Thermocycled Shear Bond Strength of Three Self-etching Bonding Agents

Self-etching bonding agents bond well initially but long term bond has yet to be determined.  Objective: This study measured the shear bond strength to enamel of 3 self-etching bonding agents to enamel 24 hours after bonding and after 20,000 thermocycles. Methods: 60 recently extracted teeth were ground with abrasive discs ending at 320 grit to form a uniform enamel bonding area.  Prompt L-Pop, Clearfil SE Bond and Gluma AC Bond were applied to 20 teeth according to manufacturers’ directions. After curing the bonding agent, a tube of Z-250 (Shade A2) composite resin was applied, cured for 40 seconds and the tube removed.  After storing the specimens in deionized water for 24 hours, half were debonded in shear in an Instron at a 5mm/minute crosshead speed.  The other half was thermocycled for 20,000 cycles between 6 and 60⁰C.  These were debonded using the same method.  Failure loads were converted to shear bond strength by dividing by the area. Groups were examined for intergroup differences using 2 factor ANOVA and Tukey HSD multiple comparisons procedure post-hoc analysis.  Mean shear bond strengths are shown in MPa. (n= 10).   Results: Material                        Thermocycled               Shear Bond Strength  Standard deviation

Before thermocycling 3 different groups were present, after thermocycling 2 groups were present with Gluma AC Bond being significantly weaker that the others.  Conclusion: Some self-etching materials may provide long-term durable bonds to enamel.