Dent Mater 8:27-30, January, 1992
Microleakage comparison of dentin bonding systems with glass ionomer A~A.Chohayeb Howard University, College of Dentistry, Washington, DC USA
Abstract. Glass-ionomer cements have been suggested as substitutes for dentin-bonded composites. This investigation was designed to compare microleakage of glass-ionomer restorations with that of dentin-bonded composite restorations. Eighty extracted human molars were used in this study. Class V cavities were prepared on the mesial and distal surfaces of each tooth. The distal cavities were restored with Ketac-Fil Glass Ionomer (ESPE). The mesial cavities were divided into four groups and treated with four different dentin bonding systems: Gluma (Columbus Dental), Tenure (two-part powder system; second version, Den-Mat), Scotchbond 2 (3M), and an experimental ferric oxalate system. The commercial materials were placed according to the manufacturers' instructions. The teeth were then thermocycled 3800 cycles between 5°C and 55°C, subjected to silver nitrate staining, and sectioned for microleakage evaluation by three evaluators on a scale of 0 to 4. The ferric oxalate system exhibited significantly less microleakage (median score = 1; Wilcoxon paired testing, p = 0.01) than the glass ionomer (median score = 3). The other dentin bonding systems were similar in microleakage to the glass ionomer (median score = 3). Glass-ionomer cements are reported to have the capacity to adhere to both dentin and enamel (ADA Council on Dental Materials and Devices, 1979). McLean and Wilson (1977) stated that glass-ionomer cements showed promise in certain cervical restorations. McLean et al. (1985) suggested that the use of glass ionomers as cavity liners was a superior procedure when compared with use of a resin/dentin bonding agent to avert marginal leakage under a composite. Leinfelder (1986) also suggested that glass-ionomer cements can be used as a possible substitute for dentin bonding agents because these cements possess thermal expansion coefficients similar to those of tooth structure. A recent study by Leary et al. (1989) stated that the most effective method of reducing microleakage was by the incorporation of glass ionomers as a liner or a base. On the other hand, Crim and Shay (1987) concluded that KetacBond glass-ionomer liner was ineffective in resisting microleakage. The purpose ofthis investigation was to compare the amounts of microleakage of a glass-ionomer cement to selected dentin bonding systems in Class V restorations. MATERIALS AND METHODS The bonding systems used in this study were Tenure (Den-Mat Corp., Santa Maria, CA), Gluma (Columbus Dental, St. Louis, MO), Scotchbond 2 (3M, St. Paul, MN), and an experimental dentin-enamel adhesive based on 6.8% (w/w) ferric oxalate in 2.5% nitric acid, NPG (n-phenylglycine 10% in acetone), and
PMDM (the addition reaction product of pyromellitic dianhydride and 2-hydroxyethyl methacrylate 5% in acetone) (Bowen and Cobb, 1983). Ketac-Fil(ESPE-Premier, Norristown, PA) was the glass-ionomer cement tested. Class V cavities were prepared on both the mesial and distal surfaces of 80 caries-free, freshly extracted human molars. The cavities were prepared at the cemento-enameljunction, so that half the cavity was in enamel and half in dentin. The cavity preparations were cut with a water-cooled high-speed handpiece with round diamond bur #801-023. The depth of the cavity was 2.5 mm, and the width was approximately 3.5 mm. No intentional bevels or undercuts for retention were placed. All the mesial cavities were restored with a microfill resin composite (Silux, 3M, St. Paul, MN) placed over the selected dentin bonding agents. The distal cavities of all