Effects of different burs on dentin bond strengths of self-etching primer bonding systems

This study evaluated the effects of cutting dentin with different types of burs on tensile bond strength using three self-etching primer bonding syste ms (Clearfil Liner Bond 2 [LB2], Clearfil Liner Bond 2V [2V] and Clearfil S E BOND [SE], Kuraray, Co, Ltd, Osaka, Japan). Thirty-six intact extracted h uman third molars were ground flat to expose occlusal dentin, followed by p olishing the dentin surfaces with #600 SiC paper. The teeth were divided in to four groups according to bur type and grit: fine cut fissure Steel bur ( SB600), cross cut fissure steel bur (SB703), regular grit diamond bur (DB). Controls were abraded with #600 grit SiC paper (AP#600). The dentin surfac es of the SB600, SB703 and DB groups were cut under copious air-water spray with the respective burs mounted in a dental handpiece. The teeth were tre ated with one of three adhesive systems, then composite buildups were creat ed with Clearfil AP-X (Kuraray Co, Ltd, Osaka, Japan). After soaking in wat er at 37 degreesC for 24 hours, serial vertical sections (0.7 mm thick, 7-8 slices per one tooth) were made, trimmed to form an hour-glass shape with a 1.0 mm(2) cross-section and tensile bond strengths were determined at a c ross-head speed of 1 mm/min. Statistical analysis was made using one and tw o-way ANOVA and Fisher's PLSD test (p<0.05). Eight additional molars were p repared. Burs or abrasive paper were used for SEM observations of the denti n surfaces of each group before and after treatment with the self-etching p rimers. All adhesive systems yielded the same ranking of bond strengths to the surfaces prepared with different abrasives: from highest to lowest AP#6 00 > SB600 > SB703 > DB. This ranking reached statistical significance usin g Clearfil Liner Bond 2V (p<0.05). Therefore, when cutting dentin, selectin g the adequate bur type is important for improved bonding of adhesive syste ms using self-etching primer to dentin.