0099-2399/90/1601-0001/$02 00/0 JOURNAL OF ENDODON]'ICS Copyright 9 1990 by The American Association of Endodontists
Printed in US.A. VOL. 16, NO. 1, JANUARY 1990
SCIENTIFIC ARTICLES Microleakage of Temporary Endodontic Restorations in Teeth Restored with Amalgam Jeffery E. Tumer, DMD, Ronald W. Anderson, DDS, MS, David H. Pashley, DMD, PhD, and Eugene A. Pantera, Jr., DDS, MS
Microleakage of seven temporary restorative materials was evaluated in endodontic access preparations made in teeth restored with amalgam. Ten teeth were used for each of the seven materials: Cavit, Cavit-G, TERM, zinc phosphate cement, polycarboxylate cement, glass ionomer cement, and IRM. A class I amalgam was placed in the occlusal surface of each experimental tooth and an endodontic access preparation was made entirely within the amalgam. Then the access preparation was restored with one of the temporary restorative materials, and microleakage was evaluated using a fluid filtration technique. The amount of microleakage was quantitated by measuring the fluid flow at 15 min, 1 h, 24 h, 1 wk, and 2 wk after insertion of the temporary restoration. Cavit, Cavit-G, TERM, IRM, and glass ionomer cement all provided excellent seals while zinc phosphate cement and polycarboxylate cement provided less effective seals.
An important consideration in endodontic therapy is the seal formed by the temporary restoration placed in the access preparation of a tooth undergoing treatment. Temporary restorations prevent contamination of the root canal system by oral fluids or food debris and prevent leakage of intracanal medicaments into the oral cavity. It has been shown that bacterial infection of the root canal system can lead to inflammation of the pulpal and periapical tissues (1). Temporary restorations are also important in preventing contamination of the completed root canal filling between obturation and the placement of the permanent restoration (2). This potential for contamination is directly related to the sealing ability of the temporary restorative material used. Microleakage between the temporary restoration and the walls of the access preparation has been evaluated in several investigations including studies of penetration of dye (3-5), bacteria (6-8), or radioisotopes (9-1 I) and by scanning electron microscopy (12). Previous studies report conflicting find-
ings on the sealing abilities of various materials. In bacterial studies, Krakow et al. (6) found that zinc phosphate cement and zinc oxide and eugenol (ZOE) sealed better than Cavit, whereas Blaney et al. (7) and Keller et al. (8) found that Cavit and ZOE both leaked. In contrast Parris el al. (4) reported that neither ZOE nor Cavit showed any leakage. In radioisotope studies, Friedman et al. (9) found ZOE and IRM to have less microleakage than Cavit and Marosky et al. (I0) found Cavit to provide the best seal, while Todd and Harrison (11) demonstrated that Cavit and ZOE leaked. After evaluating dye studies, Tamse et al. (5) reported that Cavit and ZOE both leaked, and Chohayeb and Bassiouny (3) found ZOE leaked but Cavit did not leak. The aforementioned studies demonstrate the great variability in results despite similar methods of investigation. The diffusion of isotopes into a canal system is greatly dependent upon the size of the molecule. Matloff et al. (13) found that dye penetrated farther into the tooth than did isotopes. They postulated that the isotope was being removed from the fluid and that the fluid may actually penetrate much farther than the isotope. Measurements from dye and isotope studies are difficult to quantitate and interpretation of the data can be subjective ( 13-15). Recently a new technique for measuring microleakage was introduced by Derkson et al. (16). This technique uses a dyecontaining liquid forced under pressure through the dentin and around the margins of restorations placed in extracted teeth. Although this technique was used to measure the microleakage of permanent restorative materials, an adaptation proved effective in quantitatively measuring microleakage of endodontic temporary restorative materials (17). Advantages of this technique are that the amount of microleakage can be quantitated, and it is not necessary to section a tooth to make measurements. Thus, longitudinal study on the same specimens is possible and the site of microleakage can be easily visualized and photographed. Previous studies evaluated the seal oftemporary restorative materials in intact teeth (caries and restoration free) with ideal access preparations (3-8). However, many teeth that require endodontic therapy have large restorations. Clinically, access preparations may be made in teeth with large restorations if the restoration is acceptable. The resulting temporary resto-
Joumal of Endodontics
Turner et al.