teeth were restored with Ketac-Fil glass ionomer, and, as per the manufacturer's instructions, the cavities were treated with Durelon liquid (Premier, Norristown, PA) for 5 s, rinsed for 60 s with distilled water, and dried with air. The glass-ionomer capsules were activated and mixed in a Vari-Mix II triturator (L.D. Caulk Co., Milford, DE) for 10 s. The mixed cement was then placed in the cavity preparations and held in position with light finger pressure over a celluloid strip adapted to the tooth. The matrix was removed after 10 min. The teeth were randomly divided into four groups of 20 each. In group I, the mesial cavities were treated with Scotchbond 2 before being restored with composite. In group II, the mesial cavities were treated with Tenure. In group III, the mesial cavities were treated with the ferric oxalate bonding system. In group IV, the mesial cavities were treated with the Gluma bonding system. The restored teeth were stored at 37°C and 100% humidity for 24 h to simulate clinical conditions. The restorations were then contoured and polished with Sof-Lex discs (3M, St. Paul, MN). The occlusal surface and the apical end of each tooth were sealed with compound. The entire tooth was then coated with three layers of nail polish so that only the margins of the restorations were exposed. The teeth were thermocycled for 7 d, 540 cycles per day, between water baths maintained at 5°C and 55°C. They were then subjected to silver nitrate staining (Wu and Cobb, 1981). After the teeth were stained, they were cut saggitally with a water-cooled diamond circular saw 0.4 mm thick (Isomet, Buehler Ltd., Lake Bluff, IL) for microleakage examination. The restorations were small enough in size so that only one serial section was adequate for proper evaluation of the degree of microleakage. The restorations lost during thermocycling and those containing obvious material voids were discarded. The microleakage was scored on a scale of 0-4:0 = no
Dental Materials~January 1992 27
Table 1 : COMPARISON OF MICROLEAKAGE BETWEEN DENTIN BONDING AGENTS AND GLASS IONOMER CEMENTS Number of Restorations Grouo I+
Grouo II+
Group III#
Grouo IV+
Leakage Score*
Scotchbond 2
Ketac-Fil
Tenure
Ketac-Fil
Ferric Oxalate
Ketac-Fil
Gluma
Ketac-Fil
0.0
4
0
1
1
3
1
2
0
0.2
0
1
0
0
1
0
0
0
0.4
0
1
0
0
1
1
0
0
0.6
0
0
0
1
0
0
1
0
0.8
0
0
0
2
2
0
0
1
1.0
0
1
0
1
2
0
2
1
1.2
0
0
1
0
1
0
0
0
1.4
1
0
0
0
0
0
0
0
1.6
1
1
0
1
5
1
0
1
1.8
0
2
0
0
1
1
0
1
2.0
0
1
1
1
1
1
2
0
2.2
0
0
3
0
0
0
0
1
2.4
2
1
2
2
0
2
0
0
2.6
0
0
2
1
1
1
4
0
2.8
0
2
1
1
0
2
0
0
3.0
4
4
2
1
0
3
1
4
3.2
0
2
1
1
0
0
0
2
3.4
0
1
0
2
0
2
0
0
3.6
1
1
2
1
0
1
0
3
3.8
1
0
0
1
0
2
0
0
4.0
6
2
3
2
0
0
3
1
*Scores were determined on a scale of 0 (no leakage) to 4 (most severe leakage). Wilcoxon signed-ranks analysis indicated: ÷ no difference at 0.01 significant level for Groups I, II and IV; # statistically significant difference at 0.01 level
leakage, 1 = slight gingival margin penetration, 2 = penetration of the stain to the axial wall, 3 = axial wall partially covered by the stain, and 4 = leakage over the entire axial wall. The microleakage at the interface between the tested materials and the cavity wall in both sides of the sectioned tooth was evaluated blindly and separately by three evaluators with a stereozoom microscope at x50 magnification, and the scores were averaged. RESULTS
The average values for each restoration are given in Table 1. Group I compared Scotchbond 2 with the glass-ionomer control material (Table 1). The results of the microleakage evaluations of the Scotchbond 2 showed that 32 observations resulted in microleakage scores of 0, three scores of 1, five scores of 2, four scores of 3, and 56 scores of 4. Opposing glass-ionomer controls showed six observations with scores of 0, 10 scores of 1, 18 scores of 2, 45 scores of 3, and 21 scores of 4. The median score
