Dentine drying influence on the bond strength in MOD preparations

Objectives: the objective of this study was to evaluate the influence of 4 different methods to remove the excess of water, after dentin conditioning, on the microtensile bond strength (BS) in function of the different regions in MOD preparations. Methods: MOD cavities were prepared in 40 sound human molars (6mm wide X 2mm depth, and cervical walls 1mm bellow CEJ). Teeth were randomly assigned into 4 groups, according to the 4 drying methods: air-spray (AS); absorbent paper (AP), cotton pellet (CP), and brush (B), restored with the adhesive system One Step and TPH Spectrum composite and stored in distilled water for 24h. Teeth were then sectioned in perpendicular directions to obtain sticks (0.8mm²) from cervical, axial and pulpal walls. Sticks were tested under µ-tensile mode (0.5 mm/min). Data was submitted to two-way ANOVA (drying method and cavity wall) and Tukey post-hoc test (same letters indicate statistical similarity). Results: BS values (mean±SD) of the different drying methods were significant (p=0.012): AS: 26.83±12.49a; AP:34.97±10.93ab; CP:38.99±16.65ab; B:44.75±19.03b. Although the effect “cavity wall” was not significant (p=0.27), the interaction was (p=0.036). Only the group AS showed different BS values in function of the cavity wall (pulpal: 37.16±11.17a; cervical: 20.38±4.68ab; axial: 16.04±2.30b). Conclusion: The application of air spray in view to remove excess of water in dentin should be avoided due to the consequent decrease in BS, and the resultant BS variation in the different cavity walls under this condition.