Objective: To investigate if micro-tensile bond strength (µTBS) of composite-resin to dentin was affected by contamination with HF.
Methods: Fifteen lower third molars were mounted in blocks and the occlusal third of the crown was removed. On each tooth a standard smear layer was produced using a 100µm grit diamond bur. Exposed dentin was subjected to one of five different etching procedures (n=3): Group A (Control): 37% H3PO4 (DMG); B) 37% H3PO4 followed by 3% HF (DenMat); C) 37% H3PO4 followed by 9.6% HF (Ultradent); D) 3% HF followed by 37% H3PO4; E) 9.6% HF followed by 37% H3PO4. After etching, OptiBond FL (Kerr) was applied and a composite-resin build-up was made (Clearfil AP-X). After 1 week water-storage, out of each block 4 specimens of 1.8x1.8x8mm were prepared with a constriction at the interface (surface area about 1 mm2). Beams were stressed in tensile to determine the µTBS. ANOVA and Tukey multiple comparisons were used to determine significant differences (p<0.05). SEM was done on representative samples for detailed failure analysis.
Conclusions: Due to the adverse effect on µTBS of composite to dentin, it seems that contamination of HF should be avoided when repairing a defective restoration.