0099-2399/90/1611-0523/$02.00/0 JOURNAL OF ENDODONTtCS Copyright 9 1990 by The American Association of Endodontists
Printed in U.S.A.
VOL. 16, No, 11, NOVEMBER1990
A Comparative In Vitro Coronal Microleakage Study of New Endodontic Restorative Materials Angela P. Noguera, DDS, MS, and N. J. McDonald, BDS, MS
qualities of temporary filling material are of primary importance in endodontic therapy. Although there are numerous techniques for measuring microleakage, the necessity for simulating intraoral temperature change is important. The oral cavity is subject to significant changes in temperature, and this factor perhaps is the leading etiology for leakage; therefore, the necessity for simulating these temperature changes must be addressed in any microleakage study (11-14). In the past the use of Cavit (ESPE, Seefeld/Oberbay, West Germany), a calcium sulfatepolyvinyl chloride acetate, and IRM (L. D. Caulk Co., Milford, DE), a formulation based on zinc oxide-eugenol reinforced polystyrene beads, had been advocated by many authors (15-17). Recently, new temporary filling materials TERM (L. D. Caulk Co.) and Dentemp (Majestic Drug Co., Bronx, NY) have become commercially available. Dentemp, like IRM, is a zinc oxide-eugenol-based material but lacks reinforcement. TERM (Temporary Endodontic Restorative Material) is a composite-like product whose principal component is urethane dimethacrylate polymer. With the advent of these new temporary filling materials and the sparcity of comparative in vitro marginal leakage studies, it was the purpose of this in vitro study to compare the sealing ability of Cavit, Cavit-G, Cavit-W, and 1RM-Caps (L. D. Caulk Co.) with TERM, Hard-TERM (an experimental formulation of TERM), and Dentemp.
Complete sealing of endodontic access openings between appointments and after completion of therapy is an essential element in achieving endodontic success. Recently, two new products for use as temporary restorative materials, TERM and Dentemp, have become available. The purpose of this study was to compare in vitro the sealing ability of Cavit, Cavit-G, Cavit-W, and IRM-Caps, with TERM, Hard-TERM, and Dentemp. Standard access cavities were prepared in 144 intact extracted human teeth. They were equally and randomly distributed into seven groups, and their access openings were temporized. Specimens were submitted to thermocycling (5 to 55~ for 7 days and stained with silver nitrate. The teeth were split in half, and the greatest depth of dye penetration at the tooth surface was recorded. TERM exhibited the least leakage, while Hard-TERM demonstrated the greatest leakage, at the tooth-restoration interface.
During endodontic therapy, it is important to create a fluidtight seal in the access cavity in order to prevent marginal leakage and the ingress of oral fluids and microorganisms into the root canal. There have been numerous studies related to the subject of marginal leakage around dental restorations. Techniques to assess marginal leakage include the use of dyes, radiolabeled ions, bacteria, air under pressure, and variations in temperature (1-5). All of these studies emphasize the fact that the margins of restorations are not closed but rather, as Myers (6) stated, are " . . . dynamic microcrevices which contain a busy traffic of ions and molecules." Although there are many bonding materials available, the most commonly used intermediate restorative materials do not possess adherent properties. Numerous studies to determine the extent of leakage at the tooth-restoration interface with these materials have been undertaken (7-9). According to Weine (10), the function of a temporary filling material in endodontics is 2-fold" first, to prevent saliva and microorganisms from gaining entrance into the root canal, thus preventing infection or reinfection, and, second, to prevent medicaments placed into the pulp chamber from escaping into the oral cavity. If Weine's criteria are to be met, the sealing
MATERIALS AND METHODS One-hundred forty-four intact, freshly extracted maxillary and mandibular posterior human teeth were used. Immediately after extraction, all teeth were kept in 0.9% sodium chloride (Travenol Laboratories Inc., Deerfield, IL) to avoid dehydration. The intermediate restorative materials selected for this study were IRM-Caps, Cavit, Cavit-G, Cavit-W, TERM, Hard-TERM, and Dentemp. The teeth were randomly divided into seven groups of 20 teeth each. Each group was treated with one of the aforementioned materials, following the manufacturer's instructions. Each tooth was identically prepared to receive the temporary material, as follows. The occlusal surface was ground flat using a regular plaster trimmer (model trimmer; Handler Mfg Co., Westfield, N J), and the roots were cut at the furcation level with the use of a diamond wheel (Dayton Electric Mfg Co., Chicago, IL). A 4.0- x 4.0-mm standardized access cavity
