Addition of Fresh Amalgam to Existing Amalgam: Microleakage Study C. Leelawat, D.D.S., M.S.," W . Scherer, D.D.S., ' J . Clzang, D.D.S.,+ A. Schulman, D.D.S., M.S.,j and T. Vijayaraghavan, Ph.D. '
The purpose of this in uitro study was to determine whether adhesive lining materials reduce microleakage in amalgam restorations, and to observe the degree of microleakage at the interface between freshly placed (new) and existing (old) amalgam. Forty-eight specimens were used in the experimental groups. The materials used to study microleakage in this investigation were: copal varnish, a dentin bonding agent (ClearfilNew Bond),and a 4-META adhesive (Amalgambond). No significant difference in microleakage was found at the interfaces between freshly placed and existing amalgam. Significantlyless microleakage was noted in specimens using the 4-META adhesive and the dentin bonding agent as compared to specimens in which no lining material was placed. Significantlyless microleakage was noted in specimens using the 4-META adhesive compared to specimens using cavity varnish.
METHODS AND MATERIALS
D
ental amalgam satisfies many of the criteria of an ideal restorative despite the development of many new restorative materials. However, the question of how, or whether, to repair a defective amalgam still remains questionable. In this regard, several investigators have noted the incidence of microleakage at the interfaces of such repaired restoratives.',2 Thus, in order to diminish the incidence caused by such microleakage, adhesive dental materials have recently been considered to function as liners for such amalgam restoration^.^ These adhesive liners may establish a bond to tooth structure and amalgam, aid in sealing a margin, and limit mi~roleakage.~.~ The dual purpose of this study was to investigate whether adhesive lining materials reduce microleakage in amalgam restorations, and to observe the degree of microleakage at the interface between freshly placed and existing amalgam.
Forty-eight freshly extracted, noncarious, permanent molar teeth, which had been stored in a 10percent buffered formalin solution for no longer than 1 month, were used in this study. Class I preparations were prepared to a depth of 2.5 mm using a No. 556 diamond bur in a high-speed handpiece with water coolant. The preparations were then washed thoroughly with water and air dried. Two coats of Cavity Varnish (copal) (Sultan Chemists Inc., Englewood, NJ) were applied to the walls and floors of the preparations and allowed to air dry. Dispersalloy amalgam (Johnson and Johnson, East Windsor, NJ) was inserted into all the prepared teeth, condensed, carved, and flnished according to manufacturer's specitlcations. The restorations were polished 24 hours later using a n amalgam polishing kit (Shofu Polishing Kit, Shofu Dental Manufacturing Co. Menlo Park, CA). All specimens were stored in physiologic saline at 37°C for 7 days before proceeding with the study. The specimens were randomly separated into four groups of 12 teeth each according to the lining materials used as follows:
* Graduate Student, Department of Dental Materials Science, New York University College of Dentistry: t Assistant Professor and Director. Advanced Education Program in General Dentistry. New York University College of Dentistry: 'Professor and Chairman.Department of Dental Materials Science. New York Universlty College of Dentistry: 'Assistant Professor. Department of Dental Materials Science. New York University College of Dentistry, New York. New York $Assistant Professor. Department of Prosthetics. University of Texas, Houston, Texas Address reprint requests to W. Scherer. D.D.S.. Director. Advanced Education Program in General Dentistry, New York University College of Dentistry. 345 East 24th Street, New York. NY 10010 01992 Decker Periodicals Inc.
