Effect of used diamond burs on dentin bond strength

Many researchers have reported that, constant use of diamond burs can reduce their cutting efficacy during cavity preparation. The aim of this study was to evaluate the effect of changes in diamond bur sharpness on dentin bond strength when using self-etch bonding system. A total of seventy-two caries-free human 3rd molars were included in this in-vitro investigation. The teeth were sectioned in occlusal surface in order to expose dentin, and then were randomly divided into four groups. For dentin preparation, a fine diamond bur was used in group 1, a new coarse diamond bur was used in group 2, a used coarse diamond bur was used in group 3 after applying on porcelain for two minutes, and a used coarse diamond bur was used in group 4 after it was applied on porcelain for ten minutes. Unique composite capsules were bonded to all dentin surfaces using Clearfil SE Bond and then cured. After storage for 24 hours in 37○C distilled water, the bonded teeth were subjected to shear testing by using Instron testing machine. The bond strengths were calculated and recorded as failure. Bond strength data were analyzed by One-Way ANOVA and Tukey tests. The mean (Standard Deviation) of shear bond strength in each group can be reported as follows: 22.2Mpa(3.38) for group one, 18.05Mpa(4.54) for group two, 24.5Mpa(5.69) for group three and the figure was 22.4Mpa(4.52) for group four. The statistical analysis demonstrated that Shear bond strength of new coarse diamond bur preparations were significantly (P<0.001) less than fine or used diamond burs. Used diamond burs of different durations can affect dentin bond strength of SE Bond self etch bonding system. Accurate type of bur and adhesive selection are essential in optimizing dentin adhesion to self-etching adhesives.