Scand. J. Dent. Res. 1975: 83: 193—201 (Key words: dentat ptaque; dental restorations)
Presence or absence of plaque on subgingival restorations JENS WAERHAUG Department of Periodontics, Faculty of Dentistry, University of Oslo, Oslo, Norway ABSTRACT — One hundred and eight extracted teeth with restorations placed below the gingival margin were stained and examined under the stereomicroscope with the aim of scoring presence or absence of subgingival plaque. Individual observations showed that a subgingival restoration can be completely covered with plaque in as short a time as 6 weeks and it can be free of plaque for as long as 2 years. In the material as a whole about 9 out of 10 of the restorations were covered with plaque subgingivally. Since the material is selected, these proportions cannot be claimed to be valid for the population as a whole, but the observations suggest that plaque sooner or later will accumulate on most if not all subgingival restorations. Rough surfaces and or inadequate marginal adaptation are likely to facilitate a more rapid adherence of bacteria to the restorations than to the smooth tooth surface. It is concluded that restorations placed below tlie gingival margin indirectly are strongly involved in the etiology of destructive periodontal disease and the cause of many extractions. (Received for publication 20 January, accepted 3 March 1975)
Experimental investigations in animals have shown that the common materials used in crown and bridge dentistry such as gold, acrylic resin and porcelain are inert for all purposes (WAERHAUG 1953, 1956, 1957). There is evidence to show that the various cements (Fig. 1) exert some chemical irritation, but the inflammation it causes does not extend in depth and it is not likely to cause loss of attachm,ent (WAERHAUG 1956). The same kind of chemical irritation can also be expected from amalgam fillings (ZANDER 1957). However, a common finding in most animal experiments was that the subgingival restorations soon became covered with plaque as shown in Fig. 2, and the toxic irritation from the latter causes se-
vere inflammation and loss of attachment (KARLSEN
1970,
WAERHAUG
1953,
1956;
& ZANDER 1957). The aforementioned observations in experimental animals have been corroborated by several epidemiologic investigations in man which have shown that there is more inflanmiation adjacent to teeth with than without restorations, and that full and partial crowns contribute to the accumulation of plaque (SILNESS 1970). The problems created by subgingival restorations have been reviewed in further detail by the author (WAERHAUG 1960, 1972). The importance of plaque in the etiology of gingivitis has been convincingly demonstrated in several clinical studies (LoE, THEILADE & JENSEN 1965). HowWAERHAUG
194
WAERHAUG
Fig. i. Cement filling in a buccal cavity (monkey). Cement dissolved in acid. Observation period 10 months. Epithelium is in contact with cement up to arrow. There is only moderate inflammation in adjacent tissue, indicating little if any irritation from this material. From arrow upward subgingival plaque has been formed, and it has caused some inflammation. Fig. 2. Cement filling in a buccal cavity (monkey). Observation period 7 months. Plaque retained on the cement filling in cervical part. Note that facing the plaque, pocket epithelium is extremely thin, and subjacent connective tissue is heavily inflamed. On marginal part of filling there is no plaque. The corresponding pocket epithelium is thick and subjacent connective tissue is less inflamed. Clinically, gingiva was classified as healthy. There is a loss of attachment of 1 mm below the cemento-enamel junction. Sections cut immediately outside the filling showed a normal dento-enamel junction and no loss of attachment. •
ever, by clinical methods only the presence of supragmgiva.1 plaque can be established. Ahhough the supragingival plaque can cause marginal gingivitis, it seldom leads to loss of attachment. Destructive periodontal disease is usually caused by the 5tifogingival plaque, and for that reason the subgingival plaque is more interesting from an etiological point of view (LINDHE, HAMP & LOE 1973). Up to the present time there has been
no clinical method hy means of which the presence of ^w&gingival plaque can be established. This problem has been partly solved by the introduction of "a method for evaluation of periodontal problems on extracted teeth" (WAERHAUG 1973, 1975). This method is particularly useful for the study of human m.aterial which ordinarily would requiie that biopsies be taken for histologic examination. For ethical reasons such biopsies can seldom be collected,
PLAQUE ON DENTAL RESTORATIONS but fortunately most of the observations can be made on the extracted tooth alone. Thus, if a tooth is properly stained, any plaque on its surface will be disclosed, and if a landmark is made at the gingival margin, any plaque cervically to this line must be subgingival. In fact, this is just to apply the disclosing solution method after extraction of the tooth. In the present investigation this method was used in an attempt to establish to what extent dental restorations which have been finished below the gingiva are covered with plaque in the subgingival area.
