Microtensile bond strength of current adhesive systems when compared to cohesive strength of sound dentin and a resin-based composite

purpose: to evaluate the microtensile bond strength (μtbs) to dentin of 4 adhesive systems, the micromorphology of the adhesive/dentin interface and to compare the results to the μts (cohesive strength) of sound dentin and resin composite. occlusal surfaces of 24 extracted caries-free human molars were cut flat to expose the dentin surface. they were randomly assigned to 4 groups (n = 6): adper scotchbond multi purpose plus (mp), adper single bond (sb), clearfil protect bond (cp) and adper prompt (ap). adhesive systems were applied and "crowns" were built using z100. other 5 human molars were sectioned to obtain square-shaped dentin blocks and 5 resin blocks were built using a composite resin, z100. after storage in distilled water at 37 °c for 24 h, stick-shaped specimens were obtained for all groups (n = 5) with 0.8 mm2 and subjected to μtbs or μts test. results were analyzed using one-way anova and tukey's test at p < 0.05. the remaining bonded teeth were cut in two halves perpendicularly to the bonded interface and prepared for sem analyses. no significant differences were found among cp (45.6 + 7.4 mpa), sb (43.3 + 6.5 mpa) and mp (35.1 + 5.9 mpa) (p > 0.05). the lowest result was found for ap (27.4 + 4.7 mpa), although not statistically different from mp. most specimens (89.4%) showed predominant adhesive failure. none of the systems tested reached the μts values of dentin (108.5 + 9.4 mpa) and z100 (86.5 + 3.6 mpa). bonded interfaces showed lower μtbs than those μts of dentin and resin composite blocks. the all-in-one self-etching adhesive had the lowest μtbs.