Fatigue Limits of Enamel Bonds Using Single and Multi-step Adhesives

Fatigue testing of adhesive bonds to tooth structures may be an effective way to predict the clinical survival of dental adhesives. Objective: The purpose of this study was to determine the shear fatigue limit (SFL) of composite to enamel bonds comparing a three-step etch and rinse adhesive with a two-step and one-step self etching adhesive system. Methods: Ten specimens each were used to determine 24-hour composite (Z100 – 3M ESPE) to enamel shear bond strengths (SBS). All Bond 3 (AB3), and All Bond SE used with a resin liner (ABSE-R) and without a resin liner (ABSE) were tested.  A staircase method of fatigue testing was used employing an MTS MiniBionix Servohydraulic systen to determine the SFL of composite to enamel bonds with the adhesives (20 specimens for each adhesive) at 5 Hz for 40,000 cycles. ANOVA and Tukey's post hoc test were used for the SBS data and a modified t-test with Bonferroni correction was used for comparisons of the SFL. Results:

There was a significant difference (p<0.001) in the SBS and SFL among the systems tested.  The  etch and rinse system generated the highest SBS and SFL followed by ABSE with the liner with ABSE alone being lowest. The ratio of SFL/SBS was less for the self-etch systems when compared to the etch-and-rinse system. Conclusions: The etch-and-rinse adhesive system produced significantly higher composite to enamel shear bond strength and fatigue limit than the self-etch systems. The use of the liner with the self-etching system improved both SBS and SFL.