Group I - No lining material - control. Group 11- Cavity varnish. Group 111 - 4-META (4-Methacryloxyethyltrimellitate anhydride) adhesive (Amalgam-bond,Parkell Products, Farmingdale, NYI. Group IV - Dentin bonding agent (ClearAl New 41
JOURNAL OF ESTHETIC DENTISTRY VOLUME 4. NUMBER 2 March/April 1992
and finished. Twenty-four hours later the restorations were polished with an amalgam polishing kit. All tooth surfaces were covered with two layers of clear nail polish and one layer of polyurethane varnish, except for an area 2.0 mm around the restorations. All specimens were then thermocycled by groups in 0.5 percent basic fuchsin dye between 5°C and 55°C with a dwell time of 1 minute a t each temperature. Each specimen was thermocycled 200 times. Following the thermocycling procedures, every specimen was mounted in a n acrylic block and sectioned facio-lingually with a high concentration Diamond Wafering Blade (Buehler Ltd., W e Bluff, IL). The longitudinal sections were examined for microleakage under a light microscope at 20 x magnification. The depth of dye penetration was evaluated by using a standardized system as suggested by GoingZ (Fig. 2) according to the following scale:
Bond. Kuraray Co., Ltd., Osaka, Japan and J. Morita. Tustin, CA). For all specimens, one half of the previously placed amalgam restorations were removed with a No. 556 diamond bur in a high-speed handpiece with water coolant (Fig. 1). The depth of these new preparations also measured 2.5 mm. All preparations were thoroughly washed with water and air dried. Each group was then treated before the insertion of amalgam a s follows: Group I - N o lining material was placed. This was the control group. Group II - Two separate applications of cavity varnish were applied to the previously placed amalgam surface as well as the walls of the preparation and allowed to air dry. Group III - Amalgambond Activator was applied to both enamel and the previously placed amalgam surface as well as all of the enamel walls of the preparation for 30 seconds and to the dentinal surfaces for 10 seconds. The surfaces were then rinsed and air dried. Two drops of Amalgambond base were mixed with one drop of catalyst to form the adhesive liner. The liner was placed on all walls of the preparations as well a s the previously placed amalgam surface. Group IV - All enamel margins were etched with a 37 percent phosphoric gel etchant for 15 seconds. One drop of New Bond Catalyst and one drop of New Bond Universal were mixed together and applied on all the preparation walls and the previously placed amalgam surface.
Degree 0 - No penetration of dye. Degree 1 - Penetration of u p to a half of the wall depth. Degree 2 - Penetration of dye to the floor of the cavity. but not including it. Degree 3 - Penetration of dye completely surrounding the fdling, including the cavity floor. Degree 4 - Diffusion of dye into the dentin under the floor or base of the cavity. Degree 5 - Penetration of dye through the dentin to the pulp chamber.
RESULTS The distribution of leakage scores at the interfaces between previously placed amalgam and fresh amalgam is listed in Table 1. A n ANOVA showed that there was no significant difference in microleakage between the four experimental groups at the interface area.
After each of the lining materials were placed, Dispersalloy amalgam was inserted, condensed, carved,
I Figure 1.
\ Areas representing &sting (old) and fresh (new)
Figure 2. Degree or depth of dye penetration.
amalgam.
42
Addition of Fresh to Existing Amalgam
The distribution and median leakage scores at the freshly placed amalgam side are shown in Table 2. Group I (no liner) exhibited the highest median leakage score, followed by Group I1 (cavity varnish). Group N (Clearfil New Bond), and Group I11 (4-META adhesive) (Figs.3 to 6).Comparisons (Table3)were made between Group I and Groups 11,111, and IV.Groups I11 (4-META adhesive) and IV (Clearfil New Bond) exhibited significantly less leakage when compared to Group I (no liner). (p < .0005, p < .0025 ANOVA) respectively. No significant differences were noted between Group I (no liner) and I1 (cavity varnish) (p < .25 ANOVA). Similar statistical analyses were undertaken in comparing Groups I11 (4-METAadhesive)and IV (Clearfil New Bond) to Group I1 (cavityvarnish) (Table4). Significantly less leakage was noted when the 4-META adhesive, Group 111, was compared to Group 11, cavity varnish, (p < .025 ANOVA), whereas no significant difference was noted between Clearfil New Bond (Group rvl and the cavity varnish, (Group 11) (p < .1 ANOVA). The distribution of leakage scores with cavity varnish at the previously placed amalgam side is shown in Table 5. I t should be noted that the median leakage
score of 2 is similar to the median leakage score at the fresh amalgam side.
DISC USSl 0N Adhesive resin materials have been reported to seal cavity margins and thereby help reduce microleakage around re~torations.~-~ This study utilized two such materials: a 4-META adhesive and a phosphate ester dentin bonding agent. The 4-META adhesive contains both hydrophobic and hydrophilic groups that promote adhesion to tooth structure upon polymerization. It has been demonstrated that this adhesive bonds to enamel, dentin, and various metal The phosphate ester dentin bonding agent used in this study is similar to an adhesive resin material (Panavia, Kuraray and J. Morita) that has gained popularity in acting as a luting agent for resin-bonded fxed partial dentures. The results of this study indicate that less microleakage was observed in restorations utilizing the 4META adhesive and the phosphate ester dentin bonding agent compared to restorations where no liners had been placed. I t should be noted that the presence of a smear layer can contribute to microleakage.I6.l7Both the 4-META and phosphate ester dentin bonding agent system sufficiently remove or alter the smear layer. As a result, these materials may interact with the altered smear layer or bond to the dentin substrate. Thus, the amalgam can adapt better to cavity walls and reduce the interfacial space through which fluid may flow. Furthermore, the 4-META adhesive may have the ability to form organometallic bonds with the amalgam alloy and contribute to reducing microleakage. The 4-META adhesive produced significant reductions in microleakage when compared to those specimens in which no liner was placed or in those specimens using cavity varnish.