195
Material and methods
The material consists of 108 teeth with restorations placed below the gingival margin. Fiftynine of the teeth were extracted by the author, some of them because of periodontal involvement. Forty-nine teeth were provided by six dentists, practicing in suburban or rural areas in Norway. Caries to the pulp and periapical problems were the most common cause of extraction of the latter teeth. Prior to extraction, a notch was made in the tooth surface at the level of the gingival margin (WAERHAUG 1975) to serve as a landmark for the subsequent examination of the stained tooth under the stereomicroscope. The reader is advised to examine Fig. 3 thoroughly in order to understand the basic principles of evaluating periodontal prob-
Fig. 3. To the left, photomicrograph of the tissue adjacent to an acrylic resin filling which was dissolved in acid. At gingival margin a notch is made through the plaque into the filling. Right diagram is made on the basis of 47 serial sections, one of which is the photomicrograph shown here. The diagram indicates what the tooth with the filling would have looked like, if it had been extracted and stained, and it shows distribution of subgingival plaque on filling. Note little if any subgingival plaque on tooth outside filling.
196
WAERHAUG Table 1
..
Distributions of the various materials used for restorations Type of restoration
No.
Amalgam Gold Cement Zinc oxide-eugenol Acrylic
ft E
Subgingival with plaque
m
7 4
71 6 13 5 4
108
99
lems on extracted teeth. The photomicrograph to the left is one of 47 serial sections through the tissue adjacent to an acrylic filling which had been dissolved in chloroform. Plaque covers the filling in the marginal half, and it had caused heavy inflammation in the adjacent soft tissue. A notch is supposed to have been made through the plaque into the filling at the gingival margin. The right diagram was made on the basis of measurements in the serial sections, and it shows what the tooth with the filling would have looked like if it had been extracted and stained. The notch at the gingival margin would have appeared as a furrow around the tooth, and any plaque below this furrow would be ^ufogingival. The stained extracted tooth would have revealed all that the 47 serial sections did regarding the distribution of the subgingival plaque. In fact, the extracted tooth gives a much better opportunity to study the consequences of subgingival restorations than do the histologic sections, and the method is much quicker and less expensive. In Fig. 3 measurements in serial sections , were used to visualize the tooth after extraction. However, in the present context, it is even more important that the reader develops the ability to reverse these visual impressions, i.e., when looking at a stained extracted tooth with a subgingival filling, covered with plaque, he must be able to visualize what the histologic picture of a given area of the soft tissue would have looked like if a section had been cut through it with tlie tooth in situ. Table 1 shows the distribution of the various materials used for the restorations. In retrospect, only those patients who had gotten their restorations within the last year or so where able to tell when they had been made, and these cases were scarce. Thus, the observation period
Subgingival without plaque
I
may have ranged between a few weeks and several decades. In the about 20 cases in which the observation period was known, the shortest period in which a restoration was completely
Fig. 4. Molar with amalgam filling which had been located partly below gingival margin. Supragingival part of filling was completely covered with plaque but most of the subgingival part is plaque-free.
PLAQUE ON DENTAL RESTORATIONS
197
Fig. 5. Amalgam filling made about 2 years before extraction of the tooth. Subgingival part of filling was completely covered with plaque and the plaque had also proliferated in apical direction from filling margin to extent indicated by arrows. Subgingival scaling carried out 5 months before extraction, demonstrating limitation of this kind of treatment when restorations are present. covered with plaque was 6 weeks (Fig. 6), and the longest period a restoration was found to be free of plaque was 2 years. The teeth, which were extracted by the author, were immediately, and without fixation, stained in toluidine blue, basic fuchsin or crystal violet. The teeth obtained from the other dentists were fixed in formalin and stained by the author. The teeth were air dried and examined under the stereomicroscope. Results
Table 1 shows that 99 out of the 108 restorations were covered with plaque; in some cases the plaque was found on top of calculus. Some photographs which illustrate typical conditions will be shown. In Fig. 4 there is a plaque-free zone on the amalgam filling below the gingival margin. Here the amalgam with a cuticle
on top of it had been in contact with the pocket epithelium (epithelial cuff), and it can safely be concluded that the inflammatory reaction in the soft tissue had been slight and of about the same severity as in Fig. 1. This filling was classified as plaque-free even if there is some subgingival plaque shortly below the gingival margin. Fig. 5 shows the mesial surface of a molar with an amalgam filling. The filling had been made about 2 years before the extraction and subgingival scaling had been carried out twice a year, the last time 5 months before extraction. If absence of subgingival plaque is taJken as evidence that a healthy epithelial cuff had reappeared in the curetted area, the healing had been p>erfect adjacent to the
198
Fig. 6. enamel surface dicated
WAERHAUG
Zinc oxide-eugenol filling placed 3 mm below gingival margin and ending at cementojunction. Filling is completely covered with plaque. Note that there is no plaque on tooth on both sides of filling. There is a loss of attachment of about 1.0 mm below filling as inwith arrows. Observation period 6 weeks.
