closed and open debridement in class II facial furcations were found to be successful in controlling inflammation, with no significant difference found between the two approaches for plaque index, gingival index, and gingival fluid index. iz5 There were also no significant differences for changes in pocket depth or probing attachment levels at any time period from baseline to 16 months. The reduction in pocket depth was approximately 1 mm for each group from a baseline of approximately 6.5 mm. The clinical effects of closed root planing (CRP) compared with root planing following surgical papilla reflection (SRP) augmented by fiber optic illumination were evaluated over a B-month period.126 No significant differences were noted between treatment types for clinical attachment level at any examination period. Significantly greater mean probing depth reduction occurred after SRP than CRP after 6 months. This greater reduction appeared to be primarily a function of surgical thinning and apical placement of the papillae. Posttreatment data collection after active nonsurgical therapy is necessary to evaluate the response to therapy and to determine the possible need to provide additional nonsurgical or surgical therapy. The therapist must make a clinical judgement to determine whether a site or sites are likely to progress without additional therapy. Definitive criteria are needed to aid in such an evaluation and data are being generated toward this end. In an evaluation of seven patients over 2 years following initial therapy, it was determined that persistent bleeding combined with either a deep residual probing depth or increase in probing depth are useful indicators in the identification of progressive periodontitis sites.127 Seventy-five patients with adult periodontitis were followed up for 6 months after a single 1 to 2 hour appointment of scaling and root planing to identify factors associated with progressive attachment loss.i2s Baseline mean attachment level, baseline mean probing depth, and the percentage of sites exhibiting bleeding on probing were all related to additional attachment loss. The age of the patient was also a risk indicator. In other words, patients with existing severe periodontal disease and patients over the age of 60 years were at greatest risk for further periodontal breakdown after scaling and root planing. Surgical

regenerative

therapy

Studies in this area continue to evaluate use of both resorbable and nonresorbable barrier membranes for guided tissue regeneration (GTR), bone autografts, allografts and alloplastic materials, root surface biomodification, coronal anchoring of flaps, and combinations of these procedures. An investigation of the clinical efficacy of use of a GoreTexmembrane (W.L. Gore and Associates, Flagstaff, Ariz.)

THE

JOURNAL

OF PROSTEETIC

DENTISTRY

after open-flap debridement compared with open flap debridement alone in the treatment of maxillary furcation defects in 17 patients with paired defects found no statistically significant differences between groups for probing depth reductions, clinical attachment gains, or resorption of alveolar crest height. 12g Interproximal furcation response was generally minimal, indicating that use of barrier membranes for GTR in maxillary molar class II furcations has limited application when contrasted against other studies that have found this technique efficacious for mandibular furcations. A comparison of the healing process of GTR using either a resorbable membrane Vicryl (Ethicon, East Brunswick, N. J.), or a nonresorbable membrane, Gore-Tex, for treatment of defects created in beagle dogs found that both types of membranes enhanced new attachment.130 The Vicryl membrane sites showed regenerative values less than those of the Gore-Tex membrane sites but significantly greater than the controls. In an uncontrolled report of treatment of 11 sites in 10 patients, Vicryl mesh was used alone in three sites and along with bone allograft in eight sites. 13r Radiographic examination and bone sounding indicated improvement in the treated areas, suggesting a possible benefit from this reasonable, membrane. The clinical response of GTR with a synthetic wound dressing, Biobrane (Winthrop Pharmaceuticals, New York, N. Y.) in the treatment of 15 mandibular and four maxillary class II furcation pairs in 19 subjects was evaluated by reentry at 6 months after operation.132 In contrast to other studies of barrier membranes, this synthetic wound dressing yielded no clinically quantifiable benefit over surgical debridement alone. Histologically observed new attachment in suprabony lesions treated by a combination of debridement, barrier membrane, and coronally anchored flaps was reported in four lesions involving mandibular incisors in one patient.lY3 Such new attachment was not seen in parallel sites in another patient in which surgical debridement and coronally anchored flaps without membranes were employed. The degree of new attachment was limited, and variations of new attachment were seen between sites and within a site. Yet, the histologic responses support the concept that, biologically, supracrestal new attachment is possible in the human model. In a study of four vertical lesions involving three teeth in two adult patients with severe periodontitis, treated by surgical debridement, osseous grafting with demineralized, freeze-dried bone allografts (DFDBA), Gore-Tex membranes, and coronal suturing of flaps, histologic crestal osteogenesis was seen in association with cementogenesis. 134Mean initial probing depth was 9.4 mm compared with mean postsurgical probing depth of 4.9 mm. Mean gain in probing attachment was 3.6 mm. The combination of techniques did not lead to enhanced periodontal regeneration over that seen when either a barrier membrane or DFDBA was used alone. In contrast, a study evaluating the use of DFDBA combined with a Gore-Tex membrane in the treatment of 15 pairs of class II or III 151

JENDRESEN

molar furcations compared with the barrier technique alone found statistically significant improvement in probing depth reduction and clinical attachment gain, favoring the combined technique.135 Evaluation by reentry at 6 months after operation found a distinct difference for both horizontal and vertical bone repair, favoring the use of DFDBA in combination with the barrier membrane. An evaluation of 27 mandibular class III furcation defects in 27 subjects was conducted using a GTR technique that included citric acid (CA) root conditioning, and coronally positioned flaps secured by crown-attached sutures.ls6 Thirteen defects received DFDBA. No barrier membranes were used. No statistically significant differences were observed between defects treated with and without bone grafts at 6 months after operation. Mean vertical probing reduction and mean clinical attachment gain in the furcation were 2.6 mm and 2.2 mm for the nongrafted sites and 1.9 mm and 1.5 mm for the grafted sites. Residual probing depth was approximately 5 mm for each group. In an evaluation of 18 intrabony defects in i6 patients treated by surgical debridement and placement of Gore-Tex membranes with and without CA root demineralization, it was concluded that the CA root-conditioning did not enhance gains in attachment or bone leve1.137 Use of the membranes did result in predictable and clinically significant improvement in attachment levels and bone fill, with 72% of the sites showing more than 50% defect fill. Root surface resorption as a response to CA demineralization or as a part of the regenerative phenomenon appeared to limit migration of the junctional epithelium in a histologic evaluation of six suprabony pockets in two adults treated with surgical debridement, CA root demineralization, and coronal positioning of the flaps.138 The authors concluded that comparing clinical and histologic healing responses in human suprabony lesions when either coronal anchorage and barrier membrane or coronal anchorage and CA root demineralization were used showed similar responses with both techniques. The number of human sites studied histologically were, of necessity, extremely limited and do not permit statistical projections of significance, although the results were reported to appear clinically dramatic. Other reports evaluating root surface biomodification found that although CA treatment of cementum from normal roots appeared to result in the exposure of fibrillar collagen substrate, periodontitis-affected cementum was not appreciably altered in appearance.13g CA treatment of the root surface in conjunction with GTR in periodontal therapy did not seem to enhance root resorption.140 An inhibitory effect on root resorption by SnFlz could not be disclosed in this same study. After a 5-minute application of 0.5 o/c solution of tetracycline (pH = 3.2), removal of the smear layer and exposure of the underlying collagen matrix was incomplete.141 The concentration used was because of the relative insolubility of tetracycline and the inability to achieve a higher concentration without the tetracycline

152

ET AL

precipitating out of solution. The addition of CA root demineralization and fibronectin application in GTR therapy with Gore-Tex membranes in naturally occurring periodontal defects in beagle dogs did not enhance connective tissue and bone regeneration.142 The addition of tetracycline to allogenic freeze-dried bone grafts increased and hastened new bone formation in artificial bone defects in baboons.143 One mechanism may be the aid in demineralizing this type of bone allograft, and thus the benefit of adding tetracycline to DFDBA is questionable. Short-term results suggested that a composite graft of tricalcium phosphate, plaster of paris, and doxycycline may promote partial fill of furcation defects.144 Results of a study of human periodontal defects showed that osteogenin, a bone inductive protein, when added to DFDBA produced results similar to the use of DFDBA alone.145 Renewed support for synthetic alloplastic implant materials is provided by studies reported in 1991. The use of hydroxyapatite (HA) implant in nine patients resulted in a greater degree of hard tissue fill-in of periodontal osseous defects compared with debrided, nongrafted controls at 2 years postsurgery when evaluated by computerized densitometric analysis of standardized radiographs.146 Histologic evaluation of a tooth removed due to root fracture revealed that previous treatment of a periodontal intraosseous defect with Interpore 200 material (Interpore International, Irvine, Calif.) resulted in new connective tissue attachment to new cementum coronal to the area that was root planed.147 From an ultrastructural study conducted on biopsies taken at 6 and 12 months after implantation of three types of bioceramic powders into human periodontal defects, the best bone formation was observed with microsized HA, which gave rise to well-differentiated bone nodules at 6 months.148 The mean diameter of the HA crystals was significantly lower than that of the other ceramics tested, approaching that of bone mineral. It was concluded from this ultrastructural study that bioceramics may promote bone formation when implanted into intrabony periodontal defects. Histologic analysis of seven vertical lesions in three adults with severe periodontitis treated with porous HA (Interpore 200) and placement of Gore-Tex membranes showed an increase in bone mass resulting from osteogenesis within the surrounding HA particles, which often fused with osseous seams of the crater.r4’ Polypeptide growth factors are a class of potent natural biologic mediators that regulate many of the activities of wound healing including cell proliferation, migration, and metabolism. Platelet-derived growth factor (PDGF) and insulinlike growth factor-l (IGF-1) have been shown to regulate DNA and protein synthesis in bone cells in vitro and to interact synergistically to enhance soft tissue wound healing in vivo. A study investigated the effect of the combination of PDGF and IGF-1 on the regeneration of both the soft tissue and hard tissue components of the peri-

