Effect of Diamond-Coated Ultrasonic Tip Finishing on Resin Cement Bond Strength to Dentin.

This study aimed to evaluate the effect of dentin surface finishing protocols using ultrasonic CVD diamond tips on the bond strength of resin cement to dentin. Seventy-two bovine incisor crowns were prepared and assigned to four dentin surface finishing protocols (Groups 1-4, n = 18), including a conventional control group and experimental groups using ultrasonic CVD diamond tips applied sequentially with increasing fineness. One specimen per group was analyzed by scanning electron microscopy to assess surface topography and smear layer characteristics. The samples were bonded using light-cured resin cement in combination with three adhesive strategies: total-etch, self-etch, and universal adhesives. After 24 hours of storage in distilled water, microshear bond strength testing was performed (0.5 mm/min). Data were analyzed using two-way ANOVA and Tukey's post hoc test (α = 0.05). Groups 3 and 4 showed significantly higher bond strength than the control group (p < 0.05), while no significant differences were observed among adhesive strategies (p > 0.05). Surface analysis revealed that these protocols produced a more homogeneous and regular smear layer, whereas intermediate finishing resulted in a more irregular surface. It can be concluded that the sequential use of ultrasonic CVD diamond tips with increasing fineness improves the bond strength of resin cement to dentin and promotes a more favorable substrate for adhesion.