Adhesion testing with the microtensile method: effects of dental substrate and adhesive system on bond strength measurements

Purpose: To evaluate the bond strength of a self-etching primer (SE, Clearfil SE Bond) and a one-bottle adhesive system (EX, Excite) on enamel and dentin. Materials and Methods: Twenty-eight sound human molars were used. The teeth were randomly divided into four groups (n = 7): SE applied to enamel (SE-E); SE applied to dentin (SE-D); EX applied to enamel (EX-E); EX applied to dentin (EX-D). A resin (Tetric Ceram) block of approximately 5 × 5 × 5 mm was built up on the tooth and cured for 40 s. After 24 h, samples were obtained by cutting along the x and y axis of the tooth. Stick-shaped samples of approximately 0.8 mm2 cross-sectional area were obtained. The sticks underwent microtensile testing. Results: The tensile bond strength (MPa) values of the test groups were: SE-E, 38.9 (± 4.8); SE-D, 44.5 (± 7.7); EX-E, 45.8 (± 4.7); EX-D, 42.9 (± 7.1). These values were not statistically significantly different. Conclusion: The null hypothesis was accepted that there is no difference between the self-etching primer and the one-bottle adhesive tested here. In addition, the bonding conditions provided by either bonding material on enamel were not significantly more favorable than on dentin. The majority of the specimens failed adhesively under load.