Influence of crosshead speed on micro-tensile bond strength of two-step adhesive systems

Objectives The purpose of this study was to determine the influence of crosshead speed on the micro-tensile bond strength of two separate adhesive systems to dentin. Methods The systems used were the Clearfil SE Bond (Kuraray Medical) and the Single Bond (3M ESPE) combined with a resin composite Clearfil AP-X (Kuraray Medical). Dentin surfaces of bovine madibular incisors were primed with self-etching primer followed by air blowing for Clearfil SE Bond, or etched with phosphoric acid followed by rinsing with distilled water for Single Bond, and adhesive was applied. The resin composite was then built up in three layers and light activated. After 24 h storage in water, specimens were sectioned and trimmed to a cross-sectional area of 1 mm2 and subjected to a micro-tensile bond-strength test. Ten samples per test group were tested at crosshead speeds of 0.5, 1.0, 5.0 and 10.0 mm/min. Micro-tensile bond-strength values (in MPa) were calculated from the peak load at failure divided by the specimen surface area. Two-way ANOVA was performed at the 0.05 probability level. Results The mean dentin bond strength at different crosshead speeds ranged from 34.6 to 37.1 MPa for Clearfil SE Bond and from 44.3 to 50.4 MPa for Single Bond. There was no significant difference among the same adhesive systems with the different crosshead speeds tested. Significance The influence of the crosshead speed might be negligible when measuring micro-tensile bond strengths.