JULY

1992

VOLUME

68

NUMBER

1

COMMITTEE

REPORT

odontium following conventional periodontal surgery in 13 beagle dogs with naturally occurring periodontal disease.150 Analysis of biopsies obtained at 2 and 5 weeks after surgery revealed a fivefold to tenfold increase in new bone and cementum in PDGF/IGF-1 treated sites at both time points compared with controls. This study demonstrated that the short-term application of the combination of PDGF and IGF-1 may significantly enhance the formation of the periodontal attachment apparatus during the early phases of wound healing after periodontal surgery. Autotransplantation of third molars to replace molars with advanced periodontal disease was shown to be successful in 15 of 18 sites over an 18- to 72-month period.i51 After extraction of the diseased molar, autotransplantation of a third molar was immediately performed. Occlusion was checked and the transplant was splinted to adjacent teeth for 2 to 3 weeks, after which the splint was removed and endodontic treatment was performed. The low frequency of failure due to root resorption was attributed to use of fully erupted third molars. In an evaluation of the degree of root coverage obtained by five periodontists using the free gingival graft technique with CA root demineralization, 103 sites in 58 patients were observed 12 months after surgery.152 Overall, complete root coverage was achieved 72.8% of the time and mean root coverage was 87.6 % . The results of this study indicate that coverage of exposed root surfaces can be achieved with a high degree of predictability in selected cases. Scanning electron microscopic evaluation of the epithelium over free gingival grafts and connective tissue grafts, used for gingival augmentation, at 30 days after operation indicated that there was a more rapid, less traumatic healing and maturation of the connective tissue graft.153 Artificially created gingival recession in dogs was treated with nonresorbable barrier membranes and a fibrin-fibronectin seaLIS Results of this study indicated that this technique favored the gain of connective tissue attachment in rootcoverage procedures.

periodontal disease in a small number of especially diseasesusceptible individuals. In a 30-month prospective study, 98 adults previously treated for moderate to advanced periodontitis and on a trimonthly recall schedule were screened for the presence of critical levels of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, and Preuotella intermedia.156 With the exception of P. gingivalis, for which insufficient data were available, the results indicated that the presence or absence of the other two periodontopathogens cannot by themselves serve as a reliable predictor of future episodes of recurrent disease in a population of treated patients on a regular recall schedule. Among the clinical measurements, the only consistent and significant observation concerned the probing depth measurement. These results confirm previous reports that patients with deep pockets may be at greater risk of recurrent of disease and support the similar findings in patients evaluated at the completion of nonsurgical therapy. Current microbiological testing procedures have value in planning antibiotic therapy, but should not be considered alone as prognosticators of future disease activity. Results seen in 30 previously treated periodontal patients, evaluated in a crossover study, indicated that the interdental brush used in combination with a toothbrush is more effective in the removal of plaque from interproximal tooth surfaces than dental floss used in combination with a toothbrush.157 All new patients beginning periodontal maintenance therapy after active periodontal therapy in a specialist periodontal practice were evaluated on the basis of compliance with the maintenance schedule 3 to 6 years after surgery. 158 Only 36 % were found to be in compliance, with the greatest patient loss in the first year. The most common reason given for noncompliance was that a general practitioner was attending to the patient’s periodontal treatment needs. Many considered periodontal maintenance therapy too expensive, and a significant proportion considered that they no longer required treatment.

Periodantal

Periodontal, restorative, and interdisciplinary considerations

maintenance

therapy

Successful control of dental diseases affecting the periodontal structures as well as the teeth is acknowledged to be dependent on continual preventive care following active therapy. The effectiveness of consistently monitored care and the recognition of recurrence of disease continue to be studied in patients in maintenance programs. An evaluation of 317 subjects who completed a 15-year preventive maintenance program indicated that improved self-performed oral hygiene, daily use of fluoridated dentifrice, and regularly repeated professional tooth cleaning effectively prevented recurrence of dental caries and periodontal disease.155 It was observed that some subjects and sites displayed signs of recurrent caries and periodontal disease. It should be realized, therefore, that plaque control measures and topical fluoride use, along with regular professional care, may not be adequate to preclude caries and

THE

JOURNAL

OF PROSTHETIC

DENTISTRY

It has been reported that approximately a third of teeth treated by root resection fail after 10 years. In a study of 70 root resected teeth in 62 patients, approximately one third were considered faulty because of the presence of subgingival residual roots, furcal lips, and ledges.15g This high prevalence of faulty root resections should alert the prosthodontist to intercept these residual defects before the completion of permanent restoration. A failure rate of only 5.7% was reported for multirooted teeth subjected to root resection treatment and evaluated clinically and radiographically for 3 to 11 years.160 This low failure rate was attributed to applying this technique with the proper indicators in an optimal oral hygiene environment with precise restorative technique. A study concluded that, with careful patient select,ion

153

JENDRESEN

and good oral hygiene, hypermobile, periodontally compromised abutment teeth can support a unilateral fixed partial denture (FPD) for up to 2 years.161 It was recommended that such teeth be considered to support FPDs under the following conditions: (1) where there is lack of other favorably distributed abutment teeth with greater levels of periodontal support; (2) for a carefully selected patient with advanced loss of periodontal support who requires tooth replacement and desires to retain the existing dentition; (3) when the patient and the dentist are committed to a fastidious plaque control and maintenance program; (4) when there is a recognition of the guarded prognosis associated with an FPD supported by periodontally compromised teeth. With all the factors considered, the use of periodontally compromised abutment teeth to support a unilateral FPD for a highly motivated patient may be the best treatment alternative. In an analysis of 831 patients receiving regular preventive dental care in private practices, subgingival margins of cast restorations were associated with increased gingival inflammation when compared to like, nonrestored teeth.162 The degree and extent of marginal inflammation associated with subgingival restorative margins was reported to be influenced by four factors: (1) failure to maintain proper emergence profile; (2) inability to adequately finish and/or close subgingival margins; (3) placement of subgingival margins in an area with minimal to no attached gingiva; and (4) violation of the biologic width.163 Attention to these factors should help reduce the adverse impact of restorative margins that must be placed subgingivally. Of interest, the amount of plaque and the degree of gingivitis adjacent to composite fillings were not significantly higher than those for glass ionomer cement and enamel surfaces in both a cross-sectional and an experimental gingivitis study in 16 adults.164 A problem associated with performing crown-lengthening procedures before root canal therapy is that there is a delay of at least 3 to 4 weeks after surgery for healing before clamp placement for isolation. This delay may not be feasible for a patient with endodontic pain requiring immediate treatment. In a case report, a tooth with subcrestal caries and pulpal involvement was treated in a combined procedure of flap surgery with bone reduction 3 mm apical to the carious lesion, root canal treatment, and placement of an amalcore restoration in one appointment of approximately 2 hours duration.165 An attempt was made to analyze the process of supereruption following loss of an antagonist tooth.l@ Unfortunately, there was improper use of the terms “active eruption” and “passive eruption” and an introduction of an unsupported phenomenon in which it was suggested that growth of periodontal tissues including alveolar bone are responsible for “carrying” a tooth occlusally. This combination of improper terminology and physiologic concepts among other limitations renders interpretation of findings in this report impossible.

154

ET AL

Maxillary anterior fixed prostheses may be compromised when pontics are adapted to deficient residual alveolar ridges. A study evaluated the effects of ridge contour on esthetics and function by means of a structured interview with 30 patients to determine causes of satisfaction or dissatisfaction.167 Results showed that patients with buccolingual ridge deficiencies (type I) had a higher subjective level satisfaction with their prostheses than did those with apicocoronal (type II) or combination ridge deficiencies (type III). These results suggest that consideration be given to ridge augmentation procedures before construction of anterior fixed prostheses, especially in type II and III deficiencies. Porous HA blocks were implanted in sites of maxillary anterior ridge deficiencies to improve the pontic/ ridge relationship for a fixed prosthesis in two patients.168 At 2% to 3 years after surgery, the ridge contours were maintained and continued presence of the implants was confirmed radiographically. It was suggested that care be taken to avoid overfill with block material to prevent potential sloughing. One of the stated disadvantages of this augmentation procedure is that the flap limits the amount of material that can be placed, resulting in less than optimal esthetics. The use of a Subperiosteal tissue expander (Cox-Uphoff International, Santa Barbara, Calif) was described to address the problem of insufficient soft tissue to cover extensive amounts of graft or implant material necessary to achieve proper contour.16g The tissue expansion technique reportedly generates sufficient tissue in 2 to 3 weeks for coverage of large blocks of donor material without tension on the surgical flaps.