tooth. Even a piece of calculus, C, left behind during the scaling, was free of plaque, and consequently non-irritating. However, the amalgam filling was completely covered with plaque. The plaque had even grown about half a millimeter in apical direction from the margin of the filling, as indicated with the arrows. Fig. 6 shows a temporary zinc-oxide eugenol filling which had been in place for 6 weeks. It is completely covered with plaque, and there is even a loss of attachment of about 1 mm due to the bacterial inflammation. The amalgam filling shown in Fig. 7 had, according to the patient, been made about 8 months earlier. In this study it was listed as "without plaque" because not all the subgingival part of it was cov-
Fig. 7. Amalgam filling placed about 8 months before extraction. Cervical part of filling is still plaque-free, but plaque had developed to about 1.0 mm below gingival margin. There is no plaque on subgingival part of tooth on either side of the filling.
PLAQUE ON DENTAL RESTORATIONS ered with plaque. However, it is obvious that plaque is rapidly being formed. Very few amalgam fillings had been polished. Fig. 4 had been polished and it is possible that this had contributed to the favorable restilt. In practically all cases overhangs were observed. The overhangs in Figs. 4, 5 and 7 measured 0.5, 1.2 and 1.0 mm respectively. There was always some space between the amalgam filling and the tooth, as shown in Figs. 4 and 7. What is said about the technical standard of the amalgam fillings holds true for the rest of the restorations. Between the crowns and the preparations there were always defects. Discussion
In evaluating these observations it should be kept in mind that the material is selected and that the percentage of subgingival restorations covered with plaque observed here cannot be claimed to be representative for the Norwegian population as a whole. Let us assume, and hope, that the conditions are better, but the fact still remains that a large proportion of the restorations which are placed below the gingival margin are likely to be covered with plaque within weeks, months or years. The findings made here do not allow conclusions to be drawn regarding the average time needed for plaque to cover a subgingival restoration and to what extent there are differences between the various materials and types of restorations. However, the observations that a zinc oxideeugenol filling (Fig. 6) was completely covered with plaque in 6 weeks, and that an amalgam filling (Fig. 7) was mostly covered in about 8 months, at least indicate that plaque develops fast in some cases. Indeed, this problem merits further experimental investigation. There may be several reasons wKy
199
plaque accumulates so much faster on restorations than on a plain tooth surface: (1) the surfaces of materials like cements (Fig. 1 and 6) and axnalgam (Figs. 4, 5 and 7) are rough as estimated by microbiologic standards, even if they are polished (Fig. 4), (2) spaces between restorations and preparations (Figs. 3 & 4) which may look negligible when estimated by technical standards, are likely to be very important from a microbiologic point of view. In addition, none of the restorations in this material fulfilled the requirements of technical perfectionism even when examined with the naked eye, and (3) physicochemical qualities of amalgam and cements may directly contribute to the attachment of plaque-bacteria. . In order to understand what happens in the soft tissue adjacent to a subgingival restoration it is essential to be familiar with some basic features of the healthy gingival pocket. Under physiologic conditions the dentoepithelial junction seals the hole in the epithelium created by the tooth. This epithelial cuff which clinically is the soft tissue wall of the healthy gingival pocket is a dynamic tissue. Bacteria which are brought into the pocket during clinical procedures are washed out or killed within minutes or hours, and the integrity of the dentogingival junction is reestablished. (WAERHAUG 1952). This is a highly important defense mechanism, and it appears as if a smooth tooth surface is one of the requirements for the series of reactions to take place in an adequate way. When the smooth tooth surface is replaced with a foreign body with all the above mentioned deficiencies, the defense mechanism is apparently impeded in its function and the result is rapid plaque formation. In fact, from a biologic point of view it is not surprising that such an interference takes place. When the plaque organisms have gotten
200
WAERHAUG
