The effect of two smear layer cleansers on shear bond strength to dentin S.L. Wendt, Jr.1 C.A. Jebeles 2 K.F. Leinfelder3
1Graduate student Department of Biomaterials University of Alabama at Birmingham School of Dentistry Birmingham, Alabama 35294; and Assistant Professor of Operative Dentistry Department of Restorative Dentistry and Endodontology University of Connecticut Health Center School of Dental Medicine Farmington, Connecticut 06032 2Dental Student University of Alabama at Birmingham 3Alumni/Volker Professor of Clinical Dentistry and Director Biomaterials Clinical Research Department of Biomaterials University of Alabama at Birmingham Received September 9, 1988
Accepted September 2, 1989 Dent Mater 6:1-4, January, 1990
Abstract- Prevention of microleakage
and post-operative sensitivity depends upon maintenance of the integrity of the bond between the resin composite and the tooth. Removal of the dentinal smear layer allows for better bond strengths for the newer dentinal bonding agents. The purpose of this study was to evaluate the shear bond strengths of a light-cured composite to dentin treated with one proprietary and one experimental cleansing agent. Bond strengths for the teeth cleansed with the experimental cleansing agent were significantly (p < 0.05) greater than bond strengths of teeth cleansed with EDTA.
ne of the problems that has plagued the use of composite restorative materials in dentistry has been the inability to bond the composite to dentin. This inability to bond to dentin, especially at the dentinal or cemental margins of restorations, has been attributed as one cause of clinical microleakage and post-operative sensitivity (Br~innstrSm, 1985). It has also been speculated that this lack of bSnd can lead to marginal gap formation and bacterial leakage onto the floor of the preparation, thus possibly leading to secondary caries formation (Torstenson et al., 1982). It is well-documented that surface layers on enamel and dentin left by cutting with burs must be removed for a strong adhesive bond with dentin to be developed (Bowen et aI., 1984; Soetopo et al., 1978; Asmussen and Munksgaard, 1985). The latest generation of bonding a g e n t s - t h e "third generation", as coined by Retief (1987)-all contain cleansers or mordants for removal or modification of the dentinal smear layer. Some are more effective than others in totally removing the dentinal smear layer, with or without a scrubbing of the dentin. The purpose of this study was to evaluate the shear bond strengths of a light-cured composite to dentin treated with one proprietary and one experimental cleansing agent.
O
MATERIALS AND METHODS
Occlusin resin composite (ICI, England; distributed by Coe, Chicago, IL) was bonded to the dentin of 200 teeth by use of the Gluma Dentinal Bonding System (Bayer Pharmaceuticals, West Germany; distributed by Columbus Dental, St. Louis, MO). Two different cleansers were used for the removal of the dentinal smear layer: the 0.5 M EDTA cleanser supplied with Gluma and an experimental 1:1 polyacrylic/maleic acid solution (25
wt%) (BisCo, Lombard, IL). All of the teeth were prepared by removal of the smear layer and bonded with the composite test cylinder. The teeth were stored in de-ionized water for a specified time period, thermocycled where indicated, and tested for shear bond strengths in an Instron Universal testing machine (Instron, Canton, MA). Two hundred maxillary molars were collected, f'Lxed in formalin for three days, rinsed, and stored in deionized water. The average length of storage of the teeth before testing was six months. The enamel, mesial, proximal surface of each tooth was removed in a model trimmer to just within the dentino-enamel junction. The roots were removed and the rest of the clinical crown cut to form a block of dentin measuring approximately 5 x 5 millimeters. Each block of dentin was mounted in a brass tooth cup with fast-set self-curing acrylic resin so that the mesial proximal surface of dentin was parallel and raised above the edges of the tooth cup. The tooth cup was mounted in a brass block milling device. The surface of the dentin block was ground fiat with wet 600-grit c a r b o r u n d u m paper on a r o t a r y wheel. The surface of the dentin block was left well above the level of the acrylic resin to ensure that during surfacing there was no contamination to interfere with the bonding process. The dentin surface was rinsed in running water and received a 40-second scrub with either the proprietary EDTA (Gluma Cleanser) or the experimental polyacrylic/maleic acid cleansing agent (see Table 1). In this study, the experimental design was limited to the same cleansing time for both the cleansers to eliminate an experimental variable. A previous study (Berry et al., 1987) indicates that cleansing times of from 5 to 30 s are equally effective in re-
Dental Materials~January 1990
1
TABLE 1 EXPERIMENTALDESIGN Groups
N 20
Treatment 15 min of storage in de-ionized water at 37° _+ 1°C 24ohour storage in de-ionized water at 37° -- 1°0 24-hour storage in de-ionized water at 37° _+ 1°0 + Thermocycle One-month storage in de-ionized water at 37°0 __ 1°C One-month storage in de-ionized water at 37° __ 1°C + Thermocycle