CRANIOMANDIBULAR DYSFUNCTION Anatomy, physiology,

FUNCTION

AND

and pathophysiology

Several articles were published on the results from investigations of animal and human autopsy materials. Two publications described the biomechanical properties and collagen fiber orientation of temporomandibular joint (TMJ) disks in dogs. The first study emphasized the gross anatomy and collagen fiber orientation of TMJ disks in nine healthy dogs (Canis familiaris) using macroscopic, stereomicroscopic, light microscopic, and scanning electron microscopic techniques.170 The surface of the disk showed an undulated configuration. The authors described it as a “finger print pattern” under stereomicroscope. It appeared to aid in storing synovial fluid and providing lubrication to the joint. The fine fibrils in the middle part of the disk are twisted together tightly. They form in their anteroposterior direction a shock absorber. The mediolatera1 fibers are composed of loose bundles. They are crossed perpendicularly by anteroposterior fibers in anterior and posterior bands. The periphery of the disk resembles a fibrous annulus composed of the mediolateral fibers of anterior and posterior bands and the anteroposterior fibers of the medial and lateral portions of the middle band. The fibrous annulus is suggested to have a stabilizing function.

JULY

1992

VOLUME

68

NUMBER

1

COMMITTEE

REPORT

The second study encompassed eight disk specimens.171 They were inserted in a soft tissue uniaxial tensile and stress-relaxation test machine and immersed in a bath of Ringer’s solution at room temperature. Uniaxial tension was applied to the specimens. Simultaneous recordings were performed by an X-Y recorder. Three conclusions were drawn from the study: (1) The transverse tensile stiffness, strength, and equilibrium moduli of anterior and posterior bands of the disks were almost equal. They were greater than those of the middle part. (2) The physiologic strain region of the TMJ disk was approximately 4 %. (3) Because the permeability of the TMJ disk is lower than that of hyaline cartilage, it probably plays a special role in TMJ disk function. Although the results were obtained through animal experiments, the resemblance of “finger print pattern” are interesting. The findings indicate the objective rationale for individual designs and variation in treatment approach to TMJ diseases. One study on the peripheral distribution of trigeminal nerve fibers in rat TMJ studied by an anterograde axonal transport method with wheat germ agglutinin-horseradish peroxidase also underlined the difference between the different parts of the TMJ disk. 172Horseradish-peroxidaselabelled nerve fibers were found in the anterior and posterior bands of the articular disk. They terminated as nerve endings near the intermediate zone of the disk, in which no nerve endings were seen. In addition other nerve fibers penetrated from deeper layers into the synovial membrane. They terminated as nerve endings close to the articular cavity. In another study the binding of wheat germ agglutinin to rat mandibular condylar cartilage was investigated.173 Two distinct patterns of binding in the pericellular matrix were found. One showed binding without apparent contour. The other binding was confined to the matrix but with conspicuous condensation forming a pericellular rim. As the binding sites denote sugar specificity of a certain lectin, the binding may be linked to structural changes or modifications of proteoglycans in the phase of preparation for endochondral calcification. The effect of occlusal bite raising splints on electromyogram (EMG), motor unit histochemistry, and myoneuronal dimensions in rats was investigated in 21 male adult Sabra rats.174 EMG activity showed great variability immediately after splint fabrication. However, the overall interpretation of the results was that after approximately 1 week the initial reductions of EMG activity were gradually approaching baseline levels. The three main types of muscle fiber did not change after bite-raising splint application. The results indicated that splint treatment in rats initially reduces EMG activity while the muscle-type characteristics remain stable. The effect of lower activity on the motor end plates suggested that the neuromuscular junctions are quite sensitive to functional changes. In two articles by the same author, the posterior attach-

THE

JOURNAL

OF

PROSTHETIC

DENTISTRY

ment of the human TMJ disk was described in detai1.175,176 The posterior attachment was examined in 21 disk-posterior attachment specimens that fulfilled the following criteria for selection: (1) The articular tissues of the temporal and condylar components were not associated with any signs of pathosis. (2) The posterior band of the disk was situated above or only slightly anterior to the summit of the condyle in all regions of the joint. (3) The disk was biconcave in sections cut through the central and mediocentral regions and biconcave or rectilinear in profile in the laterocentral region; and (4) the disk showed no signs of fissuring, fraying, or perforation. Histological sections of 20 pm and 30 pm thickness from nine joints were evaluated. The additional 12 joints were evaluated from sections with the thickness of 15 to 20 pm. Twenty-six arthrograms from 19 healthy subjects were also separately analyzed and included in the descriptions of the disk attachment behavior. The extensive verbal descriptions were completed by clear and beautiful histologic slides allowing an accurate description and interpretation. The results of the studies are summarized with the posterior attachment of the TMJ disk showing a highly compliant tissue that is capable of large volumetric fluctuations. It seems that the posterior attachment of the disk appears to function as the device for rearrangement of blood, tissue fluid, and synovial fluid. An extensive literature review completes the author’s own observations. Bite force magnitude and moment were analyzed threedimensionally.177 In a study involving seven human subjects, the effect of the three-dimensional orientation of occlusal force on maximal bite force magnitude was examined at three different unilateral anteroposterior bite positions. The results, based upon 17 precisely defined directions from each position, using a three-component force transducer and visual feedback, showed that the largest possible bite force was not always produced in a direction perpendicular to the occlusal plane. Maximal bite force in medial and posterior directions was larger than the bite force in lateral and anterior directions. The produced bite force was larger at the posterior bite point than at the anterior bite point. The combined movement produced by the jaw muscles was largest for vertical bites and smallest for posteriorly directed bites. The inherent weaknesses in electromyographic recording techniques are mentioned as plausible reasons that the limits of motor-unit territory in the masseter muscle may have been underestimated.178 Therefore the conduct of the study involved single motor-unit responses recorded as time-locked events from 32 paired-needle recording sites throughout the masseter muscle of three subjects. Recording sites were located stereotactically with an optical system, magnetic resonance imaging, a common reference, and then displayed graphically in three dimensions. The mean linear separation of the paired recording sites was 8.8 + 3.4 mm. The putative territories had a preferred orientation in the antero-posterior axis. Motor-unit territories were larger 155

JENDRESEN

than described previously and appeared to be related to anatomic compartments. The restriction of these territories to discrete regions of the muscle provides an anatomic substrate for selective regional motor control of the human masseter muscle. Nine healthy dental students participated in a study on the precision of motor control in human jaw and limb muscles during isometric contraction in the presence of visual feedback.17g The students were asked to react to the target force trajectory as quickly and accurately as possible. The signal, which was produced by a function generator, was presented as a step wave with a variable duration of approximately 3 seconds. The chosen amplitude corresponded to a force level approximately 15 % to 20 % of the individually determined maximal voluntary contraction. Four different muscle groups were tested in four different functions: (1) cutting, (2) jaw clenching, (3) pinching, and (4) plantar extension. The results indicated that the human capacity to maintain a particular isometric force in the presence of visual feedback during a force-level, pursuittracking experiment is less developed for the jaw-closing muscles than for the limb muscles. The authors suggested that the projection on the trigeminal motor neuron pool from visual inputs is poor or that the trigeminal effector system itself is less finely timed.

Epidemiology During 1991 few epidemiology studies were conducted. One hundred nineteen 20-year-olds participated in a 5-year longitudinal study of signs and symptoms of craniomandibular disorders.lsO Each clinical examination was concluded with an index of dysfunction, type of interferences, the degree of dental wear, and an estimated need for treatment. Statistical analyses were not performed. The authors summarized the findings by saying that both signs and symptoms of mandibular dysfunction were fairly common, but in most cases were mild. Twenty-seven percent of the sample were estimated to be in need of some functional treatment. However, the treatment advocated was simple and not time-consuming. Only 3 % of the sample demanded some functional treatment. The material was divided into two subgroups, those judged not to be in need of functional treatment (n = 87, “no-treatment” group) and those judged to be in need of treatment (n = 32, “treatment” group). Although occlusal factors such as interferences were found in higher prevalences in the treatment group, the authors maintain a reluctant opinion toward dental treatment. At the same time they find that the general dentist can handle the problems. The discussion is therefore confusing because of its contradictory messages and difficult to understand. The prevalence of craniomandibular disorders in completely edentulous denture-wearing subjects was investigated in 201 patients. lsl Analysis of data obtained from the dental history and anamnestic and clinical examinations showed that parafunctional habits were prevalent among 156

ET AL

complete denture wearers. Elderly complete denture wearers potentially present more signs and symptoms of craniomandibular disorders than do younger subjects even in the absence of organic problems related to the masticatory apparatus. In a second article on the same material, the statistical analysis showed that the only reliable indicator of craniomandibular disorder was the patient’s sex; that is, the women tended to show more symptoms of craniomandibular disorders than the men.182 The subjects with a history of fewer sets of complete dentures worn appeared to be correlated with an increase in the number of signs and symptoms of craniomandibular disorders. Although the correlation showed a weak predictive power, it was significant enough to indicate that such a relationship could exist in the general population. Although the material was limited and not standardized, the results from a cross-sectional study of 30 patients with craniomandibular disorders (CMD) and 30 controls regarding general musculoskeletal complaints was interesting.rs3 A questionnaire was used to map the locations of pain. In addition “pain tolerance” was measured with cutaneous electrical stimulation over the masseter areas. The CMD patients had a significantly higher number of painful sites on the body than the control subjects. They also showed significantly increased “relative risks” of having musculoskeletal pain especially in the upper region of the neck, the shoulder and lower region of the neck, the shoulder joint, and the thoracic region of the back. Discomfort and pain rating values for the neck and shoulders were significantly higher for CMD patients than for controls. The measurements of pain tolerance did not differ between groups. However, an individual variation was found among the CMD patients. Those who had pain in many different parts of the body were the least tolerant of experimentally induced pain.

Diagnostics Many articles dealt with diagnostics of craniomandibular dysfunction. Most of the publications fell into one of two categories, instrumental or clinical.