Table 1. Distributionof Leakage Scores at the interface between Existing Amalgam and Fresh Amalgam Experimental GrouDs
Total No. of Teeth
Site of Leakage
0 1 2 3 4 5
7 10 11 IV -Clearfil NewBond 11 I -Without liner I1 -CavityVarnish I11 -4-METAAdhesive
0 0 0 0 0 0 0 0
2 0 1 0
0 0 0 0
3 2 0 1
12 12 12 12
Table2. DistributionofLedtageScoresatFreshAmalgcmSite Experimental Groups I -Without liner
Median Total No. Leakage of Teeth Scores
Site of Leakage
0 J 2 3 4 5 1 1 1 2 3 4
12
4
3 2 2 1 1 3
12
2
7 3 1 1 0 0
12
0
5 4 2 0 0 1
12
1
Table 4. Comparisons between the Cavity Varnish and Other liners
II -Cavity Varnish 111 -4-META Adhesive IV -Clearfil NewBond
Experimental Groups 111 -4-META Adhesive W -Clearfil New Bond
Table 3. Comparisons between the Control (No liner) and Experimental Groups Experimental Groups
II - Cavity Varnish I11 -4-META Adhesive IV -Clearfil New Bond
p-Value
p-Value
Significant Difference in Microleakage
0.01 < p < 0.025
Yes
0.05 < p < 0.1
No
Table 5. Distribution of leakage Scores at Existing Amalgam Side (Side Control)
Significant Difference in Microleakage
0.1 < p < 0.25
No
Experimental Group
p < 0.005
Yes
I1 -Cavity
0.001 > p c 0.0025
Yes
Varnish
43
Site of Leakage 0 I 2 3 4 5
119 8 7 211
Median Total No. Leakage ofleeth Scores
48
2
JOURNAL.OF ESTHETIC DENTISTRY VOLUME 4. NUMBER 2
March/Aprll 1992
Even though microleakage was observed with cavity varnish. it has the ability to act as a barrier in limiting microleakage. and its beneficial effects in this regard have been demonstrated in numerous studies.IGz1It is entirely possible, however, that the effects of thermocycling may have reduced its ability to prevent microleakage in this study.22It should also be noted that some investigators have expressed concern over the possibility of dissolution of cavity varnish in the oral cavity. An in vitro study also demonstrated the occurrence of a 4 to 24 percent loss of cavity varnish weight per weekz3 No significant differences were observed at the interfaces between the existing and freshly placed amalgams. The bond between the two amalgams is probably due to the fact that free mercury from the fresh amalgam combined with the set amalgam and caused a union between the two groups by the formation of new intermetallic 25 At the same time, if any microgaps were to occur, one would expect larger microgaps to form between the amalgam and cavity wall, rather than between the fresh and existing amalgam. This occurs because the linear coefficient of thermal expansion of amalgam is about two to three times that of surrounding tooth structure. Thus, thermal changes may affect the sealing capacity of the amalgam at the cavity walls, but not between the fresh and existing amalgams. The results of this study appear to confim the results of other studies that indicate that initial leakage ratings for high-copper amalgams appear to be high due to the resistance of these amalgams to undergo corrosion.22.26. 27
Figure 3. Control - no lining material. Microleakage under amalgam restoration.
CONCLUSIONS 1 . No significant differences in microleakage were noted at the interfaces between fresh and existing
Figure 4. Cavity varnish; N = fresh amalgam: 0 = exlsting amalgam.
amalgam. 2. Significantly less microleakage was noted in specimens using the 4-META adhesive and the phosphate dentin bonding agent as compared to specimens in which no lining material was used. 3. SigniAcantlyless microleakage was n-otedin specimens using the 4-META adhesive as compared to specimens using cavity varnish.