523
524
Noguera and McDonald
was designed on a template and drawn on the occlusal surface with a black pencil. In order to cover all exposed dentinal tubules, the occlusal surface was painted with clear nail polish, and the root surface was coated once with colored nail polish. Both were allowed to dry for 30 min at room temperature. The teeth were submerged twice in melted wax to the level of the cementodentinal junction to ensure an apical seal. The root surfaces of each group were coated with a different color nail polish, so that all of the samples could go through the thermocycling bath simultaneously and still be recognized for statistical evaluation. Access cavities were prepared under water spray at ultra high-speed with a #4 round carbide bur and finally defined to the designed occlusal outline with a #700 carbide bur (Midwest-Sybron, Des Plains, IL). Each cavity was air dried, and a dry #3 cotton pellet was placed on the floor of the pulp chamber. The depth of the cavity was measured with a periodontal probe. All samples allowed for at least 5 m m of temporary material to be placed into the access opening. The intermediate restorative materials were placed following the respective manufacturers' instructions. Dentemp, a premeasured powder/liquid product, was mixed to a puttylike consistency, dried three to four times in a clean tissue to absorb the excess eugenol, and air dried for 10 min until it exhibited a slightly tacky consistency. It was then rolled into a ball and placed into the access cavity with finger pressure. IRM-Caps, supplied in a premeasured capsule, was activated and mixed in a Wig L Bug amalgamator for 12 s and finally placed into the cavity with a Glick plastic instrument. TERM and Hard-TERM were provided in ampules for direct injection into the access cavities. The material was adapted, carved, and finally subjected to a visible light for 40 s. All products were prepared and placed in the access cavities by the senior author, except for Dentemp, which was mixed and placed by an individual, blind to the experimental design, in order to avoid the possibility of bias during the spatulation and placement of the material. After the access cavities were filled, the specimens were immediately placed in saline for 2 h at 37~ to ensure setting of the material. Using a maximum temperature of 55~ and a low of 5~ teeth were then placed in a thermocycling bath (2095 Bath & Circulator; Forma Scientific, Marietta, OH) for 7 days. These high and low values were obtained by measuring the temperature of a hot cup of coffee and of ice water. Using cycles of 90- and 30-s dwell times in each bath, specimens were subjected to a total of 6720 cycles. After the samples were removed from the thermocycling bath, they were simultaneously submerged in 50% by weight AgNO3 for 2 h, rinsed in distilled water for 1 min, and placed in Quick Developer (M & D International, Carpenteria, CA) for 1 h. All teeth were then air dried and grooved on the mesial and distal surfaces with the use of a diamond wheel. Using pliers, all samples were split through their longitudinal axis, and the coronal linear depth o f dye penetration was measured in millimeters on the tooth surface using a calibrated stereomicroscope (Gaertner Optics, Chicago, IL). The two positive controls received the exact same treatment as described above, except no temporary material was placed in the access openings. The two negative controls did not have access cavities cut; their entire occlusal surface was covered with clear nail polish, and their roots were covered with colored nail polish and dipped twice in melted wax.
Journal of Endodontics
The greatest depth of dye penetration along the wall of the access cavity was recorded for each specimen at two separate times by the same examiner. Reliability of the recorded data was tested with a correlation coefficient test. Because of the parametric nature of the data, an analysis of variance and Duncan's multiple range test were applied.