a foothold on the filling they induce inflammation in the adjacent soft tissue and sooner or later this will lead to loss of attachment. How quickly attachment can be lost is well demonstrated in Fig. 6. Within 6 weeks the zinc oxide-eugenol filling was completely covered with plaque subgingivally, and the inflammation induced by the microorganisms had broken down the periodontal fibers to a distance of about 1 mm below the filling as indicated with the arrows. In fact, the speed of the destruction of the attachment apparatus in cases like Figs. 5 and 6 will be determined by the ability of the plaque-organisms to proliferate in apical direction from their base on the restoration. Fig. 6 represents a fairly common situation in practice. Deep approximal caries undermines the enamel and the cavity is easily extended to the bottom of the pocket which in young individuals corresponds to the cemento-enamel junction, as was the case here. The cavity may be filled with amalgam., cement or some other material, which as previously mentioned facilitates retention of bacteria. In the case of Fig. 6 this means that the filling brought the plaque to a position which was about 3 mm further apically than it was on the tooth on both sides. For the plaque to proliferate the same distance on a smooth tooth surface might take 10-30 years. This is why restorations are so relevant in the etiology of periodontal disease. Another problem created by subgingival restorations is that routine periodontal treatment such as subgingival scaling has a limited effect. At best, such treatment can prevent the plaque from spreading too far apically from the filling margin, as was attained in the case of Fig. 5. But even the most perfect subgingival scaling will not prevent rapid reformation of plaque on the filling itself as can rou-
tinely be attained on a plain tooth surface (see both sides of the filling in Fig. 5). Prevention of secondary caries by extending restorations to below the gingival margin creates periodontal problems which eventually may lead to the loss of the tooth. At a time when these consequences of subgingival restorations were unknown there was good reason to extend the filling, but with our present knowledge there is a good reason for not doing so. Fortunately there is an alternative. Recent clinical trials by AXELSSON & LINDHE (1974) have shown that both primary and secondary caries can be prevented by proper oral hygiene measures. Restorations placed below the gingival margin are likely to accumulate plaque subgingivally even if routine oral hygiene is maintained. Plaque is quickly reformed on subgingival fillings after scaling. Plaque on subgingival restorations can lead to loss of attachment.
References
P. & LINDHE, J.: The effect of a preventive programme on dental plaque, gingivitis and caries in schoolchildren. Results after one and two years. / . Clin. Feriodontol. 1974: 1: 126-138. KARLSEN, K . : Gingival reactions to dental restorations. Acta Odontol. Scand. 1970: 28: 895-904. AXELSSON,
LINDHE, J., HAMP, S. E . & LOE, H . : Experi-
mental periodontitis in the beagle dog. / . Periodontal Res. 1973: 8: 1-10. LOE, H . , THEIL.-VDE, E . & JENSEN, S. B.: Experimental gingivitis in man. / . Periodontol. 1965: 36: 177-187. SILNESS, J.: Periodontal conditions in patients treated with dental bridges. / . Periodontal Res. 1970: 5: 60-68. SILNESS, J.: Periodontal conditions in patients treated with dental bridges. II. The infiuence of full and partial crowns on plaque accumulation, development of gingivitis and pocket formation. / . Periodontal Res. 1970: 5: 219224.
PLAQUE ON DENTAL RESTORATIONS J.: Periodontal conditions in patients treated with dental bridges. III. The relationship between the location of the crown margin and the periodontal condition. /. Periodontal Res. 1970: 5: 225-229. SILNESS, J.: Periodontal conditions in patients treated with dental bridges. V. Effect of splinting of adjacent abutment teeth. /. Periodontal Res. 1974: 9: 121-126. WAERHAUG, J . : The gingival pocket. Anatomy, pathology, deepening and elimination. Thesis. Odontol. Tidskr. 1952: 80: Suppl. 1. WAERHAUG, J.: Tissue reaction around artificial crowns. / . Periodontol. 1953: 24: 172-185. WAERHAUG, J.: Effect of zinc phosphate cement fillings on gingival tissues. ./. Periodontol. 1956: 27: 284-290. WAERHAUG, J.: Observations on extracted i:eeth plated with gold foil. Oral Surg. 1956: 9: 780-791. WAERHAUG, J. & ZANDER, H . A.: Reaction of gingival tissues to selfcuring acrylic restorations. /. Am. Dent. Assoc. 1957: 54: 760768. SILNESS,
Address: Department of Periodonties Faculty of Dentistry 69 Geitmyrsveien Oslo 3 Norway
201
J.: Tissue reactions around acrylic root tips. /. Dent. Res. 1957: 36: 27-38. WAERHAUG, J.: Histologic considerations which govern where the margins of restorations should be located in /elation to the gingiva. Dent. Clin. North Am. 1960: 161-176. WAERHAUG, J.: Dental restorations as cause of periodontal destruction. Audiovisual program (53 slides). Department of Periodonties, University of Oslo. Oslo 1972. Available on request. WAERHAUG, J.: A method for the evaluation of periodontal problems on extracted teeth. Audiovisual program (29 slides). Department of Periodonties, University of Oslo, Oslo 1973. Available on request. WAERHAUG, J.: A method for evaluation of periodontal problems on extracted teeth. /. Clin. Periodontol. 1975: 2: in press. ZANDER, H . A.: Effect of silicate cement and amalgam on the gingiva. /. Am. Dent. Assoc. 1957: 55: 11-15. WAERHAUG,