REFERENCES 1. Consani S.Ruhnke MP. StolfwL. Inflltration of radioactive solution intojoined silver-amalgam.J Prosthet Dent 1977;
37:158-163. 2. Going RE, Massler M. Dute HL. Marginal penetration of dental restorations as studied by crystalvioletdye and 131. J Am Dent Assoc 1960; 61:285-300. 3. Varga J. Matsumura H, Masuhara E. Bonding of amaJgam fillingto tooth cavitywfth adhesive resin.Dent Mater 1986; 5:158-164. 4. Ben-AmarA.NordenbergD, Uberman R, FisherJ. Gorfil C. The control of marginal microleakage in amalgamrestora-
IFiepre 5. 4-META Adhesive; minimalto no microleakage.
44
Addition of Fresh to Existing Amalgam
12. Atsuta M. Abell AK. Turner DT. Nakabayashi N. Takeyama M. A new coupling agent for composite materials. 4-META.
Figure 6.ClearlX New Bond: minimal microleakage.
5.
6.
7.
8.
9. 10.
11.
tions using a dentin adhesive. A pilot study. Dent Mater 1987; 3:94-96. Shimizu A, Ui T, Kawakami M. Microleakage of amalgam restorations with adhesiveresin cement lining, glass ionomer cement base and fluoride treatment. Dent Mater 1987: 6:64-69. Yu X Y , Wei G, Xu J W .Experimental use of bonding agent to reduce marginal microleakage tests. Quintessence lnt 1987: 18:783-787. Staninec M, Holt M. Bondingof amalgam to tooth structure tensile adhesion and microleakage tests. J Prosthet Dent 1988; 59:397-402. Nakabayashi N. Kojima K, Masuhara E. Studies on dental self curing resins (24).Adhesion to dentin by mechanical Dent M a t Device 1982: 1:74. interlocking. J J a p SOC Swift E J Jr. New adhesive resins. A status report for the American Journal of Dentistry.Am J Dent 1989; 2:358-360. Takeyama M. Kashibuchi N, Nakabayashi N, Masuhara E. Studies on dental self-curing resin ( 17).Adhesion of PMMA with bovine enamel or dental alloys. J J p n Soc Dent Apparatus Mater 1978; 19:179. Nakabayashi N, Takeyama M. Kojima K. Masuhara E. Studies on dental self-curing resins (20).Adhesion mechaDent nism of4-META/MMA-TBB resin to dentin. J J p n SOC Apparatus Mater 1982: 23:34.
J Biomed Mater Res 1982: 16:619. 13. Atsuta M. Nagata K, Turner DT. Strong composites of dimethacwlates with 4-META. J Biomed Mater Res 1983: 17:679. 14. TanakaT. Nagata K. Takeyama M, Nakabayashi N. Masuhara E. Heat treatment of gold alloy to get adhesion with resin. J J p n SOC Apparatus Mater 1980; 21:95. 15. Tanaka T. Nagata K. Takeyama M, Atsuta M, Nakabayashi N. Masuhara E. 4-METAopaqueresin. Anew resin strongly adhesive to nickel chromium alloy. J Dent Res 1981: 60: 1697-1706. 16. Pashley DH, Depew DD. Effects of the smear layer. copalite and oxalate on microleakage. Oper Dent 1986: 11:95-102. 17. Jodaikin A, Austin JC. The effects of cavity smear layer removal on experimental marginal leakage around amalgam restorations. J Dent Res 1981: 60:1861-1866. 18. Barber D, Lyell J. Massler M. Effectiveness of copal resin varnish under amalgam restorations. J F'rosthet Dent 1964: 14:533-536. 19. Lyell J. Barber D, Massler M. Effects of saliva and sulphide solution on the marginal seal of amalgam restorations. J Dent Res 1964; 43:375-379. 20. Swartz ML. Phillips RW. In vitro studies on the marginal leakage of restorative materials. J Am Dent Assoc 1961: 62: 141- 151. 21. Fanian F. Hadavi F, Asgar K. Marginal leakage of dental amalgams. Effects of cavity varnish and burnishing. Can Dent Assoc J 1984; 50:484487. 22. Smith GA, Wilson NHF, Combe EC. Microleakageofconventional and ternary amalgam restorations in vitro. Br Dent J 1978: 144~69-73. 23. Powel GL, Daines DT. Solubility of cavity varnish: a study in vitro. Oper Dent 1987; 12:48-52. 24. Kirk EEJ. Amalgam to amalgam bond, a p r e l i m i n q report. Dent Pract 1962; 12:371. 25. Terkla LG. Mahler DB, Mitchem JG. Bond strength of repaired amalgam. J Prosthet Dent 1961; 11:942-947. 26. Wilson NHF. Smith GA. The in vitro behavior of a cavity liner under amalgam restorations. Br Dent J 1978 145331-334. 27. Andrews JT, Hembree J H . Marginal leakage of amalgam alloys with high content ofcopper: a laboratory study. Oper Dent 1980; 5:7-10.
