Influence of crosshead speed on resin-dentin microtensile bond strength

Purpose: The aim of this study was to investigate the influence of testing speed on the microtensile bond strength values of two adhesive systems to dentin. Materials and Methods: A flat dentin surface was exposed after grinding the occlusal enamel of 10 human third molars. The adhesive systems (n = 5 each) Single Bond and Clearfil SE Bond were applied according to the manufacturers' instructions, and composite resin crowns (Z250) were constructed incrementally. After 24 h in distilled water at 37degreesC, each tooth was longitudinally sectioned in both the x and y directions, under a cutting speed of 300 rpm, to obtain sticks with a cross-sectional area of 0.8 mm(2). The sticks from each tooth were divided into 5 groups to be tested under crosshead speeds of 0.1, 0.5, 1.0, 2.0, and 4.0 mm/min. The fracture pattern was analyzed microscopically after debonding (400X). A two-way ANOVA having adhesive system (2 levels) and testing speed (5 levels) as main factors was used to compare the microtensile bond strengths. Results: The two-way ANOVA did not detect statistically significant differences either for the interaction (p = 0,80) or for the crosshead speed (p = 0.69). Differences were only detected between adhesive systems (p = 0.001), with Single Bond showing higher bond strength values than Clearfil SE Bond. Conclusion: The crosshead speed used for microtensile bond strength tests does not influence the bond strength values, regardless of the adhesive system employed.