Presence or absence of plaque on subgingival restorations JENS WAERHAUG Department of Periodontics, Faculty of Dentistry, University of Oslo, Oslo, Norway ABSTRACT — One hundred and eight extracted teeth with restorations placed below the gingival margin were stained and examined under the stereomicroscope with the aim of scoring presence or absence of subgingival plaque. Individual observations showed that a subgingival restoration can be completely covered with plaque in as short a time as 6 weeks and it can be free of plaque for as long as 2 years. In the material as a whole about 9 out of 10 of the restorations were covered with plaque subgingivally. Since the material is selected, these proportions cannot be claimed to be valid for the population as a whole, but the observations suggest that plaque sooner or later will accumulate on most if not all subgingival restorations. Rough surfaces and or inadequate marginal adaptation are likely to facilitate a more rapid adherence of bacteria to the restorations than to the smooth tooth surface. It is concluded that restorations placed below tlie gingival margin indirectly are strongly involved in the etiology of destructive periodontal disease and the cause of many extractions. (Received for publication 20 January, accepted 3 March 1975)
Experimental investigations in animals have shown that the common materials used in crown and bridge dentistry such as gold, acrylic resin and porcelain are inert for all purposes (WAERHAUG 1953, 1956, 1957). There is evidence to show that the various cements (Fig. 1) exert some chemical irritation, but the inflammation it causes does not extend in depth and it is not likely to cause loss of attachm,ent (WAERHAUG 1956). The same kind of chemical irritation can also be expected from amalgam fillings (ZANDER 1957). However, a common finding in most animal experiments was that the subgingival restorations soon became covered with plaque as shown in Fig. 2, and the toxic irritation from the latter causes se-
vere inflammation and loss of attachment (KARLSEN
1970,
WAERHAUG
1953,
1956;
& ZANDER 1957). The aforementioned observations in experimental animals have been corroborated by several epidemiologic investigations in man which have shown that there is more inflanmiation adjacent to teeth with than without restorations, and that full and partial crowns contribute to the accumulation of plaque (SILNESS 1970). The problems created by subgingival restorations have been reviewed in further detail by the author (WAERHAUG 1960, 1972). The importance of plaque in the etiology of gingivitis has been convincingly demonstrated in several clinical studies (LoE, THEILADE & JENSEN 1965). HowWAERHAUG
194
WAERHAUG
Fig. i. Cement filling in a buccal cavity (monkey). Cement dissolved in acid. Observation period 10 months. Epithelium is in contact with cement up to arrow. There is only moderate inflammation in adjacent tissue, indicating little if any irritation from this material. From arrow upward subgingival plaque has been formed, and it has caused some inflammation. Fig. 2. Cement filling in a buccal cavity (monkey). Observation period 7 months. Plaque retained on the cement filling in cervical part. Note that facing the plaque, pocket epithelium is extremely thin, and subjacent connective tissue is heavily inflamed. On marginal part of filling there is no plaque. The corresponding pocket epithelium is thick and subjacent connective tissue is less inflamed. Clinically, gingiva was classified as healthy. There is a loss of attachment of 1 mm below the cemento-enamel junction. Sections cut immediately outside the filling showed a normal dento-enamel junction and no loss of attachment. •
ever, by clinical methods only the presence of supragmgiva.1 plaque can be established. Ahhough the supragingival plaque can cause marginal gingivitis, it seldom leads to loss of attachment. Destructive periodontal disease is usually caused by the 5tifogingival plaque, and for that reason the subgingival plaque is more interesting from an etiological point of view (LINDHE, HAMP & LOE 1973). Up to the present time there has been
no clinical method hy means of which the presence of ^w&gingival plaque can be established. This problem has been partly solved by the introduction of "a method for evaluation of periodontal problems on extracted teeth" (WAERHAUG 1973, 1975). This method is particularly useful for the study of human m.aterial which ordinarily would requiie that biopsies be taken for histologic examination. For ethical reasons such biopsies can seldom be collected,
PLAQUE ON DENTAL RESTORATIONS but fortunately most of the observations can be made on the extracted tooth alone. Thus, if a tooth is properly stained, any plaque on its surface will be disclosed, and if a landmark is made at the gingival margin, any plaque cervically to this line must be subgingival. In fact, this is just to apply the disclosing solution method after extraction of the tooth. In the present investigation this method was used in an attempt to establish to what extent dental restorations which have been finished below the gingiva are covered with plaque in the subgingival area.
