Influence of changes to application protocol in shear bond strength of a one-step self-etch adhesive

Objectives: To evaluate the influence of changes on the application protocol of an one-step self-etch adhesive on the shear bond strength and the bond failure type to human dentin. Materials and methods: 80 slices of dentin were obtained from 40 non-carious human molars and randomly distributed by experimental groups (n = 20) according to the application protocol of Adper (TM) Prompt (TM) L-Pop (TM): 1) manufacturer's instructions, 2) pre-etching, 3) additional adhesive layer, 4) additional hydrophobic layer. Composite was applied over light cured adhesive system and specimens were stored for 72 hours (37 degrees C -100% relative humidity). Shear bond strength tests were performed and the type of failure was evaluated. The bond strength values were analyzed using ANOVA followed by Tukey's post-hoc tests, and the type of failure with non-parametric statistical tests (Kruskal-Wallis and Mann-Whitney). Results: The mean bond strength values ranged from 7.56MPa to 19.31MPa. The application of additional adhesive layer and additional hydrophobic layer yielded statistically higher bond strength values than the application according to the manufacturer's instructions or with pre-etching (p < 0.05). The failure type obtained was predominantly adhesive in all experimental groups, with the exception of the hydrophobic layer group, where the failure was mostly mixed. Conclusion: It is possible to increase the bonding values of the adhesive studied by changing manufacturer's instructions. (C) 2011 Sociedade Portuguesa de Estomatologia e Medicina Dentaria. Published by Elsevier Espana, S.L. All rights reserved.