RESULTS The mean leakage values in millimeters for each group are presented in Fig. 1. No samples were lost during the study. The positive control teeth (Fig. 2A) showed 100% staining with silver nitrate from the most coronal point of the access cavities to the most apical location of the access. The negative control group teeth (Fig. 2B) did not show any sign of coronal microleakage. A one-way analysis of variance was performed to determine the presence of significant differences between the means of each group; the results are presented in Table 1. A statistically significant F ratio o f 33.80 (p < 0.0001) was obtained, and a Duncan's multiple range test was run in order to ascertain which groups were significantly different from the others. The results are shown in Fig. 1. Bartlett's test for the homogenity of variance was applied to the data; its result was nonsignificant. TERM (Fig. 3A) had the lowest mean leakage value of 0.92 + 0.67 mm, showing a statistically significant difference between this value and those o f Hard-TERM, Cavit, Cavit-G, Cavit-W, IRM-Caps, and Dentemp. Through the Duncan's multiple range test, T E R M was classified as subset I. Subset II (Cavit, Cavit-G, and Cavit-W) (Fig. 4) showed mean leakage values and standard deviations of 1.52 - 0.48, 1.58 --- 0.67, and 1.38 _+ 0.58 mm, respectively. Although no significant differences among the Cavit groups were found, subset II was statistically different from TERM, Hard-TERM, IRM-Caps, and Dentemp. Subset III, IRM-Caps (Fig. 5A) and Dentemp (Fig. 5B), had mean leakage values and standard deviations of 2.42 _ 0.59 and 2.34 _ 0.78 mm, respectively. There was not a statistically significant difference between IRM-Caps and Dentemp, but these values showed a significant difference when compared with those of the Cavit, Cavit-G, Cavit-W, Hard-TERM, and T E R M groups. Subset IV, Hard-TERM (Fig. 3B), presented the poorest sealing ability at the tooth-restoration interface. It exhibited the highest mean leakage value of 3.56 _ 0.90 mm, which was significantly different when compared with all of the other tested materials. During the recording of leakage values, it was noted that all products presented some dye penetration through the material. The mean value of the depth of temporary filling material and the mean leakage value within the material were recorded. In order to ascertain whether a correlation existed between this data and the amount of leakage at the toothrestoration interface, a correlation coefficient test was run. These results are presented in Table 2. No statistically significant difference (p < 0.001 ) was found between the depth of the material and the route of leakage. Cavit-W demonstrated the lowest mean leakage value, 0.20 mm, within the material itself, while Cavit and Dentemp had the highest values of 1.53 m m and 1.24 ram, respectively. All
Vol. 16, No. 11, November 1990
Endodontic Restorative Materials
525
DEPTH OF PENETRATION (MM)
0.
TERM
Cavit
Cavit-G
Cavit-W IRM-Caps Dememp
tI-TIiRM
FIG 1. Mean leakage of the experimental groups. TABLE 1. Analysis of variance Source
df
SS
Between Within
6 133
93.09 61.07
Total
139
154.15
MS
F
15.51 0.56
33.79*
9 ~ < 0.001.
FiG 2. A, Positive. B, Negative controls.
of the materials leaked more at the tooth-restoration interface, as compared with leakage through the bulk of the material, except for Cavit, which leaked 1.52 m m at the interface and 1.53 through itself. The depth of material was found to be very constant in all of the groups except for Dentemp, whose 3.91-mm value was significantly less, even though there was at least 5 m m of space allowed for the material to be placed.
FIG 3. TERM and Hard-TERM restorations demonstrating the minimum and maximum leakage values (arrows).
DISCUSSION The results o f this in vitro study indicate that T E R M provides a better coronal marginal seal in standardized access preparations than do Cavit, Cavit-G, Cavit-W, Dentemp, IRM-Caps, or Hard-TERM. Inspection of the raw data, as measured by the silver stain technique, indicates that all samples leaked to some extent at the tooth-restoration inter-
face. One reason for this phenomenon was probably a variation in the linear coefficients of thermal expansion between the materials tested, as there is a direct relationship between the coefficient of thermal expansion and degree of microleakage (18). Even though chemically, there is not a significant difference between TERM and H a r d - T E R M (the two materials that generated the m i n i m u m and maximum leakage
526
Noguera and McDonald
Journal of Endodontics
FIG 4. A, IRM-Caps and Dentemp restorations demonstrating leakage
(arrows).
FIG 5. Cavit-W exhibiting leakage
(arrows).