A 20 20 B 20 20 C 20 20 D 20 20 E 20
moving the smear layer with polyacrylic acid. The teeth were rinsed in running water for 20 s and dried in clean oilfree air. Gluma bonding agent was applied and allowed to set for 60 s. The excess bonding agent was then removed by the air-drying of the teeth thoroughly with clean, oil-free air from a surgical bulb syringe. The tooth cup was mounted in a modified dentinal bonding apparatus after Retief (O'Brien et al., 1987). The composite was inserted into the mold in two increments, each cured by visible light for 60 s. This process formed a cylinder of composite 3.5 mm in diameter and 6 mm in height perpendicular to the flat surface of the dentin. The samples were divided into five s u b g r o u p s a c c o r d i n g to dentin cleansing agent. Group A teeth were stored in de-ionized water at 37°_+ 1°C for 15 min. Groups B and C were stored for 24 h in de-ionized water. Group C samples were additionally thermocycled in water baths of 8°C
Cleansers EDTA (GIumaCleanser) Potyacrylic/maleic acid EDTA (GlumaCleanser) Polyacrylic/maleic acid EDTA (Gluma Cleanser) Polyacrylic/maleic acid EDTA (GlumaCleanser) Polyacrylic maleic acid EDTA (GlumaCleanser) Polyacrylic/maleic acid
and 50°C for 250 complete cycles, with a dwell time of 15 s. Groups D and E were stored for one month in deionized water, and Group E was thermocycled as in Group C. A knifeedged rod was affLxed in the crosshead. The tooth cup was positioned in a block perpendicular to the rod on the platten of the load cell. The specimens were tested to fracture in the testing machine (Instron Universal, Canton, MA). A cross-head speed of 0.5 mm per min was used. The d a t a w e r e s u b j e c t e d to an Analysis of Variance (ANOVA). The percentage of resin composite material left on the bonding site was estimated in increments of 5% by utilization of a stereo microscope. An ANOVA and regression plot for each of the groups were made for testing of correlation of bond strength to percent of resin composite left after debonding. Ten human premolar extracted teeth were prepared with a MOD slot preparation 2 mm wide and 3 mm in depth, by utilization of a number 245
TABLE 2
BOND STRENGTHSOF COMPOSITETO DENTIN Group A B C D E
2
Cleanser EDTA P/M ACID EDTA P/M ACID EDTA P/M ACID EDTA P/M ACID EDTA P/M ACID
Bond Strength (MPa) Mean (s.d.) 2.79 (_ 1.64) 4.69 (+ 2.68) 4.65 (+ 3.43) 4.72 (-,- 2.82) 4.10 (_ 2.26) 6.10 (_+ 3.48) 4.06 (__ 2.41) 7.28 (_+ 3.94) 6.33 (-+- 6.00) 9.36 (-+ 5.68)
Significance S (p
1Graduate student Department of Biomaterials University of Alabama at Birmingham School of Dentistry Birmingham, Alabama 35294; and Assistant Professor of Operative Dentistry Department of Restorative Dentistry and Endodontology University of Connecticut Health Center School of Dental Medicine Farmington, Connecticut 06032 2Dental Student University of Alabama at Birmingham 3Alumni/Volker Professor of Clinical Dentistry and Director Biomaterials Clinical Research Department of Biomaterials University of Alabama at Birmingham Received September 9, 1988
Accepted September 2, 1989 Dent Mater 6:1-4, January, 1990
Abstract- Prevention of microleakage
and post-operative sensitivity depends upon maintenance of the integrity of the bond between the resin composite and the tooth. Removal of the dentinal smear layer allows for better bond strengths for the newer dentinal bonding agents. The purpose of this study was to evaluate the shear bond strengths of a light-cured composite to dentin treated with one proprietary and one experimental cleansing agent. Bond strengths for the teeth cleansed with the experimental cleansing agent were significantly (p < 0.05) greater than bond strengths of teeth cleansed with EDTA.
ne of the problems that has plagued the use of composite restorative materials in dentistry has been the inability to bond the composite to dentin. This inability to bond to dentin, especially at the dentinal or cemental margins of restorations, has been attributed as one cause of clinical microleakage and post-operative sensitivity (Br~innstrSm, 1985). It has also been speculated that this lack of bSnd can lead to marginal gap formation and bacterial leakage onto the floor of the preparation, thus possibly leading to secondary caries formation (Torstenson et al., 1982). It is well-documented that surface layers on enamel and dentin left by cutting with burs must be removed for a strong adhesive bond with dentin to be developed (Bowen et aI., 1984; Soetopo et al., 1978; Asmussen and Munksgaard, 1985). The latest generation of bonding a g e n t s - t h e "third generation", as coined by Retief (1987)-all contain cleansers or mordants for removal or modification of the dentinal smear layer. Some are more effective than others in totally removing the dentinal smear layer, with or without a scrubbing of the dentin. The purpose of this study was to evaluate the shear bond strengths of a light-cured composite to dentin treated with one proprietary and one experimental cleansing agent.
