Adhesive application before hydrofluoric acid etching during repair procedure in dentistry?

To evaluate the influence of hydrofluoric acid (HF) contamination on the microtensile bond strength (μTBS) during dental repair procedures before and after application of different dentin adhesives (Optibond FL and Optibond XTR). Thirty-five human molars were ground down into the dentin and were randomly divided into seven groups (G1-G7; n = 5), G1 and G2 being the control groups. Only in the test groups (G3-G7) samples were subjected to HF (9,5%) contamination. Two adhesive systems, Optibond FL (G1, G3, G4, G6) and Optibond XTR (G2, G5, G7) were used. In G3-G5 the adhesive was applied before and after contamination, the test groups G6 and G7 were treated with a single adhesive application after contamination. After composite build-up, samples were stored in water (7 d) and μTBS was determined. Data were evaluated using Wilcoxon test (p