TABLE 2. Depth of temporary filling material and mean leakage values within the material itself in correlation with the mean leakage values at the tooth-restoration interface Mean Values Group Hard-TERM TERM Cavit Cavit-G Cavit-W IRM-Caps Dentemp
Depth of Material
Interface
Within*
5.85 5.34 5.23 5.50 4.90 5.61 3.91
3.56 0.93 1.52 1.58 1.38 2.42 2.34
0.22 0.40 1.53 0.42 0.20 0.69 1.24
9p < 0.001.
values, respectively), it is possible that the difference in the amount and type of filler in TERM and Hard-TERM is sufficient to produce a significant alteration in the coefficient of thermal expansion. All of the groups demonstrated leakage within the material. The material exhibiting the greatest value was Cavit followed by Dentemp. This may be due to the increased water sorption values of the calcium sulfate-based materials and, to a lesser extent, that of the zinc oxide-eugenol-based materials (16, 17). Only one sample from the Cavit-G group did not exhibit any leakage through the material itself.
Cavit is a moisture-initiated, autopolymerized, premixed calcium sulfate-polyvinyl chloride acetate, temporary restorative material, which is widely used between appointments during routine endodontic therapy, probably because of its practical "ready to use" condition (19). One of the major disadvantages of Cavit, besides its reduced strength, is its slow setting time. The expansion of the material against the cavity during the setting phase is believed to be responsible for the adequate seal provided by Cavit (11). Conversely, TERM does not require an aqueous environment to initiate its setting reaction; instead, it is initiated by exposure to a visible light source for 40 s. This property enables TERM to be placed, carved, and set, offering no postoperative delays in order to achieve maximum function. IRM-Caps is provided in capsules, which grant a "puttylike" consistency when amalgamated correctly. Dentemp, conversely, offers only the convenience of being available "over the counter." The mean depth of Dentemp, 3.91 m m (Table 2), was significantly lower than the average, even though there was enough space for the material to be placed. Extreme care was taken to follow the manufacturer's instructions, but the final preparation was too runny and messy, making it very difficult to handle. Silver nitrate was used as an indicator of microleakage in this study because it provides a well-defined and visible method, with an excellent color contrast for tracing the extent of penetration (9). Webber et al. (20) recommended that a minimum depth of 3.5 m m of Cavit be placed to prevent leakage. The findings in this study suggest that an average of 3.0 m m of Cavit, when used as a temporary sealing material, may be sufficient to offer good sealing conditions between endodontic appointments. It is suggested that Cavit be used as a temporary filling material until more information evaluating the physical and mechanical properties of TERM, as a function of time, are available. Dr. Noguera is a former postgraduate endedontic resident, Department of Endodontics, Baltimore College of Dental Surgery, Dental School, University of Maryland at Baltimore, Baltimore, MD. Dr. McDonald is clinical instructor, Department of Endodontics, Baltimore College of Dental Surgery, Dental School, University of Maryland at Baltimore.
References 1. Grossman LI. Study of temporary fillings as hermetic sealing agents. J Dent Res 1939;18:67-71. 2. Friedman S, Shani J, Stabholz A, Kaplawi J. Comparative sealing ability of temporary filling materials evaluated by leakage of radiosodium. Int Endod J 1986;19:187-93. 3. Seltzer S. The penetration of microorganisms between the tooth and direct resin fillings. J Am Dent Assoc 1955;57:560. 4. Nelsen RJ, Wolcott RB, Paffenbarger GC. Fluid exchange at the margins of dental restorations. J Am Dent Assoc 1952;44:288. 5. Crim GA, Swartz ML, Phillips RW. Comparison of four thermocycling techniques. J Prosthet Dent 1985;53:50-3. 6. Myers HM. The scientific bases of dentistry. In: Shapiro M, ed. Philadelphia: WB Saunders, 1966:285. 7. Marosky JE, Patterson SS, Swartz M. Marginal leakage of temporary sealing materials used between endodontic appointments and assessed by calcium 45--an in vitro study. J Endodon 1977;3:110-3. 8. Swanson K, Madison S. An evaluation of coronal microleakage in endodontically treated teeth. Part I. Time pedods. J Endodon 1987;13:56-9. 9. Dumsha TC, Biron G. Inhibition of marginal leakage with a dentin bonding agent. J Dent Res 1984;63:1255-7. 10. Weine FS. Endodotic therapy. St. Louis: CV Mosby, 1976.