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The purpose of this in uitro study was to determine whether adhesive lining materials reduce microleakage in amalgam restorations, and to observe the degree of microleakage at the interface between freshly placed (new) and existing (old) amalgam. Forty-eight specimens were used in the experimental groups. The materials used to study microleakage in this investigation were: copal varnish, a dentin bonding agent (ClearfilNew Bond),and a 4-META adhesive (Amalgambond). No significant difference in microleakage was found at the interfaces between freshly placed and existing amalgam. Significantlyless microleakage was noted in specimens using the 4-META adhesive and the dentin bonding agent as compared to specimens in which no lining material was placed. Significantlyless microleakage was noted in specimens using the 4-META adhesive compared to specimens using cavity varnish.
METHODS AND MATERIALS
D
ental amalgam satisfies many of the criteria of an ideal restorative despite the development of many new restorative materials. However, the question of how, or whether, to repair a defective amalgam still remains questionable. In this regard, several investigators have noted the incidence of microleakage at the interfaces of such repaired restoratives.',2 Thus, in order to diminish the incidence caused by such microleakage, adhesive dental materials have recently been considered to function as liners for such amalgam restoration^.^ These adhesive liners may establish a bond to tooth structure and amalgam, aid in sealing a margin, and limit mi~roleakage.~.~ The dual purpose of this study was to investigate whether adhesive lining materials reduce microleakage in amalgam restorations, and to observe the degree of microleakage at the interface between freshly placed and existing amalgam.
Forty-eight freshly extracted, noncarious, permanent molar teeth, which had been stored in a 10percent buffered formalin solution for no longer than 1 month, were used in this study. Class I preparations were prepared to a depth of 2.5 mm using a No. 556 diamond bur in a high-speed handpiece with water coolant. The preparations were then washed thoroughly with water and air dried. Two coats of Cavity Varnish (copal) (Sultan Chemists Inc., Englewood, NJ) were applied to the walls and floors of the preparations and allowed to air dry. Dispersalloy amalgam (Johnson and Johnson, East Windsor, NJ) was inserted into all the prepared teeth, condensed, carved, and flnished according to manufacturer's specitlcations. The restorations were polished 24 hours later using a n amalgam polishing kit (Shofu Polishing Kit, Shofu Dental Manufacturing Co. Menlo Park, CA). All specimens were stored in physiologic saline at 37°C for 7 days before proceeding with the study. The specimens were randomly separated into four groups of 12 teeth each according to the lining materials used as follows:
* Graduate Student, Department of Dental Materials Science, New York University College of Dentistry: t Assistant Professor and Director. Advanced Education Program in General Dentistry. New York University College of Dentistry: 'Professor and Chairman.Department of Dental Materials Science. New York Universlty College of Dentistry: 'Assistant Professor. Department of Dental Materials Science. New York University College of Dentistry, New York. New York $Assistant Professor. Department of Prosthetics. University of Texas, Houston, Texas Address reprint requests to W. Scherer. D.D.S.. Director. Advanced Education Program in General Dentistry, New York University College of Dentistry. 345 East 24th Street, New York. NY 10010 01992 Decker Periodicals Inc.