28 Chohayeb/Microleakage;glass-ionomer/dentinbonding systems
for Scotchbond 2 was 4, while the median score for the glassionomer was 3. Statistical comparison by the Wilcoxon signedranks test for distribution-free analysis (Daniel, 1978) indicated no differences between the two materials at the 0.10 significance level. Group II compared Tenure with the glass-ionomer control material (Table 1). The microleakage evaluations resulted in seven observations with scores of 0, six with scores of 1, 29 with scores of 2, 23 with scores of 3, and 35 with scores of 4. The glass-ionomer controls' evaluations resulted in 20 observations with scores of 0, seven with scores of 1, 16 with scores of 2, 27 with scores of 3, and 30 with scores of 4. Both Tenure and the glass ionomer had median scores of 3. Paired analysis of the data indicated no statistical difference between the materials. Group III compared the experimental ferric oxalate material with the glass-ionomer control (Table 1). Evaluation of the microleakage resulted in 24 observations with scores of 0, 41 with scores of 1, 26 with scores of 2, three with scores of 3, and
TABLE 2: COMPARISON OF MICROLEAKAGE SCORES BETWEEN THE KETAC-FIL GLASS-IONOMER MATERIAL USED IN EACH OF THE FOUR TRIALS Leakage*
Group I
Group II
Group III
Group IV
ences between any of the groups at a 0.10 significance level (Table 2). The median score for all four groups was 3. DISCUSSION
Comparison of the results of microleakage testing has been difficult because of the lack of a consistent control material. This study assessed the possibility ofutilizing glass-ionomer filling material as a control in each study specimen. Results in each group of test specimens demonstrated consistency in the glass- ionomer restorations, verifying that test conditions in each adhesive material group were constant. The results ofthis study showed that the commercial bonding systems and the glass-ionomer cement used exhibited similar microleakage tendencies. Hembree and Andrews (1978), who used a different type of glass ionomer (Aspa, Amalgamated Dental, England), reported that there was no marginal leakage at the experimental periods of one day, three months, or six months. However, at the end of a year, half of the restorations revealed some evidence of leakage. On the other hand, Wenner et al. (1988) stated that, under the conditions of their study, fewer composite specimens revealed microleakage into dentin than either amalgam or glass-ionomer restorations. This is in contrast to the findings of this study, in view of the fact that Wenner et al. (1988) used the same glass-ionomer cement as used in this research. In summary, the glass-ionomer material exhibited reproducible microleakage and could be used as a control in the evaluation of dental adhesive materials.
0.0
0
1
1
0
0.2
1
0
0
0
0.4
1
0
1
0
0.6
0
1
0
0
0.8
0
2
0
1
1.0
1
1
0
1
1.2
0
0
0
0
1.4
0
0
0
0
1.6
1
1
1
1
1.8
2
0
1
1
2.0
1
1
1
0
2.2
0
0
0
1
2.4
1
2
2
0
2.6
0
1
1
0
2.8
2
1
2
0
3.0
4
1
3
4
3.2
2
1
0
2
3.4
1
2
2
0
3.6
1
1
1
3
The author would like to thank Dr. Frederick Eichmiller, American Dental Association Health Foundation, Paffenbarger Research Center, National Institute of Standards and Technology, Gaithersburg, MD, for his assistance with data analysis and manuscript preparation.
3,8
0
1
2
0
ReceivedNovember16, 1990/ AcceptedJune 17, 1991
4.0
2
2
0
1
* [Scores were determined on a scale of 0 (no leakage) to 4 (most severe leakage). + Distribution-freeanalysis(NBSHandbook91)indicatednodifferencebetween groups at the 0.10 significance level.]