O
MATERIALS AND METHODS
Occlusin resin composite (ICI, England; distributed by Coe, Chicago, IL) was bonded to the dentin of 200 teeth by use of the Gluma Dentinal Bonding System (Bayer Pharmaceuticals, West Germany; distributed by Columbus Dental, St. Louis, MO). Two different cleansers were used for the removal of the dentinal smear layer: the 0.5 M EDTA cleanser supplied with Gluma and an experimental 1:1 polyacrylic/maleic acid solution (25
wt%) (BisCo, Lombard, IL). All of the teeth were prepared by removal of the smear layer and bonded with the composite test cylinder. The teeth were stored in de-ionized water for a specified time period, thermocycled where indicated, and tested for shear bond strengths in an Instron Universal testing machine (Instron, Canton, MA). Two hundred maxillary molars were collected, f'Lxed in formalin for three days, rinsed, and stored in deionized water. The average length of storage of the teeth before testing was six months. The enamel, mesial, proximal surface of each tooth was removed in a model trimmer to just within the dentino-enamel junction. The roots were removed and the rest of the clinical crown cut to form a block of dentin measuring approximately 5 x 5 millimeters. Each block of dentin was mounted in a brass tooth cup with fast-set self-curing acrylic resin so that the mesial proximal surface of dentin was parallel and raised above the edges of the tooth cup. The tooth cup was mounted in a brass block milling device. The surface of the dentin block was ground fiat with wet 600-grit c a r b o r u n d u m paper on a r o t a r y wheel. The surface of the dentin block was left well above the level of the acrylic resin to ensure that during surfacing there was no contamination to interfere with the bonding process. The dentin surface was rinsed in running water and received a 40-second scrub with either the proprietary EDTA (Gluma Cleanser) or the experimental polyacrylic/maleic acid cleansing agent (see Table 1). In this study, the experimental design was limited to the same cleansing time for both the cleansers to eliminate an experimental variable. A previous study (Berry et al., 1987) indicates that cleansing times of from 5 to 30 s are equally effective in re-
Dental Materials~January 1990
1
TABLE 1 EXPERIMENTALDESIGN Groups
N 20
Treatment 15 min of storage in de-ionized water at 37° _+ 1°C 24ohour storage in de-ionized water at 37° -- 1°0 24-hour storage in de-ionized water at 37° _+ 1°0 + Thermocycle One-month storage in de-ionized water at 37°0 __ 1°C One-month storage in de-ionized water at 37° __ 1°C + Thermocycle
A 20 20 B 20 20 C 20 20 D 20 20 E 20
moving the smear layer with polyacrylic acid. The teeth were rinsed in running water for 20 s and dried in clean oilfree air. Gluma bonding agent was applied and allowed to set for 60 s. The excess bonding agent was then removed by the air-drying of the teeth thoroughly with clean, oil-free air from a surgical bulb syringe. The tooth cup was mounted in a modified dentinal bonding apparatus after Retief (O'Brien et al., 1987). The composite was inserted into the mold in two increments, each cured by visible light for 60 s. This process formed a cylinder of composite 3.5 mm in diameter and 6 mm in height perpendicular to the flat surface of the dentin. The samples were divided into five s u b g r o u p s a c c o r d i n g to dentin cleansing agent. Group A teeth were stored in de-ionized water at 37°_+ 1°C for 15 min. Groups B and C were stored for 24 h in de-ionized water. Group C samples were additionally thermocycled in water baths of 8°C
Cleansers EDTA (GIumaCleanser) Potyacrylic/maleic acid EDTA (GlumaCleanser) Polyacrylic/maleic acid EDTA (Gluma Cleanser) Polyacrylic/maleic acid EDTA (GlumaCleanser) Polyacrylic maleic acid EDTA (GlumaCleanser) Polyacrylic/maleic acid
and 50°C for 250 complete cycles, with a dwell time of 15 s. Groups D and E were stored for one month in deionized water, and Group E was thermocycled as in Group C. A knifeedged rod was affLxed in the crosshead. The tooth cup was positioned in a block perpendicular to the rod on the platten of the load cell. The specimens were tested to fracture in the testing machine (Instron Universal, Canton, MA). A cross-head speed of 0.5 mm per min was used. The d a t a w e r e s u b j e c t e d to an Analysis of Variance (ANOVA). The percentage of resin composite material left on the bonding site was estimated in increments of 5% by utilization of a stereo microscope. An ANOVA and regression plot for each of the groups were made for testing of correlation of bond strength to percent of resin composite left after debonding. Ten human premolar extracted teeth were prepared with a MOD slot preparation 2 mm wide and 3 mm in depth, by utilization of a number 245
TABLE 2
BOND STRENGTHSOF COMPOSITETO DENTIN Group A B C D E
2
Cleanser EDTA P/M ACID EDTA P/M ACID EDTA P/M ACID EDTA P/M ACID EDTA P/M ACID
Bond Strength (MPa) Mean (s.d.) 2.79 (_ 1.64) 4.69 (+ 2.68) 4.65 (+ 3.43) 4.72 (-,- 2.82) 4.10 (_ 2.26) 6.10 (_+ 3.48) 4.06 (__ 2.41) 7.28 (_+ 3.94) 6.33 (-+- 6.00) 9.36 (-+ 5.68)
Significance S (p