195
Material and methods
The material consists of 108 teeth with restorations placed below the gingival margin. Fiftynine of the teeth were extracted by the author, some of them because of periodontal involvement. Forty-nine teeth were provided by six dentists, practicing in suburban or rural areas in Norway. Caries to the pulp and periapical problems were the most common cause of extraction of the latter teeth. Prior to extraction, a notch was made in the tooth surface at the level of the gingival margin (WAERHAUG 1975) to serve as a landmark for the subsequent examination of the stained tooth under the stereomicroscope. The reader is advised to examine Fig. 3 thoroughly in order to understand the basic principles of evaluating periodontal prob-
Fig. 3. To the left, photomicrograph of the tissue adjacent to an acrylic resin filling which was dissolved in acid. At gingival margin a notch is made through the plaque into the filling. Right diagram is made on the basis of 47 serial sections, one of which is the photomicrograph shown here. The diagram indicates what the tooth with the filling would have looked like, if it had been extracted and stained, and it shows distribution of subgingival plaque on filling. Note little if any subgingival plaque on tooth outside filling.
196
WAERHAUG Table 1
..
Distributions of the various materials used for restorations Type of restoration
No.
Amalgam Gold Cement Zinc oxide-eugenol Acrylic
ft E
Subgingival with plaque
m
7 4
71 6 13 5 4
108
99
lems on extracted teeth. The photomicrograph to the left is one of 47 serial sections through the tissue adjacent to an acrylic filling which had been dissolved in chloroform. Plaque covers the filling in the marginal half, and it had caused heavy inflammation in the adjacent soft tissue. A notch is supposed to have been made through the plaque into the filling at the gingival margin. The right diagram was made on the basis of measurements in the serial sections, and it shows what the tooth with the filling would have looked like if it had been extracted and stained. The notch at the gingival margin would have appeared as a furrow around the tooth, and any plaque below this furrow would be ^ufogingival. The stained extracted tooth would have revealed all that the 47 serial sections did regarding the distribution of the subgingival plaque. In fact, the extracted tooth gives a much better opportunity to study the consequences of subgingival restorations than do the histologic sections, and the method is much quicker and less expensive. In Fig. 3 measurements in serial sections , were used to visualize the tooth after extraction. However, in the present context, it is even more important that the reader develops the ability to reverse these visual impressions, i.e., when looking at a stained extracted tooth with a subgingival filling, covered with plaque, he must be able to visualize what the histologic picture of a given area of the soft tissue would have looked like if a section had been cut through it with tlie tooth in situ. Table 1 shows the distribution of the various materials used for the restorations. In retrospect, only those patients who had gotten their restorations within the last year or so where able to tell when they had been made, and these cases were scarce. Thus, the observation period
Subgingival without plaque
I
may have ranged between a few weeks and several decades. In the about 20 cases in which the observation period was known, the shortest period in which a restoration was completely
Fig. 4. Molar with amalgam filling which had been located partly below gingival margin. Supragingival part of filling was completely covered with plaque but most of the subgingival part is plaque-free.
PLAQUE ON DENTAL RESTORATIONS
197
Fig. 5. Amalgam filling made about 2 years before extraction of the tooth. Subgingival part of filling was completely covered with plaque and the plaque had also proliferated in apical direction from filling margin to extent indicated by arrows. Subgingival scaling carried out 5 months before extraction, demonstrating limitation of this kind of treatment when restorations are present. covered with plaque was 6 weeks (Fig. 6), and the longest period a restoration was found to be free of plaque was 2 years. The teeth, which were extracted by the author, were immediately, and without fixation, stained in toluidine blue, basic fuchsin or crystal violet. The teeth obtained from the other dentists were fixed in formalin and stained by the author. The teeth were air dried and examined under the stereomicroscope. Results
Table 1 shows that 99 out of the 108 restorations were covered with plaque; in some cases the plaque was found on top of calculus. Some photographs which illustrate typical conditions will be shown. In Fig. 4 there is a plaque-free zone on the amalgam filling below the gingival margin. Here the amalgam with a cuticle
on top of it had been in contact with the pocket epithelium (epithelial cuff), and it can safely be concluded that the inflammatory reaction in the soft tissue had been slight and of about the same severity as in Fig. 1. This filling was classified as plaque-free even if there is some subgingival plaque shortly below the gingival margin. Fig. 5 shows the mesial surface of a molar with an amalgam filling. The filling had been made about 2 years before the extraction and subgingival scaling had been carried out twice a year, the last time 5 months before extraction. If absence of subgingival plaque is taJken as evidence that a healthy epithelial cuff had reappeared in the curetted area, the healing had been p>erfect adjacent to the
198
Fig. 6. enamel surface dicated
WAERHAUG
Zinc oxide-eugenol filling placed 3 mm below gingival margin and ending at cementojunction. Filling is completely covered with plaque. Note that there is no plaque on tooth on both sides of filling. There is a loss of attachment of about 1.0 mm below filling as inwith arrows. Observation period 6 weeks.