one observation with a score of 4. Glass ionomer resulted in seven observations with scores of 0, another seven with scores of 1, 22 with scores of 2, 41 with scores of 3, and 18 observations with scores of 4. The median score of the bonding system was 1, while the median score for the glass ionomer was 3. Wilcoxon paired ranking analysis indicated a significant difference between the experimental bonding system and the glass-ionomer control at a significance level of 0.01. Group IV compared Gluma with the glass-ionomer control material (Table 1). Microleakage evaluation resulted in 15 observations with scores of 0, 11 scores of 1, 18 scores of 2, 25 with scores of 3, and 27 scores of 4. In this group, the glass ionomer resulted in two observations with scores of 0, 12 with scores of 1, 10 with scores of 2, 56 with scores of 3, and 16 observations with scores of 4. The median score for both the Gluma and the glass ionomer was 3. Paired analysis ofthe data indicated no statistically significant difference between the materials. Comparison of the glass-ionomer materials from all pairs by distribution-free analysis (Natrella, 1966) indicated no differ-
ACKNOWLEDGMENT
Addresscorrespondenceand reprint requeststo: A.A.Chohayeb HowardUniversityCollegeofDentistry Box 136 600 WStreet, NW Washington,DC20059 REFERENCES
ADA Council on Dental Materials and Devices (1979): Status report on glass ionomer cements. J A m Dent Assoc 99:221. Bowen RL, Cobb EN (1983). A method for bonding to dentin and enamel. J A m Dent Assoc 107:733-736. Crim GA, Shay JS (1987). Microleakage pattern of a resin veneered glass ionomer cavity liner. JProsthet Dent 58:273276. Daniel WW (1978). Applied nonparametric statistics, National Bureau of Standards Handbook 91. Library of Congress Catalog Card Number:63-0072. Washington, DC, 2-13.4. Hembree JH, Andrews JT (1978). Microleakage of several class V anterior restorative materials: a laboratory study. J A m Dent Assoc 97:179-183. Leary R, Kilgus G, Leinfelder KF (1989). In vitro microleakage ofglass ionomer and dentin bonding agents (abstract). JDent Res 68:187.
Dental Materials~January 1992 29
Leinfelder KF (1986). Efficiency of dentin bonding agents. Part II. A comparison of glass ionomer cement with dentin bonding agents. J A m Dent Assoc 70:15-22. McLean JW, Powis DR, Prosser HJ, Wilson AD (1985). The use of glass ionomer cements in bonding composite resins to dentin. Br Dent J 158:410-414. McLean JW, Wilson AD (1977). The clinical developmentofthe glass ionomer cement. II. Some clinical applications. Aust Dent J 22:120-127.
30 Chohayeb/Microleakage;glass-ionomer/dentinbonding systems
Natrella MG (1966). Experimental statistics. Handbook 91. United States Department of Commerce, National Bureau of Standards. Wenner KK, Fairhurst CW, Morris CF, Hawkins IK, Ringle RD (1988). Microleakage of root restorations. J A m DentAssoc 117:825-828. Wu W, Cobb EN (1981). A silver staining technique for investigating wear of restorative dental composites. J Biomed Mater Res 15:343-348.