Group I - No lining material - control. Group 11- Cavity varnish. Group 111 - 4-META (4-Methacryloxyethyltrimellitate anhydride) adhesive (Amalgam-bond,Parkell Products, Farmingdale, NYI. Group IV - Dentin bonding agent (ClearAl New 41
JOURNAL OF ESTHETIC DENTISTRY VOLUME 4. NUMBER 2 March/April 1992
and finished. Twenty-four hours later the restorations were polished with an amalgam polishing kit. All tooth surfaces were covered with two layers of clear nail polish and one layer of polyurethane varnish, except for an area 2.0 mm around the restorations. All specimens were then thermocycled by groups in 0.5 percent basic fuchsin dye between 5°C and 55°C with a dwell time of 1 minute a t each temperature. Each specimen was thermocycled 200 times. Following the thermocycling procedures, every specimen was mounted in a n acrylic block and sectioned facio-lingually with a high concentration Diamond Wafering Blade (Buehler Ltd., W e Bluff, IL). The longitudinal sections were examined for microleakage under a light microscope at 20 x magnification. The depth of dye penetration was evaluated by using a standardized system as suggested by GoingZ (Fig. 2) according to the following scale:
Bond. Kuraray Co., Ltd., Osaka, Japan and J. Morita. Tustin, CA). For all specimens, one half of the previously placed amalgam restorations were removed with a No. 556 diamond bur in a high-speed handpiece with water coolant (Fig. 1). The depth of these new preparations also measured 2.5 mm. All preparations were thoroughly washed with water and air dried. Each group was then treated before the insertion of amalgam a s follows: Group I - N o lining material was placed. This was the control group. Group II - Two separate applications of cavity varnish were applied to the previously placed amalgam surface as well as the walls of the preparation and allowed to air dry. Group III - Amalgambond Activator was applied to both enamel and the previously placed amalgam surface as well as all of the enamel walls of the preparation for 30 seconds and to the dentinal surfaces for 10 seconds. The surfaces were then rinsed and air dried. Two drops of Amalgambond base were mixed with one drop of catalyst to form the adhesive liner. The liner was placed on all walls of the preparations as well a s the previously placed amalgam surface. Group IV - All enamel margins were etched with a 37 percent phosphoric gel etchant for 15 seconds. One drop of New Bond Catalyst and one drop of New Bond Universal were mixed together and applied on all the preparation walls and the previously placed amalgam surface.
Degree 0 - No penetration of dye. Degree 1 - Penetration of u p to a half of the wall depth. Degree 2 - Penetration of dye to the floor of the cavity. but not including it. Degree 3 - Penetration of dye completely surrounding the fdling, including the cavity floor. Degree 4 - Diffusion of dye into the dentin under the floor or base of the cavity. Degree 5 - Penetration of dye through the dentin to the pulp chamber.
RESULTS The distribution of leakage scores at the interfaces between previously placed amalgam and fresh amalgam is listed in Table 1. A n ANOVA showed that there was no significant difference in microleakage between the four experimental groups at the interface area.
After each of the lining materials were placed, Dispersalloy amalgam was inserted, condensed, carved,
I Figure 1.
\ Areas representing &sting (old) and fresh (new)
Figure 2. Degree or depth of dye penetration.
amalgam.
42
Addition of Fresh to Existing Amalgam
The distribution and median leakage scores at the freshly placed amalgam side are shown in Table 2. Group I (no liner) exhibited the highest median leakage score, followed by Group I1 (cavity varnish). Group N (Clearfil New Bond), and Group I11 (4-META adhesive) (Figs.3 to 6).Comparisons (Table3)were made between Group I and Groups 11,111, and IV.Groups I11 (4-META adhesive) and IV (Clearfil New Bond) exhibited significantly less leakage when compared to Group I (no liner). (p < .0005, p < .0025 ANOVA) respectively. No significant differences were noted between Group I (no liner) and I1 (cavity varnish) (p < .25 ANOVA). Similar statistical analyses were undertaken in comparing Groups I11 (4-METAadhesive)and IV (Clearfil New Bond) to Group I1 (cavityvarnish) (Table4). Significantly less leakage was noted when the 4-META adhesive, Group 111, was compared to Group 11, cavity varnish, (p < .025 ANOVA), whereas no significant difference was noted between Clearfil New Bond (Group rvl and the cavity varnish, (Group 11) (p < .1 ANOVA). The distribution of leakage scores with cavity varnish at the previously placed amalgam side is shown in Table 5. I t should be noted that the median leakage
score of 2 is similar to the median leakage score at the fresh amalgam side.
DISC USSl 0N Adhesive resin materials have been reported to seal cavity margins and thereby help reduce microleakage around re~torations.~-~ This study utilized two such materials: a 4-META adhesive and a phosphate ester dentin bonding agent. The 4-META adhesive contains both hydrophobic and hydrophilic groups that promote adhesion to tooth structure upon polymerization. It has been demonstrated that this adhesive bonds to enamel, dentin, and various metal The phosphate ester dentin bonding agent used in this study is similar to an adhesive resin material (Panavia, Kuraray and J. Morita) that has gained popularity in acting as a luting agent for resin-bonded fxed partial dentures. The results of this study indicate that less microleakage was observed in restorations utilizing the 4META adhesive and the phosphate ester dentin bonding agent compared to restorations where no liners had been placed. I t should be noted that the presence of a smear layer can contribute to microleakage.I6.l7Both the 4-META and phosphate ester dentin bonding agent system sufficiently remove or alter the smear layer. As a result, these materials may interact with the altered smear layer or bond to the dentin substrate. Thus, the amalgam can adapt better to cavity walls and reduce the interfacial space through which fluid may flow. Furthermore, the 4-META adhesive may have the ability to form organometallic bonds with the amalgam alloy and contribute to reducing microleakage. The 4-META adhesive produced significant reductions in microleakage when compared to those specimens in which no liner was placed or in those specimens using cavity varnish.