Instrumental The errors of instrumental diagnostics, that is, the error of the instrument and/or error in interpretation are the background of an error analysis of a magnetic jaw-tracking device.ls4 The study focused on the calibration of a new generation of hardware for tracking jaw position “Bio EGN,” a modification of the Sirognathograph instrument (Seimens Corp., Benshein, Germany). The calibrated area included such dimensions that it ensured the incorporation of the maximal possible mandibular mobility. The authors concluded that linear analysis of chewing movements was reasonably adequate without major distortion, because the mandibular movements were limited. However, linear analysis of maximal mandibular movements should be viewed with caution.

JULY

1992

VOLUME

68

NUMBER

1

COMMITTEE

REPORT

In another study a technique was developed to measure, analyze, and describe the full three-dimensional kinematic characteristics of the TMJ during any mandibular activity.‘- The technique was based on determination of the relative position between the mandible and the temporal bone from measurement of the location of points on lightweight frames rigidly attached through splints to the maxillary and mandibular teeth. An optoelectric kinematic data acquisition system was used to record the location of the points. As the study did not provide a comprehensive investigation of the kinematic characteristics of the TMJ it should be looked upon as a demonstration of a technique. Not until the three-dimensional kinematic characteristics of normal and dysfunctional human temporomandibular joints have been tested and objectively evaluated will the diagnostic value of the technique be known. An algometer (pressure threshold meter, PTM) connected to a stop watch was used to study the relationship between the rate of pressure applied over the masseter muscle and the pressure pain threshold in 20 consecutive patients with various degrees of craniomandibular dysfunction.ls6 The pressure pain threshold values were dependent on pressure rates and independent of the method used. The pressure rate should be kept within the range of 0.50 kg/cm2/second to obtain an acceptable reproducibility. Repeated recordings of the same site with a constant pressure rate did not influence the PTM value significantly. It was mentioned by the authors that it is important to familiarize the patient with the PTM to obtain reliable feedback and that the PTM value is dependent on the patient’s subjective experience and verbal response to the pressure pain threshold. The resemblance between the technique used and the established clinical palpation is noticeable. Therefore the results indirectly also advise the clinician to maintain a constant pressure at clinical palpation, when applied, if the patient’s response shall be accounted for. A critical literature review is the base for the introduction and the discussion in an excellent study of the evaluation of the relationship between TMJ sounds and craniomandibular movements.ls7 Fifty-six subjects participated in the study. Mandibular movements in 28 subjects with TMJ sounds were evaluated and compared with those of 28 control subjects with no signs or symptoms of TM disorders (including the absence of clinically detectable TMJ sounds). The 28 subjects with TMJ sounds were otherwise without any signs or symptoms. The mandibular movements were recorded with a Sirognathograph instrument interfaced with a personal computer. The TMJ sounds were recorded with contact microphones. The only statistically significant difference in the variables tested found between the two groups of subjects was for the mean mandibular deviation in the frontal plane. It was greater in the test group, 3.2 mm versus 2.2 mm in the control group. All combinations of mandibular movements were found to occur in relation to joint sounds with no obvious pattern. There was

THE

SOURNAL

OF

PROSTHETIC

DENTISTRY

a large variability in both the study and control subjects. Joint sounds were also frequent in the persons with no other signs or symptoms. Therefore the results indicated that caution should be exercised in interpreting the characteristics of electronically recorded mandibular movements and TMJ sounds. Opening and closing movements were recorded in nine patients by means of an opto-electronic motion recorder before anaesthesia, after anaesthesia, and after arthrography.is8 The system computed the trajectories of a condylar point in the sagittal, frontal, and horizontal planes. Data were analyzed for changes in the position of the clicks, for the amount of condylar translation, and for changes of the trajectories between recording conditions. The results indicated that arthrography had a significant effect on the position of the opening clicks in all nine patients. After injection, the clicks occurred on average 1.6 mm later than before injection. Arthrography altered the joint biomechanics, but not sufficiently to invalidate the arthrographic diagnosis, because the other parameters examined (maximum anterior condylar displacement, maximum caudal condylar displacement, maximum lateral condylar deflection, and the duration of the open/close cycle) were not affected by the joint anesthesia and the arthrographic procedure. In a study of 41 patients with 40 students as a control group, signs and symptoms with and without temporomandibular disorders were investigated.lsg Four factors were found to be statistically significant between the two populations studied: headache frequency, masticatory muscle tenderness, cervical muscle tenderness, and maximum opening. Only masticatory muscle tenderness was highly sensitive and specific. Maximum opening and cervical muscle tenderness presented very high specificity but low sensitivity. As both restriction in maximum opening and cervical muscle tenderness did not seem to be highly predictive of temporomandibular dysfunction, the results are confusingly interesting. They are in contradiction with other studies. The contradiction underlines the importance that studies based on signs and symptoms need to be replaced by studies based on differential diagnoses. Seventy subjects with the median age of 11.9 years and the diagnosis of juvenile chronic arthritis (JCA) were examined for clinical and radiographical involvement of the temporomandibular joints.lgO The high prevalence of radiographic signs of TMJ disorder was remarkable (48 % ); however, it was not discussed in detail by the authors. It may be ascribed to the lack of knowledge of the radiographic outline of the normally growing joint, because the major portion of the subjects had monopauciarticular involvement of the disease. Subjective symptoms were more prevalent among the older subjects. The critical remarks made by the authors are worth repeating, to improve design and interpretation of similar studies. “The study had the same basic limitations as other cross-sectional studies on TMJ involvement 157

JENDRESEN

in JCA. It is not possible by such studies to describe the development of the TMJ involvement in relation to the onset of the general disease, as the disease course fluctuates. In some patients, the joint symptoms are more or less chronic, in other patients periods of inflammatory activity are followed by silent periods and in some patients signs and symptoms of joint disease will be absent for long periods, perhaps for ever. Longitudinal studies are thus necessary in order to learn the pathogenesis of the TMJ involvement in JCA and to find guidelines for clinicians.“lgO An article, much too limited in scope, described diagnostic tests used in determining the role of the occlusion in temporomandibular joint disorders.igl Positive tenderness to palpation of the inferior bellies of the lateral pterygoid muscles and a positive stress test were the basis. The article stressed an interesting concept for clinical distinction of treatment. However, the objective separation of etiological factors that were assessed was lacking. Another study drew attention to an area described as being neglected in diagnostics: the hyoid bone syndrome.ig2 One case was described and thoroughly examined. The injury involves the origin fibers of the middle pharyngeal constrictor muscle on the greater cornu of the hyoid bone. More investigations are necessary to direct its treatment. Compared with healthy men and women, patients with temporomandibular disorder reported more numerous and/or frequent somatic, psychologic, and behavioral symptoms of stress.lg3 The average temporomandibular disorder patient is in general more disease-oriented. The results definitively indicate the importance of considering biopsychological modalities as well as diagnostics in treatment, and a psychosocial assessment should be used before pure occlusal therapy gets priority. It is therefore interesting and promising to realize that a model for dentists to evaluate the accuracy of diagnostic tests for temporomandibuiar disorders as applied to a TMJ scale was described in one article.ig4 One literature review article on the multidisciplinary approach to the differential diagnosis of facial, head, and neck pain summarized what several of the previously mentioned articles also mentioned.lg5 If no evidence of dysfunction in mandibular movement, masticatory muscles, or dentition can be found, treatment should not be instituted and prompt referral should be made for diagnosis and treatment. Different forms of headaches, nasal and sinus pain, ocular pain, neuralgias, otalgia and otologic symptoms, dizziness and vertigo, throat symptoms, and cervical pain are all conditions that demand a multidisciplinary approach with or without the combination of craniomandibular disorders. Additiona!

diagnostic

tests

A methodological review article on the research on temporomandibular joint clicking is a summary article from

158

ET AL

last year that incorporated studies conducted along the same lines.ig6 However, it is good that a critical view is expressed regarding the way the dental profession has looked at TMJ sounds. Hopefully this article will be the last one to discuss clicking alone. Hopefully it will also serve as a trigger for objective and multivariate analysis whenever the sign of clicking is to be addressed. The article underlines the concept of ignoring TMJ clicking when present without pain or discomfort. Clicking alone is no indication for treatment. In testing personality hardiness, one study dealt with 75 patients and 89 control subjects. The preliminary results indicated that hardiness offers a unique way of looking at interrelationships. lg7 It addresses the potential vulnerability of the psycho-physiologic system under various life conditions. The results are promising as the fluctuations of craniomandibular dysfunction are so often the common problems in clinical diagnostics. In a comparative study between trancranial radiography and linear tomography, a sonic digitizer was used to measure joint-space dimensions. lg8The corrected and standard transcranial projections did not accurately reproduce the anatomic joint spaces or the relative condylar positions. Only the corrected tomographic projection accurately reflected the condyle-fossa relationships. Although the study only involved six human skull specimens, the results underline many previous conclusions that tomography is superior and that the interpretation of condylar position should be made with utmost caution. Ten dental students participated in a study on the reproducibility of occlusal contacts utilizing a computerized instrument (T-scan, Tekscan Inc., Boston, Mass.).lgg The results showed 100 2%accuracy and reproducibility for all contacts in all subjects. When the conventional registration with the silk ribbon method was used, the tested contacts were also reproduced at the same location evenly and simultaneously. The actual difference between the two techniques presented does not seem to be more than the documentary value of the T-scan registration. Sagittal condylar guidance as determined by protrusion records and wear facets of teeth was examined in 45 healthy and dentulous subjects. 2ooCasts were mounted in a semiadjustable articulator. Protrusion wax interocclusal record and matching the wear facets of opposing canines and contralateral molars were the two modes of registration. Significant differences between the mean angles of the two methods were found, thus an alarming signal that at least one method is wrong. Further studies are needed to support the validity of these steps of instrumental analysis. The results from one study on the validity and predictive value of four assessment instruments for evaluation of the cervical and stomatognathic systems are promising.“i A IO-item cervical pain questionnaire, a lo-item TMJ pain questionnaire, the cervical range of motion (CROM) instrument, and the Craniomandibular Index were used in 25