ration that seals the access cavity is placed in contact with both tooth structure and amalgam. In a recent isotope study that investigated the sealing properties oftemporary endodontic restorations placed in access preparations made through amalgam and composite resin restorations, all temporary, amalgam, and composite resin restorations leaked (18). The purpose of this study was to compare the sealing abilities of seven temporary restorative materials used to close access preparations made through amalgam restorations in extracted human teeth. A fluid filtration technique was used to measure leakage. MATERIALS AND METHODS Seventy extracted intact human molar teeth that were restoration and carics free were sectioned at the cementoenamel junction with a low-speed diamond saw (Isomer 111180; Buehler Ltd., Lake Bluff, 1L). A spoon excavator was used to remove the pulp tissue from the pulp chamber in the crown segments. Class I cavity preparations were made using a #245 carbide bur in a high-speed handpiece with copious water spray. After placement o f two layers of Copalite (Harry J. Bosworlh Co., Skokie, 1L), amalgam (Dispersalloy; Johnson & Johnson, East Windsor, N J) was condensed into the preparations and carved confluent with the cavosurface margins. The teeth with amalgam restorations were placed in Ringer's solution and 0.2% sodium azide for l wk. Stainless steel tubes (18 gauge) were fixed through the center o f Plexiglas squares (2 x 2 x 0.6 cm), to which the sectioned crowns were cemented with cyanoacrylate adhesive (Zapit; Dental Ventures of America, Inc., Anaheim Hills, CA) and oriented such that the pulp chambers were centered over the tube aperture. The Plexiglas squares with the mounted teeth were then attached by means of the 18-gauge tubes to a fluid filtration apparatus that would allow microleakage to be measured quantitatively (16, 17). Phosphate-buffered saline (Grand Island Biological Co., Grand Island, NY) containing 0.2% fluorescein dye (Sigma Chemical Co., St. Louis, MO) was introduced into the pulp chambers through the 18-gauge tubes at a constant pressure of 20 psi. As microleakage of the dye occurred around the temporary restoration, an air bubble within a 25-ul micropipette (Microcaps; Fisher Scientific, Philadelphia, PA) placed in the tubing system moved in the direction of fluid flow from the pulp chamber toward the occlusal surface. The movement of the bubble was directly proportional to the amount of fluid leakage and was measured in millimeters over a period o f I rain. With each tooth serving as its own control, a base line measurement for microleakage was obtained for each tooth 1 wk after insertion of the occlusal amalgam but before access preparation. Teeth with visible leakage at the tooth/restoration interface were rejected from this study. After the control measurements were obtained, access preparations were made in the amalgam restoration of each tooth using a #4 carbide bur in a high-speed handpiece with copious water spray. The access preparation was totally within the occlusal amalgam. Although it was not typical of an access preparation for a molar tooth, it was similar to that of a bicuspid tooth and adequate for proper restoration (Fig. 1). A cotton pellet was placed in the pulp chamber that allowed a 4-ram thickness o f temporary material. The access was then sealed with one of
FiG 1. Occlusal view of crown segment with class endodontic access preparation restored with Cavit.
seven temporary restorative materials: Cavit (Premier Dental Products, Norristown, PA), Cavit-G (Premier Dental Products), IRM (L. D. Caulk Division, Densply International Inc., Milford, DE), T E R M (L. D. Caulk Division), zinc phosphate cement (Tenacin; L. 1). Caulk Division), polycarboxylate cement (Durelon; Premier Dental Products), and a glass ionomer restorative material (Fuji II; G. C. International, Scottsdale, AZ). Ten teeth were restored with each material. The materials were all mixed and placed according to the manufacturer's instruction except for IRM, which was mixed with a powder to liquid (P:L) ratio of 2 g/ml. Powell et al. (19) recently demonstrated that IRM seals best when mixed with that P:L ratio. After placement of the test materials into the access preparations, the crowns were immediately inverted over vials containing Ringer's solution and 0.2% sodium azide (to inhibit microbial growth) so that the restoration was immersed in the liquid. Then the vials were placed in a covered dish and incubated in an oven at 37"C until time for measurements. Measurements for microleakage were made at 15 min, I h, 24 h, 1 wk, and 2 wk after the insertion of the temporary restoration. Between measurements, the teeth were stored in the Ringer's solution at 37"C. Measurements were made four times for each experimental tooth at each time period. These results were averaged and converted to ul/min 9 20 psi. Then the leakage values were converted to log base 10 to allow for inclusion of all data, including any possible outliers. Statistical analysis was performed using Statgraphics (Ver 2.1; STSC, Inc., Rockville, MD). Multiple range analysis of variance for each test material was performed at 95% confidence levels using Tukey's HSD intervals for means. RESULTS The mean microleakage values are listed in Table 1. Cavit, Cavit-G, IRM, T E R M and glass ionomer cement all provided an excellent seal against microleakage. There was no significant difference between the microleakage of these materials and the control teeth with class I amalgam restorations. No
Temporary Restorations in Amalgam
Vol. 16, No. 1, January 1990
TABLE 1. Mean microleakage measurements (#l/min.20 psi) Glass Ionomer
Control 15 min 1h
0.04 0.08 0.07
0.04 0.15 0.18
0.04 0.19 0.17
0.04 0.12 0.12
