Method to compare μ-tensile bond strength of a self-etching adhesive and μ-cohesive strength of adjacent dentin

Laboratory results from tensile or micro-tensile testing of adhesive/restorative systems need a gold standard to make their interpretation possible. This can be done by comparing the μ-tensile bond strength (μTBS) of the tested adhesive(s) with the μ-tensile cohesive strength (μTCS) of the adjacent dentin, which is meant to be replaced by the restoration. Objectives To test immediate μTBS of an adhesive/restorative system versus μTCS of the dentin adjacent to the bonded interface, in perfused specimens. Methods Enamel and roots of five-third sound molars were removed and teeth were perfused (30 cm distilled H2O) until after the bonding procedure was completed. Parallel grooves (1.5-mm wide×1.5-mm deep, separated by 1.5 mm), were drilled in the exposed dentin, under water refrigeration. Teeth were restored (AdheSE/Filtek Z250). Specimens were sawn from grooves to test μTBS (n=30) and from between grooves to test μTCS (n=32) of dentin, adjacent to adhesive interfaces, both areas to be tested at the same relative depth. Areas to be studied were rounded (mean bonded surface area for both groups, BA=0.68 mm2), and μTBS and μTCS were found. As not all BAs were identical, residuals of μTBS and μTCS values to the regression line relating BA and tensile test results (representing the null hypothesis, i.e. μTBS=μTCS) were compared using a non-parametric test. Results Difference in the means of residuals was not statistically significant (two tails p=0.067). Significance mean μTBS of the tested adhesive was not different to mean μTCS of adjacent dentine. The null hypothesis was not rejected.