Influence of Crosshead Speed on Resin-Dentin Microtensile Bond Strength

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. 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 37°C, 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 mm2. 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. 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. The crosshead speed used for microtensile bond strength tests does not influence the bond strength values, regardless of the adhesive system employed. Keywords: microtensile test, crosshead speed, resin-dentin bond strength