Table 1. Distributionof Leakage Scores at the interface between Existing Amalgam and Fresh Amalgam Experimental GrouDs
Total No. of Teeth
Site of Leakage
0 1 2 3 4 5
7 10 11 IV -Clearfil NewBond 11 I -Without liner I1 -CavityVarnish I11 -4-METAAdhesive
0 0 0 0 0 0 0 0
2 0 1 0
0 0 0 0
3 2 0 1
12 12 12 12
Table2. DistributionofLedtageScoresatFreshAmalgcmSite Experimental Groups I -Without liner
Median Total No. Leakage of Teeth Scores
Site of Leakage
0 J 2 3 4 5 1 1 1 2 3 4
12
4
3 2 2 1 1 3
12
2
7 3 1 1 0 0
12
0
5 4 2 0 0 1
12
1
Table 4. Comparisons between the Cavity Varnish and Other liners
II -Cavity Varnish 111 -4-META Adhesive IV -Clearfil NewBond
Experimental Groups 111 -4-META Adhesive W -Clearfil New Bond
Table 3. Comparisons between the Control (No liner) and Experimental Groups Experimental Groups
II - Cavity Varnish I11 -4-META Adhesive IV -Clearfil New Bond
p-Value
p-Value
Significant Difference in Microleakage
0.01 < p < 0.025
Yes
0.05 < p < 0.1
No
Table 5. Distribution of leakage Scores at Existing Amalgam Side (Side Control)
Significant Difference in Microleakage
0.1 < p < 0.25
No
Experimental Group
p < 0.005
Yes
I1 -Cavity
0.001 > p c 0.0025
Yes
Varnish
43
Site of Leakage 0 I 2 3 4 5
119 8 7 211
Median Total No. Leakage ofleeth Scores
48
2
JOURNAL.OF ESTHETIC DENTISTRY VOLUME 4. NUMBER 2
March/Aprll 1992
Even though microleakage was observed with cavity varnish. it has the ability to act as a barrier in limiting microleakage. and its beneficial effects in this regard have been demonstrated in numerous studies.IGz1It is entirely possible, however, that the effects of thermocycling may have reduced its ability to prevent microleakage in this study.22It should also be noted that some investigators have expressed concern over the possibility of dissolution of cavity varnish in the oral cavity. An in vitro study also demonstrated the occurrence of a 4 to 24 percent loss of cavity varnish weight per weekz3 No significant differences were observed at the interfaces between the existing and freshly placed amalgams. The bond between the two amalgams is probably due to the fact that free mercury from the fresh amalgam combined with the set amalgam and caused a union between the two groups by the formation of new intermetallic 25 At the same time, if any microgaps were to occur, one would expect larger microgaps to form between the amalgam and cavity wall, rather than between the fresh and existing amalgam. This occurs because the linear coefficient of thermal expansion of amalgam is about two to three times that of surrounding tooth structure. Thus, thermal changes may affect the sealing capacity of the amalgam at the cavity walls, but not between the fresh and existing amalgams. The results of this study appear to confim the results of other studies that indicate that initial leakage ratings for high-copper amalgams appear to be high due to the resistance of these amalgams to undergo corrosion.22.26. 27
Figure 3. Control - no lining material. Microleakage under amalgam restoration.
CONCLUSIONS 1 . No significant differences in microleakage were noted at the interfaces between fresh and existing
Figure 4. Cavity varnish; N = fresh amalgam: 0 = exlsting amalgam.
amalgam. 2. Significantly less microleakage was noted in specimens using the 4-META adhesive and the phosphate dentin bonding agent as compared to specimens in which no lining material was used. 3. SigniAcantlyless microleakage was n-otedin specimens using the 4-META adhesive as compared to specimens using cavity varnish.
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37:158-163. 2. Going RE, Massler M. Dute HL. Marginal penetration of dental restorations as studied by crystalvioletdye and 131. J Am Dent Assoc 1960; 61:285-300. 3. Varga J. Matsumura H, Masuhara E. Bonding of amaJgam fillingto tooth cavitywfth adhesive resin.Dent Mater 1986; 5:158-164. 4. Ben-AmarA.NordenbergD, Uberman R, FisherJ. Gorfil C. The control of marginal microleakage in amalgamrestora-
IFiepre 5. 4-META Adhesive; minimalto no microleakage.