Vol. 16, No. 11, November 1990 11. Gilles JA, Huget EF, Stone RC. Dimensional stability of temporary restoratives. Oral Surg 1975;40:796-800. 12. Crim GA, Mattingly SL. Evaluation for two methods for assessing marginal leakage. J Prosthet Dent 1981 ;45:160-3. 13. Pards L, Kapsimalis P. The effect of temperature change on the sealing properties of temporary filling materials. Part I. Oral Surg 1960;13:982-9. 14. Oppenheimer S, Rosenberg P, Effect of temperature change on the sealing properties of Cavit and Cavit G. Oral Surg 1979;48:250-3. 15. Orahood JP, Cochran MA, Swartz M, Newton C. In vitro study of marginal leakage between temporary sealing materials and recently placed restorative materials. J Endodon 1986;12:523-7.
Endodontic Restorative Materials
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16. Bennett RJ. Physical properties and microleakage evaluation of a new temporary endodontic filling material TERM | [Abstract 1517]. J Dent Res 1987;66:296. 17. Widerman FH, Eames WB, Serene TP. The physical and biologic properties of Cavit. J Am Dent Assoc 1971 ;82:378-82. 18. Bullard RH, Leinfelder KF, Russell CM. Effect of coefficient of thermal expansion on microleakage. J Am Dent Assoc 1988;116:871-4. 19. Ingle JI, Beveridge EE. Endodontics. 2nd ed. Philadelphia: Lea & Febiger, 1976:88. 20. Webber RT, del Rio CE, Brady JM, Segall RO. Sealing quality of a temporary filling material. Oral Surg 1978;46:123-30.
Printed in U.S.A.
VOL. 16, No, 11, NOVEMBER1990
A Comparative In Vitro Coronal Microleakage Study of New Endodontic Restorative Materials Angela P. Noguera, DDS, MS, and N. J. McDonald, BDS, MS
qualities of temporary filling material are of primary importance in endodontic therapy. Although there are numerous techniques for measuring microleakage, the necessity for simulating intraoral temperature change is important. The oral cavity is subject to significant changes in temperature, and this factor perhaps is the leading etiology for leakage; therefore, the necessity for simulating these temperature changes must be addressed in any microleakage study (11-14). In the past the use of Cavit (ESPE, Seefeld/Oberbay, West Germany), a calcium sulfatepolyvinyl chloride acetate, and IRM (L. D. Caulk Co., Milford, DE), a formulation based on zinc oxide-eugenol reinforced polystyrene beads, had been advocated by many authors (15-17). Recently, new temporary filling materials TERM (L. D. Caulk Co.) and Dentemp (Majestic Drug Co., Bronx, NY) have become commercially available. Dentemp, like IRM, is a zinc oxide-eugenol-based material but lacks reinforcement. TERM (Temporary Endodontic Restorative Material) is a composite-like product whose principal component is urethane dimethacrylate polymer. With the advent of these new temporary filling materials and the sparcity of comparative in vitro marginal leakage studies, it was the purpose of this in vitro study to compare the sealing ability of Cavit, Cavit-G, Cavit-W, and 1RM-Caps (L. D. Caulk Co.) with TERM, Hard-TERM (an experimental formulation of TERM), and Dentemp.
Complete sealing of endodontic access openings between appointments and after completion of therapy is an essential element in achieving endodontic success. Recently, two new products for use as temporary restorative materials, TERM and Dentemp, have become available. The purpose of this study was to compare in vitro the sealing ability of Cavit, Cavit-G, Cavit-W, and IRM-Caps, with TERM, Hard-TERM, and Dentemp. Standard access cavities were prepared in 144 intact extracted human teeth. They were equally and randomly distributed into seven groups, and their access openings were temporized. Specimens were submitted to thermocycling (5 to 55~ for 7 days and stained with silver nitrate. The teeth were split in half, and the greatest depth of dye penetration at the tooth surface was recorded. TERM exhibited the least leakage, while Hard-TERM demonstrated the greatest leakage, at the tooth-restoration interface.
