Dent Mater 8:370-374, November,1992
Shear bond strengths of ten dentin adhesive systems P. T. Triolo, Jr. 1, E. J. Swift, Jr. 2
ICenter for Clinical Studies, ~Department of Operative Dentistry, College of Dentistry, The University of Iowa, Iowa City, IA, USA
Abstract. This in vitrostudy tested the shear bond strengthsof nine third-generationdentin bondingsystems. All of these systems had higher bond strengths than the control, a second-generation agent. Amalgambond and All-Bond had the strongest bonds to dentin, 23.3 + 5.7 and 19.3 + 5.6 MPa, respectively. Clearfil Photo Bond and Prisma Universal Bond 3 had intermediate bond strengths (approximately 13 MPa). Gluma, PowerBond, Scotchbond 2, Tenure, and XR-Bond all had mean shear bond strengths of less than 8 MPa.
INTRODUCTION One of the major obstacles to strong and stable dentin bonding is the "smear layeF' which covers instrumented dentin surfaces (Cotton, 1984). The smear layer occupies a strategic position in restorative dentistry, the interface of restorative materials with the dentin substrate (Pashley, 1984). Smeared contaminants lower surface energy and therefore affect the reactivity of the surface (Gwinnett, 1984). Removal of the smear layer may optimize adhesion of restorative materials to dentin (Bowen et al., 1984), but some investigators believe that smear layers actually have a protective role (Br/~nnstrSm, 1984). Until recently, most dentin bonding agents did not require smear layer removal. In fact, removal of the smear layer adversely affected the bond strength of some agents (Solomon and Beech, 1985; Ishioka and Caputo, 1989; White et al., 1989). Most of the current, or third-generation, dentin bonding systems either remove or modify the smear layer. In 1982, Bowen et al. reported a technique of treating dentin with a series of reagents to improve bond strengths. "Used in sequence, solutions of an acidic mordant, a surface-active comonomer, and a coupling agent having methacrylate and aromatic carboxyl groups were used to prepare dentin surfaces ... for strong bonding with a composite." Many new dentin bonding systems have been developed for clinical use since Bowen's original work with "oxalate dentin bonding." Studies comparing the bond strengths of third-generation dentin bonding systems have provided conflicting results. Therefore, the purpose of this study was to compare the shear bond strengths of some commercially available dentin adhesive systems in a single in vitro experiment.
MATERIALS AND METHODS One hundred twenty caries-free and unrestored human third molars were obtained and stored for one to six months in distilled water with thymol disinfectant. To expose dentin, the
370 Triolo & Swift~Bond strengths of dentin adhesives
occlusal portion of each tooth was flattened on an orthodontic model trimmer to a depth of 1.5 mm apical to the deepest occlusal pit. The teeth were aligned on a custom mounting platform so that the flattened dentin surface extended 2 mm beyond the surface of the platform. The teeth were mounted in phenolic rings (Buehler, Ltd., Lake Bluff, IL, USA) with chemical-cured acrylic (Fastray, Harry J. Bosworth Co., Skokie, IL, USA), leaving the dentin surface 2 mm above the acrylic. Areas of dentin at least 5 mm in diameter were exposed and hand-polished on wet 320, 400, and 600 grit silicon carbide paper. The samples were cleansed in an ultrasonic distilled water bath for 5 min. Twelve teeth were randomly assigned to each of the ten treatment groups. Dual-Cure Scotchbond, a phosphonate ester dentin/enamel bonding agent, was included as the control. The third-generation dentin adhesives evaluated in this study are listed in Table 1. A hole (4.76 mm diameter) was