0.04 0.20 0.20
0.04 0.18 4.06"
0.04 0.14 0.60*
24 h 1 wk 2 wk
0.08 0.08 0.12
0.11 0.08 0.12
0.16 0.17 0.17
0.15 0.24 0.22
0.18 0.24 0.22
1.94* 2.19" 2.58"
5.73* 90.04" 90.04"
S~gnlflcantlyd~fferent,p < 0 05 (Tukey's HSOintewalsfor means)
visible microleakage occurred at the amalgam-temporary restoration interface in any of these teeth tested. Although zinc phosphate cemenl and polycarboxylate cement both provided excellent seals at the 15-rain measurement period, both showed visible microleakage at the amalgam-temporary restoration interface at the 1-h measurement. This leakage was statistically significant when compared with the control measurements. At l wk, the polycarboxylate cement group exhibited extensive microleakage (90.04 ~l/min 9 20 psi). DISCUSSION The results indicate that Cavil, Cavit-G, TERM, IRM, and glass ionomer cement placed in endodontic access preparations made entirely within amalgam provided a seal that was as leakproof as the control teeth which had class I preparations restored with amalgam alone. Zinc phosphate and polycarboxylate cements exhibited significantly greater leakage when compared with their controls. Measured microleakage values correlate well with those reported by Anderson et al. (17) using similar methodology. The results of this study support other studies (3, 4, 10, 17) demonstrating that Cavil and Cavit-G provided effective seals but contradict the findings of other studies (5, 6, 8, 9, 11). This discrepancy may be explained by the 4-ram thickness of Cavit and Cavit-G used in the present study. Webber et al. (12) recommended that at least 3.5 mm of Cavil be used to ensure a leakproof seal. Cavit and Cavit-G are hygroscopic materials and expand when they come into contact with water. This expansion permits the material to adapt very tightly 1o the prepared cavity, thus providing an excellent seal (20). TERM, a premixed material that is injected into the access preparation and light cured for 20 s to provide a hard surface, was also found to provide an effective seal against microleakage. This is in agreement with Anderson et al. (17). Allhough IRM was not used at the manufacturer's recommended P:L ratio, observations in the present investigation sustain previous studies (4, 6, 9) which demonstrated that ZOE-based materials provide adequate seals against microleakage. At the P:L ratio of 2 g/ml used in this study, the material was thin, thus making its placement into the access preparations difficult. Allhough a good seal was created, it is not known how strength or durability would be affected in the oral environment. Zinc phosphate cement did not demonstrate leakage after 15 min, but after 1 h significant visible and measurable leakage was present in 5 of 10 (50%) experimental teeth and increased at each successive measurement period. Previous studies reported that zinc phosphate cement provides a poor seal (3, 4, 10) whereas Krakow et al. (6) reported some zinc
phosphate products provided excellent seals. The 1-h measurement showed the highest mean leakage of the zinc phosphate cement group undoubtably because one crown exhibited an inordinately high measurement of 27.61 ul/min 9 20 psi. By 1 wk, this had fallen to 5.58 ul/min 9 20 psi but it increased again after 2 wk. This material required mixing a powder and liquid. The manufacturer's instructions were followed for mixing the material for cementation purposes. Because of its thin consistency, the cement was difficult to place in the access preparations. Usually a thicker mixture is used as a temporary restoration; however, Pashley et al. (21) found cement mixtures of a thinner consistency provided the best seals. Further studies are necessary 1o determine the optimal P:L ratio for zinc phosphate cement. In agreement with the findings of Marosky et al. (10), polycarboxylate cement showed extensive visible and measurable leakage after 1 h in most teeth tested. By 1 wk all but one toolh showed extensive leakage. This material also required mixing a powder and liquid and it was difficult to place in the access preparations. The premixed temporary materials all provided excellent seals, which is consistent with findings of Marosky et al. (10), Chohayeb and Bassiouny (3), and Anderson et al. (17). In contrast, two out of the four materials requiring mixing (zinc phosphate cement and polycarboxylate cement) showed significant leakage after 1 h. Manipulation of these materials may lead to increased leakage. Thermocycling was not done in this study. A pilot project found that thermocycling resulted in microleakage between the amalgam and the tooth and made determining the amount of leakage at the amalgam-temporary restoration interface impossible. This confirms the findings of Derkson et al. (16) who, using the same technique, found that thermocycling increased the amount of microleakage at the amalgam-tooth interface. Orahood et al. (18) also reported leakage of the amalgam and composite resin restorations after thermocycling. The clinical significance of thermocycling has been questioned since teeth in situ are in contact with heat or cold for only a short time (22). The fluid filtration technique proved to be an excellent method for quantitatively measuring microleakage around temporary endodontic restorative materials. Although the fluid is forced under pressure in a pulpal-coronal direction in this technique, as opposed 1o a coronal-pulpal direction, it easily detects a lack of marginal seal. Derkson et al. (16) and Anderson et al. (17) tested fluid flow in both directions and found no difference in the amount of microleakage. This research was supported in part by a Grant-=n-A~lof Researchfrom the Endowment and Memorial Foundation of the American Association of Endodontlsts.