During endodontic therapy, it is important to create a fluidtight seal in the access cavity in order to prevent marginal leakage and the ingress of oral fluids and microorganisms into the root canal. There have been numerous studies related to the subject of marginal leakage around dental restorations. Techniques to assess marginal leakage include the use of dyes, radiolabeled ions, bacteria, air under pressure, and variations in temperature (1-5). All of these studies emphasize the fact that the margins of restorations are not closed but rather, as Myers (6) stated, are " . . . dynamic microcrevices which contain a busy traffic of ions and molecules." Although there are many bonding materials available, the most commonly used intermediate restorative materials do not possess adherent properties. Numerous studies to determine the extent of leakage at the tooth-restoration interface with these materials have been undertaken (7-9). According to Weine (10), the function of a temporary filling material in endodontics is 2-fold" first, to prevent saliva and microorganisms from gaining entrance into the root canal, thus preventing infection or reinfection, and, second, to prevent medicaments placed into the pulp chamber from escaping into the oral cavity. If Weine's criteria are to be met, the sealing
MATERIALS AND METHODS One-hundred forty-four intact, freshly extracted maxillary and mandibular posterior human teeth were used. Immediately after extraction, all teeth were kept in 0.9% sodium chloride (Travenol Laboratories Inc., Deerfield, IL) to avoid dehydration. The intermediate restorative materials selected for this study were IRM-Caps, Cavit, Cavit-G, Cavit-W, TERM, Hard-TERM, and Dentemp. The teeth were randomly divided into seven groups of 20 teeth each. Each group was treated with one of the aforementioned materials, following the manufacturer's instructions. Each tooth was identically prepared to receive the temporary material, as follows. The occlusal surface was ground flat using a regular plaster trimmer (model trimmer; Handler Mfg Co., Westfield, N J), and the roots were cut at the furcation level with the use of a diamond wheel (Dayton Electric Mfg Co., Chicago, IL). A 4.0- x 4.0-mm standardized access cavity
523
524
Noguera and McDonald
was designed on a template and drawn on the occlusal surface with a black pencil. In order to cover all exposed dentinal tubules, the occlusal surface was painted with clear nail polish, and the root surface was coated once with colored nail polish. Both were allowed to dry for 30 min at room temperature. The teeth were submerged twice in melted wax to the level of the cementodentinal junction to ensure an apical seal. The root surfaces of each group were coated with a different color nail polish, so that all of the samples could go through the thermocycling bath simultaneously and still be recognized for statistical evaluation. Access cavities were prepared under water spray at ultra high-speed with a #4 round carbide bur and finally defined to the designed occlusal outline with a #700 carbide bur (Midwest-Sybron, Des Plains, IL). Each cavity was air dried, and a dry #3 cotton pellet was placed on the floor of the pulp chamber. The depth of the cavity was measured with a periodontal probe. All samples allowed for at least 5 m m of temporary material to be placed into the access opening. The intermediate restorative materials were placed following the respective manufacturers' instructions. Dentemp, a premeasured powder/liquid product, was mixed to a puttylike consistency, dried three to four times in a clean tissue to absorb the excess eugenol, and air dried for 10 min until it exhibited a slightly tacky consistency. It was then rolled into a ball and placed into the access cavity with finger pressure. IRM-Caps, supplied in a premeasured capsule, was activated and mixed in a Wig L Bug amalgamator for 12 s and finally placed into the cavity with a Glick plastic instrument. TERM and Hard-TERM were provided in ampules for direct injection into the access cavities. The material was adapted, carved, and finally subjected to a visible light for 40 s. All products were prepared and placed in the access cavities by the senior author, except for Dentemp, which was mixed and placed by an individual, blind to the experimental design, in order to avoid the possibility of bias during the spatulation and placement of the material. After the access cavities were filled, the specimens were immediately placed in saline for 2 h at 37~ to ensure setting of the material. Using a maximum temperature of 55~ and a low of 5~ teeth were then placed in a thermocycling bath (2095 Bath & Circulator; Forma Scientific, Marietta, OH) for 7 days. These high and low values were obtained by measuring the temperature of a hot cup of coffee and of ice water. Using cycles of 90- and 30-s dwell times in each bath, specimens were subjected to a total of 6720 cycles. After the samples were removed from the thermocycling bath, they were simultaneously submerged in 50% by weight AgNO3 for 2 h, rinsed in distilled water for 1 min, and placed in Quick Developer (M & D International, Carpenteria, CA) for 1 h. All teeth were then air dried and grooved on the mesial and distal surfaces with the use of a diamond wheel. Using pliers, all samples were split through their longitudinal axis, and the coronal linear depth o f dye penetration was measured in millimeters on the tooth surface using a calibrated stereomicroscope (Gaertner Optics, Chicago, IL). The two positive controls received the exact same treatment as described above, except no temporary material was placed in the access openings. The two negative controls did not have access cavities cut; their entire occlusal surface was covered with clear nail polish, and their roots were covered with colored nail polish and dipped twice in melted wax.