punched in the center of a strip of adhesive tape, which was burnished onto the dentin surface to limit the flow of reagents and resins. Conditioners, primers, and bonding resins were applied to the dentin surface in strict accordance with manufacturers' directions. All-Bond and PowerBond were used with their respective dentin conditioners rather than the "total-etch" technique. With All-Bond, dentin surfaces were kept slightly moist prior to primer application, as recommended by the manufacturer. Gelatin capsules with an internal diameter of 4.65 mm (Eli Lilly and Company, Indianapolis, IN, USA) were used to make composite posts. A microfilled composite (universal shade Silux Plus, 3M) was placed into the gelatin capsule, slightly overfilling it. The composite-filled capsule was then applied to the dentin surface. A 50 g weight was placed on top of the gelatin capsule to express the excess composite, which was then removed. Leaving the weight in place, the composite material was polymerized by visible light through the gelatin capsule for 2 min. The specimens were stored in 37°C distilled water for 24 h before thermocycling 600 times. The dwell time in each bath (5 and 55 ° ---5°C) was 30 s with an exchange time of 5 s between baths. The samples were then aged for 28 d in 37°C distilled water, with the water being renewed each seventh day. Bond strengths between composite and dentin were measured in the shear mode with a universal testing machine (Instron Corporation, Canton, MA, USA). Specimens w e r e placed in a mounting jig attached to a compression load cell with full scale set at 50 kg. A knife-edge rod was used with a crosshead speed of 0.5 cm/min. Fracture loads were recorded
TABLE 1: COMPOSITIONOF THIRD-GENERATIONDENTINBONDINGSYSTEMSEVALUATEDIN THIS STUDY. (SOURCES: ALBERS, 1990;CLINICALRESEARCHASSOCIATES, 1991;JOHNSON et al., 1991) AdhesiveSystem
Component
Chemical Composition
Batch Number
All-Bond
Conditioner Primer A Primer B D/E BondingResin
SA-HEMA NTG-GMA BPDM Bis-GMA,UDMA, HEMA
029151 069101 069241 069271
Activator AdhesiveAgent Base Catalyst
citric acid, ferric chloride HEMA 4-META, MMA, HEMA tri-butyl borane
10101 030891-364494 10101 10102
Kuraray/J. Morita Tustin,CA, USA
K-Etchant Universal Catalyst
40% phosphoricacid Bis-GMA, HEMA, 10-MDP aromatic compounds
611116 057 611116229 611116 127
Gluma
D/E Conditioner
oxalic acid, AI nitrate, glycine HEMA, glutaraldehyde Bis-GMA
D666/2WJK8500 029187 RZl12 029209 RZ113
Bisco Itasca, IL, USA Amalgambond
Parkell Farmingdale,NY, USA CleaffilPhoto B o n d
Bayer/MilesDental South Bend, IN, USA Prisma UniversalBond3
CaulldDentsply Milford, DE, USA PowerBond
Cosmedent Chicago, IL, USA Scotchbond2
3M Dental Products St. Paul, MN, USA Tenure
Den-Mat Santa Maria, CA, USA XR-BondingSystem
Kerr Romulus,MI, USA
Primer Sealer Primer Adhesive
HEMA, PENTA HEMA, PENTA, urethaneresins
100190
Conditioner Primer A Primer B D/E Adhesive
SA-HEMA NTG-GMA CPDM, TCDM Bis-GMA, UDMA, HEMA
039201 039191 039121 039251
Scotchprep Adhesive
HEMA, maleicacid Bis-GMA, HEMA
P910215 P910215
Conditioner SolutionA SolutionB Visar-Seal
AI oxalate, nitricacid NTG-GMA PMDM Bis-GMA
291050 461040 462060 199026
XR-Primer XR-Bond
phosphateester phosphateester, UDMA
053.47 50.35
121190
Bis-GMA:bisphenolglycidylmethacrylate,BPDM:biphenyldimethacrylate,CPDM:cyclopentaldimethacrylate, HEMA:2-hydroxyethylmethacrylate,NTG-GMA:N-tolylglycine-glycidylmethacrylate,PENTA:phosphonated penta-acrylateester, PMDM:pyromelliticacid diethylmethacrylate,SA-HEMA:succinicacid + hydroxyethyl methacrylate,TCDM:tricyclicdimethacrylate,UDMA:urethanedimethacrylate,4-META:4-methacryloxyethyl trimelliticacid, 10-MDP: 10-methacryloyloxydecyldihydrogenphosphate.