Microleakage comparison of dentin bonding systems with glass ionomer A~A.Chohayeb Howard University, College of Dentistry, Washington, DC USA
Abstract. Glass-ionomer cements have been suggested as substitutes for dentin-bonded composites. This investigation was designed to compare microleakage of glass-ionomer restorations with that of dentin-bonded composite restorations. Eighty extracted human molars were used in this study. Class V cavities were prepared on the mesial and distal surfaces of each tooth. The distal cavities were restored with Ketac-Fil Glass Ionomer (ESPE). The mesial cavities were divided into four groups and treated with four different dentin bonding systems: Gluma (Columbus Dental), Tenure (two-part powder system; second version, Den-Mat), Scotchbond 2 (3M), and an experimental ferric oxalate system. The commercial materials were placed according to the manufacturers' instructions. The teeth were then thermocycled 3800 cycles between 5°C and 55°C, subjected to silver nitrate staining, and sectioned for microleakage evaluation by three evaluators on a scale of 0 to 4. The ferric oxalate system exhibited significantly less microleakage (median score = 1; Wilcoxon paired testing, p = 0.01) than the glass ionomer (median score = 3). The other dentin bonding systems were similar in microleakage to the glass ionomer (median score = 3). Glass-ionomer cements are reported to have the capacity to adhere to both dentin and enamel (ADA Council on Dental Materials and Devices, 1979). McLean and Wilson (1977) stated that glass-ionomer cements showed promise in certain cervical restorations. McLean et al. (1985) suggested that the use of glass ionomers as cavity liners was a superior procedure when compared with use of a resin/dentin bonding agent to avert marginal leakage under a composite. Leinfelder (1986) also suggested that glass-ionomer cements can be used as a possible substitute for dentin bonding agents because these cements possess thermal expansion coefficients similar to those of tooth structure. A recent study by Leary et al. (1989) stated that the most effective method of reducing microleakage was by the incorporation of glass ionomers as a liner or a base. On the other hand, Crim and Shay (1987) concluded that KetacBond glass-ionomer liner was ineffective in resisting microleakage. The purpose ofthis investigation was to compare the amounts of microleakage of a glass-ionomer cement to selected dentin bonding systems in Class V restorations. MATERIALS AND METHODS The bonding systems used in this study were Tenure (Den-Mat Corp., Santa Maria, CA), Gluma (Columbus Dental, St. Louis, MO), Scotchbond 2 (3M, St. Paul, MN), and an experimental dentin-enamel adhesive based on 6.8% (w/w) ferric oxalate in 2.5% nitric acid, NPG (n-phenylglycine 10% in acetone), and
PMDM (the addition reaction product of pyromellitic dianhydride and 2-hydroxyethyl methacrylate 5% in acetone) (Bowen and Cobb, 1983). Ketac-Fil(ESPE-Premier, Norristown, PA) was the glass-ionomer cement tested. Class V cavities were prepared on both the mesial and distal surfaces of 80 caries-free, freshly extracted human molars. The cavities were prepared at the cemento-enameljunction, so that half the cavity was in enamel and half in dentin. The cavity preparations were cut with a water-cooled high-speed handpiece with round diamond bur #801-023. The depth of the cavity was 2.5 mm, and the width was approximately 3.5 mm. No intentional bevels or undercuts for retention were placed. All the mesial cavities were restored with a microfill resin composite (Silux, 3M, St. Paul, MN) placed over the selected dentin bonding agents. The distal cavities of all teeth were restored with Ketac-Fil glass ionomer, and, as per the manufacturer's instructions, the cavities were treated with Durelon liquid (Premier, Norristown, PA) for 5 s, rinsed for 60 s with distilled water, and dried with air. The glass-ionomer capsules were activated and mixed in a Vari-Mix II triturator (L.D. Caulk Co., Milford, DE) for 10 s. The mixed cement was then placed in the cavity preparations and held in position with light finger pressure over a celluloid strip adapted to the tooth. The matrix was