JULY

1992

VOLUME

68

NUMBER

1

COMMITTEE

REPORT

patients referred for physical therapy due to hyperextension-hypertlexion injuries. However, a clean-cut clinical interpretation as an applicable conclusion is lacking. When symptom characteristics in 100 TMD patients reporting blunt trauma and/or whiplash injury were investigated, the different types of trauma produced significantly different functional limitations and pain sites.202 With the spectrum of different events, one can not avoid questioning the possible validity of so frequently used indices in many studies. One study was performed on 61 male dental students using a tracking device to investigate normal movements of mandible at the mandibular incisor.203 The range of mandibular movements was measured in frontal, sagittal, and horizontal planes. The results did not differ from previous measurements with other techniques. However, it is important to repeat the following conclusion by the authors. As maximal incisal opening is the measurement used most often to determine functional mandibular movement all mandibular movements need to be considered in order to improve diagnosis and more accurate monitoring of change during the treatment of craniomandibular disorders. Occlusion In the area of occlusion, the articles dealt with more confusion than conclusions. Two excellent literature reviews deemphasized the relationships between occlusion and temporomandibular disorders.204, 205Although the reports aimed to be objective, the reader cannot avoid questioning several of the conclusions. General statements were based on the results from too many different clinical materials with probably a lack of differential diagnoses. Much emphasis was placed on the diagnosis of disk displacement. The definitive strength of the two articles is that they can stimulate to alter the position of occlusion in present research. Occlusion may still play an important role when analyzed and focused in a specific problem (differential diagnosis) . Against this background, some other articles make interesting reading. 206-208When the results of 264 19-yearold adolescents were reexamined after 2 years, the number of contacting teet.h in the intercuspal position during light pressure was the occlusal factor with the most significant relationships to symptoms of mandibular dysfunction. Being tense and having few contacting teeth seemed to potentiate the risk of symptoms.206 The other studies dealt with signs and symptoms of mandibular dysfunction after &year follow-ups.207, 208Subjects with restored dentitions had a higher degree and frequency of mandibular dysfunction than the subjects with intact teeth. The subjects who had restorations during the follow-up period also showed a trend to the development of signs of mandibular dysfunction. In conclusion the authors stated that dental filling therapy is of greater etiologic importance in mandibular dysfunction than had been thought previously.207, 208 The results are interesting in

THE

JOURNAL

OF

PROSTHETIC

DENTISTRY

that the historically multifactorial etiology starts to deteriorate. The attempt to combine certain factors is welcome and the results are promising for the successful treatment by a team approach. The results from a small clinical study of tooth contact patterns in seven patients confirm the results of the previously mentioned follow-up studies, when compared with 7 normal subjects. 2ogThe tooth contact patterns were examined by a newly devised radiotelemetry system. Contacts were measured under resting, working, and swallowing conditions. The patients seemed to have higher values for total number and time of tooth contacts. The results suggest that patients with temporomandibular dysfunction exhibit increased tonus of jaw-closing muscles, which is probably caused by occlusal disharmonies and psychological stress. Seventy-two migraine sufferers were compared with 37 matched control subjects to establish whether signs of mandibular dysfunction, occlusal discrepancies, and known clenching or grinding habits were more frequent among the diagnosed migraine patients. 210Signs of craniomandibular dysfunction and parafunction were more prevalent among the patients. However the occlusal criteria of nonworking side or protrusive interferences and slides of more than 1 mm to the intercuspal position were equally found in the two groups examined. As the amount of dental wear was also found to be equal among the two groups, clenching was suggested to be the most plausible factor as the nocturnal habit causing migraine. There was no link between occlusal factors and migraine. Nocturnal bruxing events in 12 subjects with sleep-disordered breathing and in 12 control subjects were investigated.211Bruxing events were common in both groups. The effects of another oral habit (snuffing) was investigated in one study.212 The results of the 100 participating snuff users indicated that the increased salivary flow with snuff chewing served as a lubricant that protected the dental surface from wear. The results from electromyographic and computer analyses (T-scan) of patients suffering from chronic myofascial pain-dysfunction syndrome before and after treatment with immediate complete anterior guidance development213 may sound attractive to the dentist, but must be evaluated with utmost caution and skepticism. Only seven patients were examined. No controls were used. No attempt was made to retrude the mandible in centric relation and no splints were used before adjustment. Recordings were collected during one month. Not until further studies have been performed and with standardized parameters can the results be considered valid. In an extensive literature review around the relationship of occlusal vertical dimension to the health of the masticatory system, the authors concluded that current scientific knowledge does not support the hypothesis that moderate changes in occlusal vertical dimension are detrimental to

159

JENDRESEN

the masticatory system. 214However, most of the studies, not to say all of the studies referred, dealt with changes of increase of vertical dimension. A general statement on the relationship between occlusal vertical dimension and the health of the masticatory system therefore does not yet exist. Treatment The general trend among the articles on treatment during 1991 was that a special treatment modality was tested on a group of patients with basically the same disease. Therefore, as a reader, one gets the impression of a continuous improvement in the attempt to provide the correct cure. In general the articles did not hazardously mix different treatment modalities as so often was seen in the past. Rather, the reviewed articles were grouped according to the types of diseases treated. A three-dimensional electrognathography of an incisor point was used to detect peripheral correlates to deprogram the jaw elevator muscles. 215Putative deprogramming was attempted through the clinically recommended use of a leaf gauge, placed for 10 to 15 minutes between the maxillary and mandibular anterior teeth and disoccluding the posterior teeth by approximately 2 mm in 13 healthy subjects. The use of the leaf gauge did not affect the displacement patterns of the mandible during voluntary elevation of the mandible from the postural to the intercuspal position. Within a free-way space of approximately 0.2 mm3, the incisor point moved approximately 2 mm vertically, 1 mm sagittally, and 0.2 mm laterally. On the basis of electromyography and electrognathography, the authors concluded that short-term and nonfatiguing use of a leaf gauge cannot alter normal mandibular closure patterns and normal contraction patterns of the jaw muscles. Long-term 24-hour muscle deprogramming was suggested to be added to the usual chairside methods to include special deprogramming techniques during the corrective procedure itself in a literature review.216 Twenty-three patients with two or more signs and symptoms of pain and tenderness in the masticatory muscles and temporomandibular joint, clicking of the TMJ, and deviated or limited opening were selected and given an occlusal splint in intercuspal position.217 The patients were instructed to clench as hard as possible and to maintain this state for 5 seconds with and without the occlusal splint while the integrated electromyography was run on the masseter muscles. Myoelectrical values were reduced with the splint. However, the relative difference remained virtually unchanged. Although the results indicated that the occlusal splint could decrease masseter muscle activity and thus exert a therapeutic effect, the clinical relevance of the tested splint is still not fully interpretable because the splint was made in intercuspal position, which very well might have been the parafunctional position. One study tested 26 patients with mainly a myogenous origin of pain for the short-term effect of a stabilization 160

ET AL

appliance.218 A full maxillary appliance was used 24 hours a day by each patient. The appliance had an intercuspal position in harmony with the retruded mandibular position, with slight impressions of the antagonizing bearing cusps and with anterior teeth incisal edge contacts. The canine was guiding on laterotrusion, preventing mediotrusive contacts. Protrusion was directed through contacts of the anterior teeth only. The patients were instructed to clench at 10 % and 50 % of their maximum clenching effort in the intercuspal position and on the appliance. Recordings were made before and immediately after appliance delivery, and 2 and 4 weeks after delivery. The average EMG activity of the masseter muscles remained the same during the period of appliance use, whereas the anterior temporal muscles showed an immediate and long-lasting reduction in activity. The appliance also resulted in an improvement in the balance of left and right masseter muscle activity. Bipolar surface electrodes of silver amalgam were used. Stretch-based relaxation and the reduction of EMG activity was tested and evaluated in 34 patients with elevated masseter activity.21g The patients were randomly assigned to either a postural relaxation/rest experimental group or a stretch-based relaxation experimental group. Following a psychosocial stressor and application of the relaxation procedure, persons in the stretch-based group showed greater reductions in EMG activity than did those in the postural group for the right masseter region (p < 0.04) and the left masseter region @ < 0.03). The results are promising in their possibility to actively direct the modalities used in physical therapy for masticatory muscle pain. In two studies the effects of medication on bruxism were tested.220,221In one of the studies portable EMG recorders were used to monitor unilateral masseter muscle activity during sleep in eight patients identified as nocturnal bruxists.220 Following an initial baseline period the patients were given, in a randomized double-blind study, either tryptophan (50mglkg of body weight) or a placebo for 8 days followed by an additional 8 days of reverse medication. L-tryptophan is a precursor of the neurotransmitter, serotonin. Dietary patterns and food intake were monitored throughout the experimental period. No significant treatment differences in bruxing levels were found. The results were concluded with the direct advice that recent research failed to show that tryptophan and diet had a positive effect on chronic myofascial pain associated with bruxism and suggested that further studies with tryptophan would not be fruitful. The U.S. Food and Drug Administration (FDA) has banned the over-the-counter sale of tryptophan until further notice. In the other study on medication, 20 patients were enrolled.221 However, the clinical material encompassed several diagnoses. Thus the experimental group was not as homogenous as one would wish to see. A double-blind study was undertaken to test the administration of low doses of the long-acting benzodiazepine drug clonazepam in the