by a strip chart and converted to MPa units using the crosssectional area of the composite posts. Data were analyzed with a one-way analysis of variance (ANOVA) and post hoc Duncan's multiple range test for pairwise contrasts using the SAS statistical software package (SAS Institute, Cary, NC, USA). The significance level was set at p
Shear bond strengths of ten dentin adhesive systems P. T. Triolo, Jr. 1, E. J. Swift, Jr. 2
ICenter for Clinical Studies, ~Department of Operative Dentistry, College of Dentistry, The University of Iowa, Iowa City, IA, USA
Abstract. This in vitrostudy tested the shear bond strengthsof nine third-generationdentin bondingsystems. All of these systems had higher bond strengths than the control, a second-generation agent. Amalgambond and All-Bond had the strongest bonds to dentin, 23.3 + 5.7 and 19.3 + 5.6 MPa, respectively. Clearfil Photo Bond and Prisma Universal Bond 3 had intermediate bond strengths (approximately 13 MPa). Gluma, PowerBond, Scotchbond 2, Tenure, and XR-Bond all had mean shear bond strengths of less than 8 MPa.
INTRODUCTION One of the major obstacles to strong and stable dentin bonding is the "smear layeF' which covers instrumented dentin surfaces (Cotton, 1984). The smear layer occupies a strategic position in restorative dentistry, the interface of restorative materials with the dentin substrate (Pashley, 1984). Smeared contaminants lower surface energy and therefore affect the reactivity of the surface (Gwinnett, 1984). Removal of the smear layer may optimize adhesion of restorative materials to dentin (Bowen et al., 1984), but some investigators believe that smear layers actually have a protective role (Br/~nnstrSm, 1984). Until recently, most dentin bonding agents did not require smear layer removal. In fact, removal of the smear layer adversely affected the bond strength of some agents (Solomon and Beech, 1985; Ishioka and Caputo, 1989; White et al., 1989). Most of the current, or third-generation, dentin bonding systems either remove or modify the smear layer. In 1982, Bowen et al. reported a technique of treating dentin with a series of reagents to improve bond strengths. "Used in sequence, solutions of an acidic mordant, a surface-active comonomer, and a coupling agent having methacrylate and aromatic carboxyl groups were used to prepare dentin surfaces ... for strong bonding with a composite." Many new dentin bonding systems have been developed for clinical use since Bowen's original work with "oxalate dentin bonding." Studies comparing the bond strengths of third-generation dentin bonding systems have provided conflicting results. Therefore, the purpose of this study was to compare the shear bond strengths of some commercially available dentin adhesive systems in a single in vitro experiment.
MATERIALS AND METHODS One hundred twenty caries-free and unrestored human third molars were obtained and stored for one to six months in distilled water with thymol disinfectant. To expose dentin, the
370 Triolo & Swift~Bond strengths of dentin adhesives
occlusal portion of each tooth was flattened on an orthodontic model trimmer to a depth of 1.5 mm apical to the deepest occlusal pit. The teeth were aligned on a custom mounting platform so that the flattened dentin surface extended 2 mm beyond the surface of the platform. The teeth were mounted in phenolic rings (Buehler, Ltd., Lake Bluff, IL, USA) with chemical-cured acrylic (Fastray, Harry J. Bosworth Co., Skokie, IL, USA), leaving the dentin surface 2 mm above the acrylic. Areas of dentin at least 5 mm in diameter were exposed and hand-polished on wet 320, 400, and 600 grit silicon carbide paper. The samples were cleansed in an ultrasonic distilled water bath for 5 min. Twelve teeth were randomly assigned to each of the ten treatment groups. Dual-Cure Scotchbond, a phosphonate ester dentin/enamel bonding agent, was included as the control. The third-generation dentin adhesives evaluated in this study are listed in Table 1. A hole (4.76 mm diameter) was punched in the