Application of a New Microtensile Bond Strength Testing Technique for the Evaluation of Enamel Bonding

Objective: To evaluate adhesives' enamel bonding performance utilising the traditional microtensile bond strength test (mu TBST) and a new double-sided microtensile bond strength test (D mu TBST) to assess the suitability of the latter. Methods: A 'tug-of-war' direct encounter design was employed to compare the enamel bond strengths of two universal adhesives and their different application modes simultaneously under the same tensile load applied to double-sided bonded specimens. Clearfil Universal Bond (CU; Kuraray, Kurashiki, Japan) and Scotchbond Universal Adhesive (SB; 3M ESPE, St Paul, MN, USA) were applied in self-etch (S) and etch-and-rinse (E) mode on 110 human molar samples to perform two experiments. Experiment 1 compared the enamel bond strengths of the combinations of adhesive application modes utilising mu TBST. The data were analysed using a Welch analysis of variance (ANOVA), followed by a Games-Howell test. Experiment 2 employed D mu TBST to determine the suitability of the new double-sided bonded assembly and ascertain which of the adhesive application mode combinations was superior. The data were analysed using a Kaplan-Meier survival analysis, followed by pairwise comparisons with a Mantel-Cox log-rank test. The level of significance was set at P < 0.05. Results: The mu TBST results did not show significant differences for CUE vs CUS, SBE vs SBS, CUS vs SBS and CUS vs SBE (P < 0.05); however, from D mu TBST, the survival distributions for the interventions were statistically significantly different (chi(2)(3) = 145.130, P < 0.0005), indicating the superiority of universal adhesive CU over SB and application mode E over S with certainty. Conclusion: D mu TBST was able to add more discerning outcomes to the mu TBST results, indicating that the new technique could become a valuable adjunct to the conventional method.