JULY

1992

VOLUME

68

NUMBER

1

COMMITTEE

REPORT

management of chronic intractable temporomandibular disorder with myofascial pain in patients who were not responsive to occlusal splint, behavioral therapy, and physical therapy. Clonazepam is described having cholinergic, “GABA-ergic,” serotonergic, anxiolytic, muscle relaxant, and sedative properties. The investigators found clonazepam effective when compared with a placebo. However, with the potential side effects such as depression and liver dysfunction, as mentioned by the authors, the very few and weak significant differences between the two groups tested do not justify the use of clonazepam in the routine practice of CMD treatment. Further studies are absolutely necessary before the general dentist should even consider it as a treatment modality. Two studies investigated the effect of intra-articular injections of glucocorticosteroids into the temporomandibuiar joint.222z223 The one study involved 16 patients with signs of TMJ arthritis.222 A mixture of 0.5 ml of betamethasone was used in a suspension of 6 mg/ml (Celestone bifas, Schering Corp.) and an equal volume of lidocaine (Xyiocain, Astro Pharmaceuticals, Inc.) 10 mg/ml were injected into the superior joint compartment of the TMJ three times with an interval of 1 week between treatments. The effects were evaluated before, 2 years after, and 8 years after treatment. The results reported a significant reduction of subjective symptoms and clinical signs at the follow-up examination. Remineralization of initial bone erosions occurred during the years of treatment. The results indicated that the long-term prognosis of intra-artitular glucocorticosteriod injections for TMJ arthritis is good and that there are no radiographically demonstrable side effects of the treatment. However, the criteria for evaluation must be questioned. The radiographic photos presented seem to be taken with different angles of projection. Because the patients had been treated with other modalities, one cannot exclude the possible effects of such treatments skewing the effects studied. The other study dealt with the short,-term effect of intra-articular injections of sodium hyaluronate, glucocorticoid, and saline in three groups of 41 patients with rheumatoid arthritis of the temporomandibular joint. 223 The patients were randomly chosen for the injection applied and 0.7 ml of the allocated drug was injected twice, 2 weeks apart. The subjective evaluation of the treatment rendered was favorable for sodium hyaluronate and glucocorticoid. Mouth-opening capacity was increased mostly by glucocorticoid. Sodium hyaluronate had an intermediate effect and saline had almost none. Although the results may have been influenced by placebo, they are interesting in their proportions of success between the three different types of injected material. Long-term effects are welcome before a general application of injections in rheumatoid temporomandibular joints are justified. A surgical but functional approach to the treatment of temporomandibular joint internal derangement was described in one article.224 Clinical experience from 237 pa-

THE

JOURNAL

OF PROSTHETIC

DENTISTRY

tients with arthroscopic surgery and the effect of arthroscopic lysis and lavage of adhesions in the superior joint compartment on disc position and mobility in 92 patients were the background with a recent literature review for the proposed functional approach. The authors stated that a review of the multifactorial theories of etiology of pain in the articulating structures supports the philosophy that normalization of function instead of normalization of anatomy, is the key to treatment of internal joint derangement. The mobilization of the adhered disk and release of capsular restraints instead of anatomic reduction decrease load concentration and allow pain-free function through physiologic adaptation. The surgical procedure allows an increased function of the condyle/disk complex against the temporal component. The position of the disk in front of the condyle does not change in the majority of patients treated. The authors of an article on the improvement in myofascial pain and headaches after TMJ surgery positioned surgery as an alternative when previous modalities had failed.225 The purpose of the study was to investigate the effects of surgical treatment on patient reports of TMJ pain, joint clicking, facial muscle pain, neck and shoulder pain, and headache. However, as differential diagnoses were lacking, the procedures were based upon symptoms only and no direct distinction was made between different procedures in the report of treatment. The reduction of myofascial pain and headaches may be ascribed to general decrease in tension due to pain reduction instead of to the surgical procedure itself. A manipulation technique for treatment of anterior disk displacement without reduction was described and tested in 35 patients.226 The basic procedure described by the authors is even self-applicable by the patient. The thumb and forefinger of the one hand are active in directing the mandible while the forefinger and middle finger of the other hand are supporting the gonion of the affected side. Gentle but active laterotrusive and opening movements are performed by the patient. The intralocked disk position seems possible to loosen up, especially in young patients. The technique must probably be practiced and demonstrated before it can be understood. However, it is good to know that all manipulation does not necessarily have to be traumatic. The chewing and swallowing activity of jaw-closing muscles was studied longitudinally in 30 partially edentulous subjects who were provided with an immediate complete upper and a partial lower denture.227 Electromyographic recordings of the anterior temporal and masseter muscles were obtained during habitual chewing of apple and during swallowing of saliva and water before final extractions and at intervals 7 weeks, 6 months, 1 year, and 2 years after denture insertion. The findings of the e-year electromyographic recordings indicate that reestablishment of the posterior occlusion by dentures tends to normalize the chewing activity of the jaw-closing muscles by

161

JENDRESEN

increasing the chewing force. In contrast to the muscle intensity during swallowing, the duration of the swallows appeared to be affected by wearing of the dentures, longer swallows being observed at the 2-year stage. The results underline the importance of regular controls of the dentures to maintain optimal functioning of the masticatory system. Fifty-four human temporomandibular joints were histomorphometrically evaluated in an autopsy study.228 Fourteen joints were removed from dentate subjects, 12 joints from totally edentulous patients who were edentulous for at least 10 years and 28 joints from edentulous patients who had worn complete dentures for at least 20 years. Sagittal serial decalcified sections were studied by light microscopy and submitted to histomorphometry. There were histologically different structures in the three groups examined. The dentate group showed a deep mandibular fossa with well-marked cortical layers of the temporal bones and the condyles. The fibrocartilages were multilayered and the articular disks had biconcave outlines. The group of 28 joints from edentulous patients with complete dentures for at least 20 years showed values similar to those of the dentate group. The joints from the 12 totally edentulous individuals were flat, with thinning of the cortical and spongy bones, The fibrocartilages were thin and not multilayered. The results therefore indicated that complete dentures had a favorable and protective effect on temporomandibular joint structures. The results of the two latter studies support the important role of stable occlusion for the maintenance of a functioning stomatognathic system. Until extended gerodontic studies have been performed and long-term follow up studies are completed, the battle about the importance of occlusion for the function of the stomatognathic system may not come to an end. The clinical studies continue to support the role of occlusion in craniomandibular function. DENTAL

MATERIALS

Amalgam As a result of the 30-year period of intense dental amalgam research, accelerating interest in composites and bonding agents, and recent antiamalgamist challenges, the basic research involving dental amalgam has been limited this past year. Laboratory evaluations were conducted on the corrosion products of high copper dental amalgams that were generated in simulated crevices. The corrosion products included copper chlorides in addition to the tin hydroxychlorides, tin oxides, and copper oxides previously known to occur.22g The clinical relevance of this discovery is not yet known. Creep is one of the mechanical properties with the best correlation to clinical performance for dental amalgam. Twelve amalgams were analyzed for creep versus their microstructural characteristics. The volume percent of the eta-prime phase, the grain size of the gamma-one phase, and other matrix variables showed the strongest correlation to creep.230 162

ET AL

A potential alternative to dental silver amalgam is a gallium alloy. These alloys contain no mercury and are therefore incorrectly referred to as gallium amalgams. Gallium melts at 30° C. A plastic transition stage similar to dental silver amalgam is achieved by mixing liquid gallium alloys (Ga-In-Sn) with solid powders of silver-based alloys (AgPd-Sn-Cu-Zn). A noteworthy review of the properties of 39 such alloys has been reported and demonstrates better strengths for all gallium-based systems.231 The only shortcoming is that gallium must be dissolved in corrosionresistant phases to control the corrosion resistance of the system. A traditional problem for all amalgams, particularly high copper amalgam, is low tensile strength. This makes amalgam prone to brittle fracture, particularly in thin sections. Based on this concern, new 3-D finite element analyses using computer modeling techniques were conducted. The models demonstrated that in MOD cavity preparation designs, the key factors were depth, thickness of interaxial dentin, and width of the isthmus.232 This type of analysis is simple with high-speed computers and permits detailed considerations of cavity preparation and restoration design. Amalgam bonding studies continue to investigate amalgam adhesion to new amalgam, enamel, dentin, and composite. The integrity of composite bonding to amalgam was explored with a new laboratory test.233 Initial results indicated that mechanical roughening of the amalgam surface was productive but that etching the amalgam surface before bonding was not. Composite veneering of amalgams using Prisma Universal bond (CaulkiDentsply, Milford, Del.) or a 4-META based system demonstrated some wetting and adhesion problems.234 Amalgam repairs using amalgam bonding agents were only a third to half the unrepaired strength.235 The most impressive amalgam research reported this year dealt with clinical studies of amalgam failure types and longevity. Because of the continuing amalgam controversy, there is keen interest in assessing the long-term clinical value of dental amalgam restoration. Jokstad and Mjor236 summarized the service life and replacement reasons for 186 class II amalgams in an excellent article concerning a large number of clinical factors. Secondary caries was primarily associated with gingival restoration features and could not be correlated with cavosurface margins or cavity size effects. This is important because most clinicians still judge margin fracture observed on occlusal surfaces as the principal criteria for replacement. Bulk fractures were associated with narrow and deep occlusal features and deep proximal boxes. In a similar study by the same group, it was reported that for class II amalgams, the secondary caries rate was 30% and the bulk fracture rate was 24 % .237These observations are characteristic of low copper amalgams. High copper amalgams tend to show less caries and more bulk fractures. A further study demonstrated that ailure was associated with occlusal cavity depth and margins.238 In another study with JULY