tooth. Even a piece of calculus, C, left behind during the scaling, was free of plaque, and consequently non-irritating. However, the amalgam filling was completely covered with plaque. The plaque had even grown about half a millimeter in apical direction from the margin of the filling, as indicated with the arrows. Fig. 6 shows a temporary zinc-oxide eugenol filling which had been in place for 6 weeks. It is completely covered with plaque, and there is even a loss of attachment of about 1 mm due to the bacterial inflammation. The amalgam filling shown in Fig. 7 had, according to the patient, been made about 8 months earlier. In this study it was listed as "without plaque" because not all the subgingival part of it was cov-
Fig. 7. Amalgam filling placed about 8 months before extraction. Cervical part of filling is still plaque-free, but plaque had developed to about 1.0 mm below gingival margin. There is no plaque on subgingival part of tooth on either side of the filling.
PLAQUE ON DENTAL RESTORATIONS ered with plaque. However, it is obvious that plaque is rapidly being formed. Very few amalgam fillings had been polished. Fig. 4 had been polished and it is possible that this had contributed to the favorable restilt. In practically all cases overhangs were observed. The overhangs in Figs. 4, 5 and 7 measured 0.5, 1.2 and 1.0 mm respectively. There was always some space between the amalgam filling and the tooth, as shown in Figs. 4 and 7. What is said about the technical standard of the amalgam fillings holds true for the rest of the restorations. Between the crowns and the preparations there were always defects. Discussion
In evaluating these observations it should be kept in mind that the material is selected and that the percentage of subgingival restorations covered with plaque observed here cannot be claimed to be representative for the Norwegian population as a whole. Let us assume, and hope, that the conditions are better, but the fact still remains that a large proportion of the restorations which are placed below the gingival margin are likely to be covered with plaque within weeks, months or years. The findings made here do not allow conclusions to be drawn regarding the average time needed for plaque to cover a subgingival restoration and to what extent there are differences between the various materials and types of restorations. However, the observations that a zinc oxideeugenol filling (Fig. 6) was completely covered with plaque in 6 weeks, and that an amalgam filling (Fig. 7) was mostly covered in about 8 months, at least indicate that plaque develops fast in some cases. Indeed, this problem merits further experimental investigation. There may be several reasons wKy
199
plaque accumulates so much faster on restorations than on a plain tooth surface: (1) the surfaces of materials like cements (Fig. 1 and 6) and axnalgam (Figs. 4, 5 and 7) are rough as estimated by microbiologic standards, even if they are polished (Fig. 4), (2) spaces between restorations and preparations (Figs. 3 & 4) which may look negligible when estimated by technical standards, are likely to be very important from a microbiologic point of view. In addition, none of the restorations in this material fulfilled the requirements of technical perfectionism even when examined with the naked eye, and (3) physicochemical qualities of amalgam and cements may directly contribute to the attachment of plaque-bacteria. . In order to understand what happens in the soft tissue adjacent to a subgingival restoration it is essential to be familiar with some basic features of the healthy gingival pocket. Under physiologic conditions the dentoepithelial junction seals the hole in the epithelium created by the tooth. This epithelial cuff which clinically is the soft tissue wall of the healthy gingival pocket is a dynamic tissue. Bacteria which are brought into the pocket during clinical procedures are washed out or killed within minutes or hours, and the integrity of the dentogingival junction is reestablished. (WAERHAUG 1952). This is a highly important defense mechanism, and it appears as if a smooth tooth surface is one of the requirements for the series of reactions to take place in an adequate way. When the smooth tooth surface is replaced with a foreign body with all the above mentioned deficiencies, the defense mechanism is apparently impeded in its function and the result is rapid plaque formation. In fact, from a biologic point of view it is not surprising that such an interference takes place. When the plaque organisms have gotten