Journal of Endodontics
The greatest depth of dye penetration along the wall of the access cavity was recorded for each specimen at two separate times by the same examiner. Reliability of the recorded data was tested with a correlation coefficient test. Because of the parametric nature of the data, an analysis of variance and Duncan's multiple range test were applied.
RESULTS The mean leakage values in millimeters for each group are presented in Fig. 1. No samples were lost during the study. The positive control teeth (Fig. 2A) showed 100% staining with silver nitrate from the most coronal point of the access cavities to the most apical location of the access. The negative control group teeth (Fig. 2B) did not show any sign of coronal microleakage. A one-way analysis of variance was performed to determine the presence of significant differences between the means of each group; the results are presented in Table 1. A statistically significant F ratio o f 33.80 (p < 0.0001) was obtained, and a Duncan's multiple range test was run in order to ascertain which groups were significantly different from the others. The results are shown in Fig. 1. Bartlett's test for the homogenity of variance was applied to the data; its result was nonsignificant. TERM (Fig. 3A) had the lowest mean leakage value of 0.92 + 0.67 mm, showing a statistically significant difference between this value and those o f Hard-TERM, Cavit, Cavit-G, Cavit-W, IRM-Caps, and Dentemp. Through the Duncan's multiple range test, T E R M was classified as subset I. Subset II (Cavit, Cavit-G, and Cavit-W) (Fig. 4) showed mean leakage values and standard deviations of 1.52 - 0.48, 1.58 --- 0.67, and 1.38 _+ 0.58 mm, respectively. Although no significant differences among the Cavit groups were found, subset II was statistically different from TERM, Hard-TERM, IRM-Caps, and Dentemp. Subset III, IRM-Caps (Fig. 5A) and Dentemp (Fig. 5B), had mean leakage values and standard deviations of 2.42 _ 0.59 and 2.34 _ 0.78 mm, respectively. There was not a statistically significant difference between IRM-Caps and Dentemp, but these values showed a significant difference when compared with those of the Cavit, Cavit-G, Cavit-W, Hard-TERM, and T E R M groups. Subset IV, Hard-TERM (Fig. 3B), presented the poorest sealing ability at the tooth-restoration interface. It exhibited the highest mean leakage value of 3.56 _ 0.90 mm, which was significantly different when compared with all of the other tested materials. During the recording of leakage values, it was noted that all products presented some dye penetration through the material. The mean value of the depth of temporary filling material and the mean leakage value within the material were recorded. In order to ascertain whether a correlation existed between this data and the amount of leakage at the toothrestoration interface, a correlation coefficient test was run. These results are presented in Table 2. No statistically significant difference (p < 0.001 ) was found between the depth of the material and the route of leakage. Cavit-W demonstrated the lowest mean leakage value, 0.20 mm, within the material itself, while Cavit and Dentemp had the highest values of 1.53 m m and 1.24 ram, respectively. All
Vol. 16, No. 11, November 1990
Endodontic Restorative Materials
525
DEPTH OF PENETRATION (MM)
0.
TERM
Cavit
Cavit-G
Cavit-W IRM-Caps Dememp
tI-TIiRM
FIG 1. Mean leakage of the experimental groups. TABLE 1. Analysis of variance Source
df
SS
Between Within
6 133
93.09 61.07
Total
139
154.15
MS
F
15.51 0.56
33.79*
9 ~ < 0.001.