center of a strip of adhesive tape, which was burnished onto the dentin surface to limit the flow of reagents and resins. Conditioners, primers, and bonding resins were applied to the dentin surface in strict accordance with manufacturers' directions. All-Bond and PowerBond were used with their respective dentin conditioners rather than the "total-etch" technique. With All-Bond, dentin surfaces were kept slightly moist prior to primer application, as recommended by the manufacturer. Gelatin capsules with an internal diameter of 4.65 mm (Eli Lilly and Company, Indianapolis, IN, USA) were used to make composite posts. A microfilled composite (universal shade Silux Plus, 3M) was placed into the gelatin capsule, slightly overfilling it. The composite-filled capsule was then applied to the dentin surface. A 50 g weight was placed on top of the gelatin capsule to express the excess composite, which was then removed. Leaving the weight in place, the composite material was polymerized by visible light through the gelatin capsule for 2 min. The specimens were stored in 37°C distilled water for 24 h before thermocycling 600 times. The dwell time in each bath (5 and 55 ° ---5°C) was 30 s with an exchange time of 5 s between baths. The samples were then aged for 28 d in 37°C distilled water, with the water being renewed each seventh day. Bond strengths between composite and dentin were measured in the shear mode with a universal testing machine (Instron Corporation, Canton, MA, USA). Specimens w e r e placed in a mounting jig attached to a compression load cell with full scale set at 50 kg. A knife-edge rod was used with a crosshead speed of 0.5 cm/min. Fracture loads were recorded
TABLE 1: COMPOSITIONOF THIRD-GENERATIONDENTINBONDINGSYSTEMSEVALUATEDIN THIS STUDY. (SOURCES: ALBERS, 1990;CLINICALRESEARCHASSOCIATES, 1991;JOHNSON et al., 1991) AdhesiveSystem
Component
Chemical Composition
Batch Number
All-Bond
Conditioner Primer A Primer B D/E BondingResin
SA-HEMA NTG-GMA BPDM Bis-GMA,UDMA, HEMA
029151 069101 069241 069271
Activator AdhesiveAgent Base Catalyst
citric acid, ferric chloride HEMA 4-META, MMA, HEMA tri-butyl borane
10101 030891-364494 10101 10102
Kuraray/J. Morita Tustin,CA, USA
K-Etchant Universal Catalyst
40% phosphoricacid Bis-GMA, HEMA, 10-MDP aromatic compounds
611116 057 611116229 611116 127
Gluma
D/E Conditioner
oxalic acid, AI nitrate, glycine HEMA, glutaraldehyde Bis-GMA
D666/2WJK8500 029187 RZl12 029209 RZ113
Bisco Itasca, IL, USA Amalgambond
Parkell Farmingdale,NY, USA CleaffilPhoto B o n d
Bayer/MilesDental South Bend, IN, USA Prisma UniversalBond3
CaulldDentsply Milford, DE, USA PowerBond
Cosmedent Chicago, IL, USA Scotchbond2
3M Dental Products St. Paul, MN, USA Tenure
Den-Mat Santa Maria, CA, USA XR-BondingSystem
Kerr Romulus,MI, USA
Primer Sealer Primer Adhesive
HEMA, PENTA HEMA, PENTA, urethaneresins
100190
Conditioner Primer A Primer B D/E Adhesive
SA-HEMA NTG-GMA CPDM, TCDM Bis-GMA, UDMA, HEMA
039201 039191 039121 039251
Scotchprep Adhesive
HEMA, maleicacid Bis-GMA, HEMA
P910215 P910215
Conditioner SolutionA SolutionB Visar-Seal
AI oxalate, nitricacid NTG-GMA PMDM Bis-GMA
291050 461040 462060 199026
XR-Primer XR-Bond
phosphateester phosphateester, UDMA
053.47 50.35
121190
Bis-GMA:bisphenolglycidylmethacrylate,BPDM:biphenyldimethacrylate,CPDM:cyclopentaldimethacrylate, HEMA:2-hydroxyethylmethacrylate,NTG-GMA:N-tolylglycine-glycidylmethacrylate,PENTA:phosphonated penta-acrylateester, PMDM:pyromelliticacid diethylmethacrylate,SA-HEMA:succinicacid + hydroxyethyl methacrylate,TCDM:tricyclicdimethacrylate,UDMA:urethanedimethacrylate,4-META:4-methacryloxyethyl trimelliticacid, 10-MDP: 10-methacryloyloxydecyldihydrogenphosphate.
by a strip chart and converted to MPa units using the crosssectional area of the composite posts. Data were analyzed with a one-way analysis of variance (ANOVA) and post hoc Duncan's multiple range test for pairwise contrasts using the SAS statistical software package (SAS Institute, Cary, NC, USA). The significance level was set at p