removed after 10 min. The teeth were randomly divided into four groups of 20 each. In group I, the mesial cavities were treated with Scotchbond 2 before being restored with composite. In group II, the mesial cavities were treated with Tenure. In group III, the mesial cavities were treated with the ferric oxalate bonding system. In group IV, the mesial cavities were treated with the Gluma bonding system. The restored teeth were stored at 37°C and 100% humidity for 24 h to simulate clinical conditions. The restorations were then contoured and polished with Sof-Lex discs (3M, St. Paul, MN). The occlusal surface and the apical end of each tooth were sealed with compound. The entire tooth was then coated with three layers of nail polish so that only the margins of the restorations were exposed. The teeth were thermocycled for 7 d, 540 cycles per day, between water baths maintained at 5°C and 55°C. They were then subjected to silver nitrate staining (Wu and Cobb, 1981). After the teeth were stained, they were cut saggitally with a water-cooled diamond circular saw 0.4 mm thick (Isomet, Buehler Ltd., Lake Bluff, IL) for microleakage examination. The restorations were small enough in size so that only one serial section was adequate for proper evaluation of the degree of microleakage. The restorations lost during thermocycling and those containing obvious material voids were discarded. The microleakage was scored on a scale of 0-4:0 = no
Dental Materials~January 1992 27
Table 1 : COMPARISON OF MICROLEAKAGE BETWEEN DENTIN BONDING AGENTS AND GLASS IONOMER CEMENTS Number of Restorations Grouo I+
Grouo II+
Group III#
Grouo IV+
Leakage Score*
Scotchbond 2
Ketac-Fil
Tenure
Ketac-Fil
Ferric Oxalate
Ketac-Fil
Gluma
Ketac-Fil
0.0
4
0
1
1
3
1
2
0
0.2
0
1
0
0
1
0
0
0
0.4
0
1
0
0
1
1
0
0
0.6
0
0
0
1
0
0
1
0
0.8
0
0
0
2
2
0
0
1
1.0
0
1
0
1
2
0
2
1
1.2
0
0
1
0
1
0
0
0
1.4
1
0
0
0
0
0
0
0
1.6
1
1
0
1
5
1
0
1
1.8
0
2
0
0
1
1
0
1
2.0
0
1
1
1
1
1
2
0
2.2
0
0
3
0
0
0
0
1
2.4
2
1
2
2
0
2
0
0
2.6
0
0
2
1
1
1
4
0
2.8
0
2
1
1
0
2
0
0
3.0
4
4
2
1
0
3
1
4
3.2
0
2
1
1
0
0
0
2
3.4
0
1
0
2
0
2
0
0
3.6
1
1
2
1
0
1
0
3
3.8
1
0
0
1
0
2
0
0
4.0
6
2
3
2
0
0
3
1
*Scores were determined on a scale of 0 (no leakage) to 4 (most severe leakage). Wilcoxon signed-ranks analysis indicated: ÷ no difference at 0.01 significant level for Groups I, II and IV; # statistically significant difference at 0.01 level
leakage, 1 = slight gingival margin penetration, 2 = penetration of the stain to the axial wall, 3 = axial wall partially covered by the stain, and 4 = leakage over the entire axial wall. The microleakage at the interface between the tested materials and the cavity wall in both sides of the sectioned tooth was evaluated blindly and separately by three evaluators with a stereozoom microscope at x50 magnification, and the scores were averaged. RESULTS
The average values for each restoration are given in Table 1. Group I compared Scotchbond 2 with the glass-ionomer control material (Table 1). The results of the microleakage evaluations of the Scotchbond 2 showed that 32 observations resulted in microleakage scores of 0, three scores of 1, five scores of 2, four scores of 3, and 56 scores of 4. Opposing glass-ionomer controls showed six observations with scores of 0, 10 scores of 1, 18 scores of 2, 45 scores of 3, and 21 scores of 4. The median score
28 Chohayeb/Microleakage;glass-ionomer/dentinbonding systems
for Scotchbond 2 was 4, while the median score for the glassionomer was 3. Statistical comparison by the Wilcoxon signedranks test for distribution-free analysis (Daniel, 1978) indicated no differences between the two materials at the 0.10 significance level. Group II compared Tenure with the glass-ionomer control material (Table 1). The microleakage evaluations resulted in seven observations with scores of 0, six with scores of 1, 29 with scores of 2, 23 with scores of 3, and 35 with scores of 4. The glass-ionomer controls' evaluations resulted in 20 observations with scores of 0, seven with scores of 1, 16 with scores of 2, 27 with scores of 3, and 30 with scores of 4. Both Tenure and the glass ionomer had median scores of 3. Paired analysis of the data indicated no statistical difference between the materials. Group III compared the experimental ferric oxalate material with the glass-ionomer control (Table 1). Evaluation of the microleakage resulted in 24 observations with scores of 0, 41 with scores of 1, 26 with scores of 2, three with scores of 3, and