FiG 2. A, Positive. B, Negative controls.
of the materials leaked more at the tooth-restoration interface, as compared with leakage through the bulk of the material, except for Cavit, which leaked 1.52 m m at the interface and 1.53 through itself. The depth of material was found to be very constant in all of the groups except for Dentemp, whose 3.91-mm value was significantly less, even though there was at least 5 m m of space allowed for the material to be placed.
FIG 3. TERM and Hard-TERM restorations demonstrating the minimum and maximum leakage values (arrows).
DISCUSSION The results o f this in vitro study indicate that T E R M provides a better coronal marginal seal in standardized access preparations than do Cavit, Cavit-G, Cavit-W, Dentemp, IRM-Caps, or Hard-TERM. Inspection of the raw data, as measured by the silver stain technique, indicates that all samples leaked to some extent at the tooth-restoration inter-
face. One reason for this phenomenon was probably a variation in the linear coefficients of thermal expansion between the materials tested, as there is a direct relationship between the coefficient of thermal expansion and degree of microleakage (18). Even though chemically, there is not a significant difference between TERM and H a r d - T E R M (the two materials that generated the m i n i m u m and maximum leakage
526
Noguera and McDonald
Journal of Endodontics
FIG 4. A, IRM-Caps and Dentemp restorations demonstrating leakage
(arrows).
FIG 5. Cavit-W exhibiting leakage
(arrows).
TABLE 2. Depth of temporary filling material and mean leakage values within the material itself in correlation with the mean leakage values at the tooth-restoration interface Mean Values Group Hard-TERM TERM Cavit Cavit-G Cavit-W IRM-Caps Dentemp
Depth of Material
Interface
Within*
5.85 5.34 5.23 5.50 4.90 5.61 3.91
3.56 0.93 1.52 1.58 1.38 2.42 2.34
0.22 0.40 1.53 0.42 0.20 0.69 1.24
9p < 0.001.
values, respectively), it is possible that the difference in the amount and type of filler in TERM and Hard-TERM is sufficient to produce a significant alteration in the coefficient of thermal expansion. All of the groups demonstrated leakage within the material. The material exhibiting the greatest value was Cavit followed by Dentemp. This may be due to the increased water sorption values of the calcium sulfate-based materials and, to a lesser extent, that of the zinc oxide-eugenol-based materials (16, 17). Only one sample from the Cavit-G group did not exhibit any leakage through the material itself.
Cavit is a moisture-initiated, autopolymerized, premixed calcium sulfate-polyvinyl chloride acetate, temporary restorative material, which is widely used between appointments during routine endodontic therapy, probably because of its practical "ready to use" condition (19). One of the major disadvantages of Cavit, besides its reduced strength, is its slow setting time. The expansion of the material against the cavity during the setting phase is believed to be responsible for the adequate seal provided by Cavit (11). Conversely, TERM does not require an aqueous environment to initiate its setting reaction; instead, it is initiated by exposure to a visible light source for 40 s. This property enables TERM to be placed, carved, and set, offering no postoperative delays in order to achieve maximum function. IRM-Caps is provided in capsules, which grant a "puttylike" consistency when amalgamated correctly. Dentemp, conversely, offers only the convenience of being available "over the counter." The mean depth of Dentemp, 3.91 m m (Table 2), was significantly lower than the average, even though there was enough space for the material to be placed. Extreme care was taken to follow the manufacturer's instructions, but the final preparation was too runny and messy, making it very difficult to handle. Silver nitrate was used as an indicator of microleakage in this study because it provides a well-defined and visible method, with an excellent color contrast for tracing the extent of penetration (9). Webber et al. (20) recommended that a minimum depth of 3.5 m m of Cavit be placed to prevent leakage. The findings in this study suggest that an average of 3.0 m m of Cavit, when used as a temporary sealing material, may be sufficient to offer good sealing conditions between endodontic appointments. It is suggested that Cavit be used as a temporary filling material until more information evaluating the physical and mechanical properties of TERM, as a function of time, are available. Dr. Noguera is a former postgraduate endedontic resident, Department of Endodontics, Baltimore College of Dental Surgery, Dental School, University of Maryland at Baltimore, Baltimore, MD. Dr. McDonald is clinical instructor, Department of Endodontics, Baltimore College of Dental Surgery, Dental School, University of Maryland at Baltimore.
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