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a foothold on the filling they induce inflammation in the adjacent soft tissue and sooner or later this will lead to loss of attachment. How quickly attachment can be lost is well demonstrated in Fig. 6. Within 6 weeks the zinc oxide-eugenol filling was completely covered with plaque subgingivally, and the inflammation induced by the microorganisms had broken down the periodontal fibers to a distance of about 1 mm below the filling as indicated with the arrows. In fact, the speed of the destruction of the attachment apparatus in cases like Figs. 5 and 6 will be determined by the ability of the plaque-organisms to proliferate in apical direction from their base on the restoration. Fig. 6 represents a fairly common situation in practice. Deep approximal caries undermines the enamel and the cavity is easily extended to the bottom of the pocket which in young individuals corresponds to the cemento-enamel junction, as was the case here. The cavity may be filled with amalgam., cement or some other material, which as previously mentioned facilitates retention of bacteria. In the case of Fig. 6 this means that the filling brought the plaque to a position which was about 3 mm further apically than it was on the tooth on both sides. For the plaque to proliferate the same distance on a smooth tooth surface might take 10-30 years. This is why restorations are so relevant in the etiology of periodontal disease. Another problem created by subgingival restorations is that routine periodontal treatment such as subgingival scaling has a limited effect. At best, such treatment can prevent the plaque from spreading too far apically from the filling margin, as was attained in the case of Fig. 5. But even the most perfect subgingival scaling will not prevent rapid reformation of plaque on the filling itself as can rou-
tinely be attained on a plain tooth surface (see both sides of the filling in Fig. 5). Prevention of secondary caries by extending restorations to below the gingival margin creates periodontal problems which eventually may lead to the loss of the tooth. At a time when these consequences of subgingival restorations were unknown there was good reason to extend the filling, but with our present knowledge there is a good reason for not doing so. Fortunately there is an alternative. Recent clinical trials by AXELSSON & LINDHE (1974) have shown that both primary and secondary caries can be prevented by proper oral hygiene measures. Restorations placed below the gingival margin are likely to accumulate plaque subgingivally even if routine oral hygiene is maintained. Plaque is quickly reformed on subgingival fillings after scaling. Plaque on subgingival restorations can lead to loss of attachment.
References
P. & LINDHE, J.: The effect of a preventive programme on dental plaque, gingivitis and caries in schoolchildren. Results after one and two years. / . Clin. Feriodontol. 1974: 1: 126-138. KARLSEN, K . : Gingival reactions to dental restorations. Acta Odontol. Scand. 1970: 28: 895-904. AXELSSON,
LINDHE, J., HAMP, S. E . & LOE, H . : Experi-
mental periodontitis in the beagle dog. / . Periodontal Res. 1973: 8: 1-10. LOE, H . , THEIL.-VDE, E . & JENSEN, S. B.: Experimental gingivitis in man. / . Periodontol. 1965: 36: 177-187. SILNESS, J.: Periodontal conditions in patients treated with dental bridges. / . Periodontal Res. 1970: 5: 60-68. SILNESS, J.: Periodontal conditions in patients treated with dental bridges. II. The infiuence of full and partial crowns on plaque accumulation, development of gingivitis and pocket formation. / . Periodontal Res. 1970: 5: 219224.
PLAQUE ON DENTAL RESTORATIONS J.: Periodontal conditions in patients treated with dental bridges. III. The relationship between the location of the crown margin and the periodontal condition. /. Periodontal Res. 1970: 5: 225-229. SILNESS, J.: Periodontal conditions in patients treated with dental bridges. V. Effect of splinting of adjacent abutment teeth. /. Periodontal Res. 1974: 9: 121-126. WAERHAUG, J . : The gingival pocket. Anatomy, pathology, deepening and elimination. Thesis. Odontol. Tidskr. 1952: 80: Suppl. 1. WAERHAUG, J.: Tissue reaction around artificial crowns. / . Periodontol. 1953: 24: 172-185. WAERHAUG, J.: Effect of zinc phosphate cement fillings on gingival tissues. ./. Periodontol. 1956: 27: 284-290. WAERHAUG, J.: Observations on extracted i:eeth plated with gold foil. Oral Surg. 1956: 9: 780-791. WAERHAUG, J. & ZANDER, H . A.: Reaction of gingival tissues to selfcuring acrylic restorations. /. Am. Dent. Assoc. 1957: 54: 760768. SILNESS,
Address: Department of Periodonties Faculty of Dentistry 69 Geitmyrsveien Oslo 3 Norway
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J.: Tissue reactions around acrylic root tips. /. Dent. Res. 1957: 36: 27-38. WAERHAUG, J.: Histologic considerations which govern where the margins of restorations should be located in /elation to the gingiva. Dent. Clin. North Am. 1960: 161-176. WAERHAUG, J.: Dental restorations as cause of periodontal destruction. Audiovisual program (53 slides). Department of Periodonties, University of Oslo. Oslo 1972. Available on request. WAERHAUG, J.: A method for the evaluation of periodontal problems on extracted teeth. Audiovisual program (29 slides). Department of Periodonties, University of Oslo, Oslo 1973. Available on request. WAERHAUG, J.: A method for evaluation of periodontal problems on extracted teeth. /. Clin. Periodontol. 1975: 2: in press. ZANDER, H . A.: Effect of silicate cement and amalgam on the gingiva. /. Am. Dent. Assoc. 1957: 55: 11-15. WAERHAUG,