Turner et al.
Journal of Endodontics
The opinions, assertions, materials, and methodologies herein are private ones of the authors and are riot to be construed as official or reflecting the views of the American Asso~ation of Endodontists or the Endowment and Memorial Foundation. Dr. Turner is a former eododontic postgraduate student, Medical College of Georg=a, School of Dentistry. Augusta, GA and is currently in private endodontic practice, Atlanta. Dr. Anderson is associate professor and director of Postgraduate Endodontics, Medical College of Georgia, School of Dentistry. Dr. Pashley is professor, Department of Oral Biology, Medical College of Georgia, School of Dentistry. Dr. Pantera is assistant professor, Department of Endodontics, Medical ColleOe of Georgia, Sctloo4 of Dentistry.
References 1. Kakahashi S, Stanley HR, Fitzgerald RJ. The effects of surgical exposures of dental pulps in germ-free and conventional laboratory rats. Oral Surg 1965;20:340-9. 2. Swanson K, Madison S. An evaluation of coronal microleakage in endodontJcally treated teeth. Part I. Time periods. J Endodon 1987;13:56-9. 3. Chotlayeb AA, Bassiouny MA Sealing ability of intermediate restoratives used in endodontics. J Endodon 1985;11:241-4. 4. Parns L, Kapsimalis P, Cobe HH, Evans R The effect of temperature change on the sealing properties of temporary filling materials Part II. Oral Surg 1964;17:771-8. 5. Tamse A, Ben-Amar A, Gover A. Sealing properties of temporary filling materials used in endodontics. J Endodon 1982;8:322-5. 6. Krakow AA, deStoppelaar JD, Gron P. In vivo study of temporary filling matenals used in endodontK,-s in anterior teeth Oral Surg 1977;43:615-20. 7. Blaney TD, Peters DD, Setterstrom J, Bemier WE Marginal sealing quality of IRM and Cavil as assessed by microbial penetration. J Endodon 1981 ;7:453-7.
8. Keller DL, Peters DD, Setterstrom J, Bernier WE. Microleakage of softened temporary restorations as determined by microorganism penetration. J Endodon 1981 ;7:413-7. 9. Friedman S, Shani J, Stabbe~z A, Kaplawl J. Comparative sealing ability of temporary filling materials evaluated by leakage of radiosodium. Int Endod J 1986;19:187-93. 10. Marosky JE, Patterson SS, Swartz M Marginal leakage of temporary sealing materials used between endedontic appointments and assessed by calcium 45--an in vitro study. J Endodon 1977;3:110-3. 11. Todd MJ, Hamson JW. An evaluation of the immediate and early sealing properties of Cavit. J Endodon 1979;5:362-7. 12. Webber RT, del Rio CE, Brady JM, Segall RO. Sealing quality of a temporary filling material. Oral Surg 1978;46:123-30. 13. Matloff IR, Jensen JR, Singer L, Tabibi A. A comparison of methods used in root canal sealabiltty studies. Oral Surg 1982;53:203-8 14. Gocng RE. Microleakage around dental restorations: a summanzing review. J Am Dent Assoc 1972;84:1349-57. 15. Delivanis PD, Chapman KA. Comparison and reliability of technElues for measuring leakage and marginal penetration. Oral Surg 1982:53:410-6. 16. Derkson GD, Pashley DH. Derkson ME. Microleakage measurement of selected restorative materials: a new in vitro method. J Prosthet Dent 1986;56:435-40. 17. Anderson RW, Powell BJ, Pashley DH. Microleakage of three temporary endodontJc restorations. J Endodon 1988; 14:497-501. 18. Orahood JP, Cochran MA, Swartz M. Newton CW. In vitro study of marginal leakage between temporary sealing materials and recently placed restorative materials. J Endodon 1986;12:523-7. 19. Powell B, Anderson R, Pashley D. Microleakage of IRM used to restore endedontic access preparations [Abstract 1522}. J Dent Res 1988;67:303. 20. W~errnan FH, Eames WB, Serene TP. The physical and biologic properties of Cavil. J Am Dent Assoc 1971;82:378-82. 21. Pashley EL, Tao L, Pashley DH The sealing properties of temporary filling materials. J Prosthet Dent 1988;60:292-7. 22. Trowbddge HO Model systems for determining biologic effects of mlcroleakage Oper Dent 1987;12:164-72.