1992

VOLUME

68

NUMBER

1

60MMITTEE

REPORT

124 cusp-covering complex amalgams, a 72 % survival rate was observed after 15 years with no significant difference due to pins or patient age.23g The major reason for replacement of dental amalgam continues to be the judgment of dental caries.240 Analysis of a combination of the information from several general practices using low copper amalgams demonstrated that amalgam replacement reasons were ranked as 23 % for recurrent caries, 29 % for new caries, and 14 % for subrestoration caries. The half-life for these amalgams was 5.25 years. Another study documented amalgam replacement reasons in a student clinic setting over several months.241 Nine hundred sixty-five surfaces of amalgam were removed from 436 teeth with failure criteria of margin breakdown (60%) and caries (26%). Evolving information on high copper dental amalgams demonstrates that the half-life is much greater than originally expected. An outstanding article by Smales et a1.242 indicated g-year survival levels of 96 % ,73 % , and 80 % for Dispersalloy (Johnson & Johnson) Tytin (Kerr, USA, Romulus, Mich.), and Indiloy (Shofu Dental Corp., Menlo Park, Calif.), respectively. Alloy composition, Hg contents, or static creep values were not predictive of high copper amalgam performance. Survival did seem to be operatordependent. From another study over 10 years by the same investigator, there was no significant correlation between marginal deterioration and clinical failure. Fifty percent survival rates were estimated to be 14 years and they could only be accurately predicted by clinical observations after approximately 7 years because there was so little failure during the first few years.243, 244Another clinical evaluation of high copper amalgam showed only a 25 % failure rate at 15.7 years.245 Therefore, one might project the true half-life to be in the 20- to 30-year range. In even a further clinical study, comparison of amalgam to anterior composites, glass ionomer cements, and sealants reported that amalgam was unquestionably the longest lived restorative material. Osborne et a1.246reported similar results for 12 amalgams after 14 years. The overall failure rate was only 12.8%) with high copper amalgams performing very well. A continuing concern has been the clinical effect of polishing amalgam on restoration longevity. A clinical study of 97 paired restorations in molars and premolars for 4 years indicated that there was no difference in marginal fracture or surface staining. 247The evolving inference is that as long as the amalgam surface is smooth initially, there is no special benefit to final polishing. Mercury

controversy

Undoubtedly the major concern relating to dental amalgam during 1991 was the mercury controversy. In December 1990, the “60 Minutes” television program in the United States aired almost a half hour segment that was very favorable to the anti-amalgamist point of view. There was immediate and national concern by patients about the relative safety of dental amalgam. In response to that concern, there were numerous professional position papers, THE

JOURNAL

OF PROSTHETIC

DENTISTRY

editorials, conferences, investigations by governmental agencies, and a significant investment of professional time to counter the anti-amalgamist claims. During the past several years there has been increasing research attention to measure small amounts of mercury released from dental amalgam intraorally. A clinical study of 31 patients receiving new amalgams revealed that although minor, increases in blood mercury could be measured for up to 60 days after the restorative procedure.24s Several laboratory studies have begun to identify the relative effect of other variables on level of mercury released. During pH reductions from 7 to 2.5, a threefold to twelvefold increase in mercury from high copper amalgams was detected.24g Amalgams in contact with gold restorations release some mercury. 250Temperature elevations from 37” to 60” C accelerated mercury releases from 1.5 to 5 times.251 The mercury hazard from amalgams has always been perceived to be greater to dentists than to patients because of the amount of amalgam use in restorative dentistry. In a recent study of restorative treatment of Scottish children, 80.6 % of all of the 8057 restorations placed were amalgams in posterior teeth.252 Because of the high frequency of use, the dental profession has tried to monitor potential effects on dental personnel. This year a national survey of risks for women dentists was initiated, including monitoring amalgam use and mercury exposure.253 Although there is still insufficient information about some risks, the current information from side-effects surveys on biomaterials conducted in Scandinavia indicate that allergies are relatively low and that acrylic resin-related incidents are much greater than any reports for amalgam or Hg.254 A succinct summary of mercury hygiene measures for a dental operatory has been prepared by the American Dental Association (ADA). 255At present, these measures do not include amalgam and mercury traps for office effluent. There is increasing concern by the Environmental Protection Agency (EPA) that these should be contained, but there is inadequate evidence about the relative efficiency of these devices.256 In January 1992, the ordinance in an Arizona county against mercury discharges from dental offices was suspended. 25’iFor the very near future there is no evidence that the EPA will strictly enforce such regulations. In vitro cell culture tests of cytotoxicity have not always been reliable indicators of bioactivity in humans but do indicate relative risks. In vitro tests of amalgam phases and elements demonstrated that the major toxic reactions were due to Cu and Zn elements, or gamma-one plus Sn plus Zn matrix.258 The presence of Zn appeared to amplify the cellular reactions. The major dilemma for the use of amalgam is effective education of patients in light of the misinformation from the “60 Minutes” program. A summary of the key events in 1991 follows. In response to the “60 Minutes” program, the ADA president, Dr. Truono,25g published a letter in February sent to the program director. The letter dealt in detail with 163

JENDRESEN

all of the points of misinformation and condemned the distortions in the program. The ADA developed detailed informational aids for dentist use with patients.260 Over the next couple of months, several excellent summary articles were published by the Journal of the American Dental Association.261-264 The article by Mackert provided an outstanding scientific review of the issuefor clinicians (not patients). The currently measuredexposure levels are 1.2 @g/dayfor eight amalgams,or 0.15pg/amalgam/day.These levels represent approximately 5 % to 10% of the daily mercury intake from all sourcesand are far belowthe published levels for toxicity. The number of hypersensitive patients is lessthan 3 % of the population and probably less than 0.6% showany clinical manifestations. Those manifestations are mild and short lived, even if detected.261 The most commonchallenging question about mercury hazards is why the professioncannot prove that amalgam is safe.For any substance,the dosemakesthe poison!Current estimatesfor human Hg exposuresfrom dental amalgamsplacethe averagelevelsat 1.2-1.7pg/day which is only about 1% of the Occupational Safety and Health Administration (OSHA) regulation level. Many dental officesin the United States still are not in full compliancewith all current mercury hygiene measures. Therefore the ADA continues to test dentists and staffs, whoselevels arewell abovethe generalpopulation levelsfor mercury but appear to be well below toxic levels. One of the major argumentsby the anti-amalgamistsfor amalgamtoxicity wasa publishedstudy usingseveralsheep as test animals to monitor the systemic distribution of mercury after the insertion of 16 occlusalamalgams.265, 266 This work was flawed for numerous reasons,the least of which the amalgamswere overfilled in the teeth and the normal hypereruption of the teeth during wear allowedthe amalgamsto be effectively consumedduring the 30-day test period. In any case,this information wastouted asscientific evidence of the problem for humans. During the first part of the year there were numerous excellent editorials and thoughtful letters to editors that reviewed the errors in the “60 Minutes” program.267-27g In addition to all of the scientific evidencein favor of dental amalgamuse, there are two other points of interest. The first is the potential control by the EPA of dental office effluent at sometime in the future. Becauseof numerous pollution concernsand problemswith other heavy metals suchaslead, mercury may be banned or strictly controlled. If dentistry doesnot receive an exception from any such rules, it will probably be too expensiveto capture amalgam and/or mercury from effluents.276This would create significant pressureto shift to alternative filling materials. The secondconcern is the relative cost of replacing amalgam restorations. For whatever purpose, the replacement of amalgamswould be excessively expensive. Meskin has calculated that if 1% of the amalgamsin the United States were replacedannually with an alternative, it could cost 25 billion dollars per year. 164

