Different Concentrations of Ethanol as Dentin Pre-treatment to Bonding of an Etch-and-rinse Adhesive

Objective: to evaluate the bond strength (BS) to dentin pre-treated with ethanol in single application for 20 s after etching and before application of a two-step etch-and-rinse adhesive and to analyze the morphological features at the resin-dentin interface. Methods: twenty four third molars were collected and randomly assigned into four groups (n=5) according to the ethanol concentration: control (traditional water-wet technique), 50vol%, 70vol% and 100vol%. In experimental groups, ethanol was applied for 20 s and gently air-dried for 5 s. Bonding procedures were performed and resin composite was built up incrementally. Bonded teeth were sectioned into 0.8mm2 sticks on average. These specimens were submitted to microtensile bond strength test (μTBS). One-way ANOVA and post hoc Tukey's test were applied to analyze statistical data (α=0 05). Light microscopy (LM) assisted by Masson's trichrome staining was used to observe the features of resin/dentin interfaces. Results: control BS was not different from ethanol 50vol% (p>0.05). However, the pre-treatment using ethanol 70vol% and 100vol% showed increase on BS (p<0.001 and p=0.003 respectively) with no difference between these two groups. LM Showed a discrete decrease in denuded collagen fibrils to teeth treated with 70vol% and 100vol%. Conclusion: the pre-treatment of dentin using ethanol may increase the initial BS of resin/dentin interface when applied using 70vol% or 100vol% ethanol. Ethanol 70vol% is also able to decrease the thickness of the resin-sparse collagen fibrils.