44
Addition of Fresh to Existing Amalgam
12. Atsuta M. Abell AK. Turner DT. Nakabayashi N. Takeyama M. A new coupling agent for composite materials. 4-META.
Figure 6.ClearlX New Bond: minimal microleakage.
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11.
tions using a dentin adhesive. A pilot study. Dent Mater 1987; 3:94-96. Shimizu A, Ui T, Kawakami M. Microleakage of amalgam restorations with adhesiveresin cement lining, glass ionomer cement base and fluoride treatment. Dent Mater 1987: 6:64-69. Yu X Y , Wei G, Xu J W .Experimental use of bonding agent to reduce marginal microleakage tests. Quintessence lnt 1987: 18:783-787. Staninec M, Holt M. Bondingof amalgam to tooth structure tensile adhesion and microleakage tests. J Prosthet Dent 1988; 59:397-402. Nakabayashi N. Kojima K, Masuhara E. Studies on dental self curing resins (24).Adhesion to dentin by mechanical Dent M a t Device 1982: 1:74. interlocking. J J a p SOC Swift E J Jr. New adhesive resins. A status report for the American Journal of Dentistry.Am J Dent 1989; 2:358-360. Takeyama M. Kashibuchi N, Nakabayashi N, Masuhara E. Studies on dental self-curing resin ( 17).Adhesion of PMMA with bovine enamel or dental alloys. J J p n Soc Dent Apparatus Mater 1978; 19:179. Nakabayashi N, Takeyama M. Kojima K. Masuhara E. Studies on dental self-curing resins (20).Adhesion mechaDent nism of4-META/MMA-TBB resin to dentin. J J p n SOC Apparatus Mater 1982: 23:34.
J Biomed Mater Res 1982: 16:619. 13. Atsuta M. Nagata K, Turner DT. Strong composites of dimethacwlates with 4-META. J Biomed Mater Res 1983: 17:679. 14. TanakaT. Nagata K. Takeyama M, Nakabayashi N. Masuhara E. Heat treatment of gold alloy to get adhesion with resin. J J p n SOC Apparatus Mater 1980; 21:95. 15. Tanaka T. Nagata K. Takeyama M, Atsuta M, Nakabayashi N. Masuhara E. 4-METAopaqueresin. Anew resin strongly adhesive to nickel chromium alloy. J Dent Res 1981: 60: 1697-1706. 16. Pashley DH, Depew DD. Effects of the smear layer. copalite and oxalate on microleakage. Oper Dent 1986: 11:95-102. 17. Jodaikin A, Austin JC. The effects of cavity smear layer removal on experimental marginal leakage around amalgam restorations. J Dent Res 1981: 60:1861-1866. 18. Barber D, Lyell J. Massler M. Effectiveness of copal resin varnish under amalgam restorations. J F'rosthet Dent 1964: 14:533-536. 19. Lyell J. Barber D, Massler M. Effects of saliva and sulphide solution on the marginal seal of amalgam restorations. J Dent Res 1964; 43:375-379. 20. Swartz ML. Phillips RW. In vitro studies on the marginal leakage of restorative materials. J Am Dent Assoc 1961: 62: 141- 151. 21. Fanian F. Hadavi F, Asgar K. Marginal leakage of dental amalgams. Effects of cavity varnish and burnishing. Can Dent Assoc J 1984; 50:484487. 22. Smith GA, Wilson NHF, Combe EC. Microleakageofconventional and ternary amalgam restorations in vitro. Br Dent J 1978: 144~69-73. 23. Powel GL, Daines DT. Solubility of cavity varnish: a study in vitro. Oper Dent 1987; 12:48-52. 24. Kirk EEJ. Amalgam to amalgam bond, a p r e l i m i n q report. Dent Pract 1962; 12:371. 25. Terkla LG. Mahler DB, Mitchem JG. Bond strength of repaired amalgam. J Prosthet Dent 1961; 11:942-947. 26. Wilson NHF. Smith GA. The in vitro behavior of a cavity liner under amalgam restorations. Br Dent J 1978 145331-334. 27. Andrews JT, Hembree J H . Marginal leakage of amalgam alloys with high content ofcopper: a laboratory study. Oper Dent 1980; 5:7-10.
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