ET AL

In responseto the public outcry, the FDA reviewed the classification category for dental amalgam in a public hearing on March 15,199l in Washington D.C. They concluded that although much researchwas still neededfor amalgam,amalgamsshould not be replaced.280However, their final determinations about the safety of amalgam were postponed until the end of the 1991 year, pending other ongoinginvestigations of risk. During the latter part of the 1980sthe professionrelied heavily on a review of the amalgamcontroversy published in Consumer Reports281 asa neutral view. It concludedthat amalgamsweresafe!In April of 1991,Consumer Reportsza2 revisited the controversy and again concluded the same thing. The new article is more patient-oriented and deals with all of the details of the controversy that the “60 Minutes” program brought up. It is an excellent article for patient use.Patient information is strongly needed.A recent survey in Finland perceptions of pregnant patients reported that 43 % of the patients opposedany dental treatment and 77% opposeddental amalgam use becauseof potential risks in fetal development.283 The National Institute of Dental Research (NIDR)284 organized and held a conferenceon the risk assessment of all restorative dental materials in August 1991 at the National Institutes of Health (NIH) in Washington, D.C. Although all materials were considered, the primary focus was amalgam.A broad-basedpanel that heard presentations and discussionsof the scientific evidence concluded that more researchwasneeded but the overwhelming evidence wasthat amalgamwas safe.285 Much more refined understandingsof mercury toxicity are slowly being reported. The key point in the early controversy wasthe level of exposure. The early calculations of exposure levels were reanalyzed, debated, and reported.286-288 Previous arguments about T-lymphocyte level changesas part of an immune responseto mercury from amalgamswerecountered by a human study of groupswith and without amalgams.28g One of the prominent anti-amalgamistsin the newswas Dr. Joel Berger from New York City. His practice wassuspendedby the New York State Board of Dentistry because he was removing amalgamsfor reasonsof diseasetreatment. After appeal for reinstatement, the appellate court in New York on December 12, 1991, affirmed the State Board’s decision and denied the appea1.2g0 Despitethe many successfuldefensesof dental amalgam, the future for dental amalgamisnot clear. Nashsglreported that from 1979 to 1990,there has been a 38% decline in amalgamplacement. Part of this may be due to better amalgamsurvival but there may also be significant use of alternative materials. During the sameperiod, glassionomer usehasincreaseddramatically. In a survey of Belgian dentists’ use of restorative materials from 1983 to 1988, amalgamremained the dominant choice, but there were someincreasesin compositeand glassionomer use.2g2 New versions of light-cured products are much lesstechnique-

JULY

1992

VOLUME

68

NUMBER

1

COMMITTEE

REPORT

sensitive and are being strongly advocated for use.2g3 All alternatives are more expensive.2g4 During the next decade, much less amalgam use is expected. Existing amalgams are probably being replaced at a much faster rate than necessary because of general misinterpretation of the relative importance of margin fracture.2g5 Composite

restorations

New fillers are in the process of being developed for composites. Novel silicate fillers have been developed that match the refractive index of the glass to the resin.2g6 TiOs-SiOs glasses are being produced by the sol-gel process using up to 20% titanium dioxide and heating to 1000’ C. These fillers allow excellent light transmission (tenfold better) and produce 96% instead of 57% monomer conversion during curing. In addition, calcium metaphosphates (CMP), either as vitreous or beta-crystalline forms, are being considered for resin composites and cements.2g7 The megafilled composite system (glass-ceramic inserts) finally is commercially available.2g8 It is based on borosilicate glass ceramic pieces of varying size for insertion into class I, II, or III composites. Their volume decreases polymerization shrinkage of the composite. The excellent abrasion resistance provides protection against occlusal surface wear. A major concern for the composite matrix is polymerization shrinkage during curing, which may also contribute to debonding and/or margin gap formation. A new laboratory method has been developed to monitor polymerization shrinkage kinetics. 2ggAn interesting experiment with reduced light intensity from the polymerization unit slowed curing, allowing more composite flow during setting, and preserving acceptable interfacial bonding.300 The effects of polymerization may also strain bonded tooth structure. Strain gauges on teeth undergoing composite curing indicated less strain with a more highly filled material, P-50 (3M, St. Paul, Minn.) versus Herculite XR (Kerr, USA) or Silux (3M).301 However, cyclic loading may produce fatigue fracture of the bond and/or restoration relatively quick.302s 303Doubling a fatigue load from 11 to 22 pounds shortened the bonded restoration survival to only 2600 cycles.302This is equal to only one day of clinical cycling. Increasing filler content correlated with better bonding in laboratory studies of shrinkage effects.304 Cavity design itself contributes to some of the observed debonding effects during polymerization shrinkage. Internally rounded cavities for class II composites showed reduced gap formation.305 The degree of cure that occurs is a function of the polymerization light access. Complex restorations with clear matrix bands and/or mirrored surface matrix bands showed improved surface hardness.306 Most in vitro wear tests show poor correspondence with clinical wear results. Therefore, it has been difficult to rate the importance of in vitro results. Taber abrader wear tests produced wear curves similar to those observed in clinical studies, but the authors failed to provide any evidence that

THE

JOURNAL

OF PROSTHETIC

DENTISTRY

similar mechanisms of wear were occurring.ao7 Three-body wear testing with soft and hard abrasives failed to duplicate the wear patterns observed in vivo.30s A number of composite wear mechanisms were explored this past year. Toothbrush wear has been suggested to produce as much wear as food abrasion. After 20,000 toothbrush strokes with varying dentifrices, composite surfaces became roughened to a greater degree than the particle size of the filler.30g This seemed to indicate that more than polymer erosion was occurring. This roughness was compared with that for enameL310 In a separate study, enamel wear was recorded by use of intraoral replicas in monkeys and humans to monitor effects of hard and soft diets.311 Monkeys chewing abrasive food produced new features in enamel surfaces on premolars and molars in less than 7 days. In addition to natural wear, artificial wear can be easily produced by air-abrasive tooth cleaning procedures.312 Detrimental effects were induced by only 5 seconds of air-abrasion at 100 psi. Increasing popularity for whitening and bleaching agents suggested that some procedures might alter composite surfaces, but testing of three commercial products indicated all effects were minor and probably clinically insignificant313 One of the earliest hypotheses for composite wear was the degradation of the resin matrix by intraoral food and water absorption. Wear tests continue to try to simulate the proposed effect by exposing composites to 75 % ethanol in water solutions.314 An important recent qualification of the original evidence for that hypothesis arose when artifacts were documented in the experimental technique.315 Although this hypothesis has not been totally discounted, there is increasing suspicion as to its clinical relevance. In addition to composite wear, in vivo color changes, which have been clinically observed, have been assigned to food absorption effects and/or ultraviolet light. However, an in vitro study of 16 materials in water and with long-term sunlight exposure showed only relatively minor effects on color change. 316This area remains poorly understood. Radiopacity has always been a desirable quality for posterior composites, yet difficult to achieve because the reinforcing fillers were usually based more on unmodified SiOs compositions. An outstanding assessment of appropriate radiopacity was reported by Espelid et a1.317Class II preparations using three different composites and one amalgam were successively filled and evaluated by 11 dentists for radiopacity. By an ROC method, the result was that optimal radiopacity was a semiopaque restoration with just slightly more radiopacity than enamel. In a separate study, 55 anterior and posterior composites were rated for radiopacity against an aluminum step wedge.318 The enamel control was rated 198 and dentin was rated 107 on that scale. The results were that 17 composites were more radiopaque than enamel and 19 were less radiopaque than dentin. Some posterior composites were in the latter group. In the past two years there have been reports of chemical 165

JENDRESEN

decomposition of the resin matrix and/or unreacted monomer providing leachable components. Composites exposed to saliva and porcine liver esterase showed superficial changes, including reduced microhardness and evidence of MMA release.31g In vitro tests of composite cylinders immersed 7 days in water showed 0.1% Bis-GMA and 1.4% TEGDMA release.320 Most unreacted monomer was not released. Continued curing further reduced the detectable amounts. Cytotoxic effects with cultured mammalian fibroblasts were measured.321 Ethoxylated BIS-GMA release was the most toxic. The inhibitors and accelerators were generally the least toxic. Other monomers and diluents were intermediate. The percent of conversion of composites affected the amount of releasable monomer and the cell culture results.322 Finishing and polishing of composites depends on the filler type and content. The effects of Mylar (Du Pont Co., Wilmington, Del.) strips, unfilled resin glazes, polishing with three grades of rubber points, and aluminum oxide disks were evaluated on anterior and posterior composites.323 The investigators concluded that nothing was ideal for all composites. Finishing with aluminum oxide disks produced equal or better surface finishes on all composites when finishing was conducted dry versus wet.324 An advantage of composites versus amalgams is the option for resurfacing by bonding new composite onto old composite after unwanted wear or color changes. This option continues to receive more attention. Previous reports seemed to indicate relatively good adhesion of new to old composite, but present reports indicate that less than ideal rebonding may occur for newer systems. Repairs with three self-curing and three visible light-curing products in different combinations, for times stored in water up to 365 days, showed only 19% to 52% of original tensile bond strengths.325 A range of variables was investigated for P-30 (3M) repairs with different techniques that only achieved 25% to 50% of original strengths.326 However, using correct bonding agents as part of the rebonding procedure seemed to produce clinically acceptable results.327 A key in successful rebonding is apparently adequate wetting for intimate micromechanical bonding. The wettability of various monomers on a range of polymers showed that monomers spread better in general on BIS-GMA substrates than on UDM ones. Spreading was calculated from contact angle, surface tension, and viscosity information.328 Rebonding factors seem to be influenced by the same factors governing enamel and dentin bonding. Clinical studies of composites are necessarily slow and expensive. However, more are required until appropriate in vitro and in vivo results can be correlated.32g For the most part, the studies continue to focus on wear resistance of posterior composite restorations. Results are reported in terms of direct U. S. Public Health Service evaluations or indirect evaluation values. Alternative techniques may produce better accuracy, but are much more expensive.330 Several key points continue to be confirmed by ongoing 166

ET AL

studies. Microfills show good wear performance and are popular despite earlier predictions.331 Occlusal wear rates decrease with time332 and approach very low levels in conservative class II preparations.333 The decreasing wear rate can be described semilogarithmically as a function of time. Newer composites meet the original ADA standard limit of

Report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry.

The committee screened several hundred articles, citing 518 published papers. Some are present quality in research, others provide clinical interest, ...
8MB Sizes 0 Downloads 0 Views