TABLE 2: COMPARISON OF MICROLEAKAGE SCORES BETWEEN THE KETAC-FIL GLASS-IONOMER MATERIAL USED IN EACH OF THE FOUR TRIALS Leakage*
Group I
Group II
Group III
Group IV
ences between any of the groups at a 0.10 significance level (Table 2). The median score for all four groups was 3. DISCUSSION
Comparison of the results of microleakage testing has been difficult because of the lack of a consistent control material. This study assessed the possibility ofutilizing glass-ionomer filling material as a control in each study specimen. Results in each group of test specimens demonstrated consistency in the glass- ionomer restorations, verifying that test conditions in each adhesive material group were constant. The results ofthis study showed that the commercial bonding systems and the glass-ionomer cement used exhibited similar microleakage tendencies. Hembree and Andrews (1978), who used a different type of glass ionomer (Aspa, Amalgamated Dental, England), reported that there was no marginal leakage at the experimental periods of one day, three months, or six months. However, at the end of a year, half of the restorations revealed some evidence of leakage. On the other hand, Wenner et al. (1988) stated that, under the conditions of their study, fewer composite specimens revealed microleakage into dentin than either amalgam or glass-ionomer restorations. This is in contrast to the findings of this study, in view of the fact that Wenner et al. (1988) used the same glass-ionomer cement as used in this research. In summary, the glass-ionomer material exhibited reproducible microleakage and could be used as a control in the evaluation of dental adhesive materials.
0.0
0
1
1
0
0.2
1
0
0
0
0.4
1
0
1
0
0.6
0
1
0
0
0.8
0
2
0
1
1.0
1
1
0
1
1.2
0
0
0
0
1.4
0
0
0
0
1.6
1
1
1
1
1.8
2
0
1
1
2.0
1
1
1
0
2.2
0
0
0
1
2.4
1
2
2
0
2.6
0
1
1
0
2.8
2
1
2
0
3.0
4
1
3
4
3.2
2
1
0
2
3.4
1
2
2
0
3.6
1
1
1
3
The author would like to thank Dr. Frederick Eichmiller, American Dental Association Health Foundation, Paffenbarger Research Center, National Institute of Standards and Technology, Gaithersburg, MD, for his assistance with data analysis and manuscript preparation.
3,8
0
1
2
0
ReceivedNovember16, 1990/ AcceptedJune 17, 1991
4.0
2
2
0
1
* [Scores were determined on a scale of 0 (no leakage) to 4 (most severe leakage). + Distribution-freeanalysis(NBSHandbook91)indicatednodifferencebetween groups at the 0.10 significance level.]
one observation with a score of 4. Glass ionomer resulted in seven observations with scores of 0, another seven with scores of 1, 22 with scores of 2, 41 with scores of 3, and 18 observations with scores of 4. The median score of the bonding system was 1, while the median score for the glass ionomer was 3. Wilcoxon paired ranking analysis indicated a significant difference between the experimental bonding system and the glass-ionomer control at a significance level of 0.01. Group IV compared Gluma with the glass-ionomer control material (Table 1). Microleakage evaluation resulted in 15 observations with scores of 0, 11 scores of 1, 18 scores of 2, 25 with scores of 3, and 27 scores of 4. In this group, the glass ionomer resulted in two observations with scores of 0, 12 with scores of 1, 10 with scores of 2, 56 with scores of 3, and 16 observations with scores of 4. The median score for both the Gluma and the glass ionomer was 3. Paired analysis ofthe data indicated no statistically significant difference between the materials. Comparison of the glass-ionomer materials from all pairs by distribution-free analysis (Natrella, 1966) indicated no differ-
ACKNOWLEDGMENT
Addresscorrespondenceand reprint requeststo: A.A.Chohayeb HowardUniversityCollegeofDentistry Box 136 600 WStreet, NW Washington,DC20059 REFERENCES
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30 Chohayeb/Microleakage;glass-ionomer/dentinbonding systems
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