Effects of diamond bur particle size on dentin bond strength

To evaluate the influence of particle size of originally designed diamond burs on resin adhesion to sound young human permanent dentin.

The buccal surfaces of 105 premolars were used. Six test groups were prepared. The adhesive systems and resin-based composites used for Groups 1-3 were Clearfil SE Bond (SE) and Clearfil AP-X, and for Groups 4-6, Single Bond (SB) and Z250. Flat dentin surfaces were finely ground with 25 microm particle size IW-G5 diamond bur (IW-G5, Groups 1 and 4), 50 microm particle size IW-G4 diamond bur (IW-G4, Groups 2 and 5), or 600-grit SiC paper (#600, Groups 3 and 6). The microstructure of the prepared dentin, SE primed or SB etched dentin, and resin-dentin interfaces of each group (3 teeth/group) were studied using SEM. Shear bond strengths (SBS) in MPa were tested (10 teeth/group), and the failed surfaces were observed using SEM. Data was statistically analyzed using ANOVA and Fisher's PLSD at P < 0.05.

The dentin ground with the IW-G5 or IW-G4 bur was rougher than the dentin ground with the 600-grit SiC paper. The mean SBS (MPa) for Groups 1-6 were: 32.3 +/- 5.0, 27.6 +/- 6.4, 21.3 +/- 3.6, 5.9 +/- 2.9, 6.5 +/- 3.1 and 5.3 +/- 2.0. The SBS of Groups 1-3 (SE groups) were significantly higher than those of Groups 4-6 (SB groups). The SBS of Group 1 (IW-G5, SE group) was significantly higher than those of Groups 2 (IW-G4, SE group) and 3 (#600, SE group), and the SBS of Group 2 was significantly higher than that of Group 3. There was no significant difference for SBS among Groups 4, 5 and 6. Fracture mode after SBS test mainly showed mixed fracture (adhesive and cohesive resin fracture) for the SE groups, and adhesive fracture for the SB groups.