Effects of Double Application of a Resin Cement Primer and Different Diamond Burs on Cement-Dentin Bond Strength.

PURPOSE: To evaluate the effects of double application of resin cement primers to dentin prepared with different diamond burs on the cement-dentin bond strengths. MATERIALS AND METHODS: Sixty flat dentin surfaces were prepared and divided into 12 groups (n = 5) according to three experimental factors: 1. resin cements: RelyX Ultimate (RU), Multilink Automix (ML), and Panavia V5 (PV); 2. resin cement primer application: single or double; 3. dentin surface preparation with regular or superfine diamond burs. Cement-dentin sticks (1 mm2) were prepared for and underwent microtensile bond strength testing (microTBS). Statistical analysis was performed using three-way ANOVA and Duncan's test (alpha = 0.05). Fractured surfaces and cement-dentin interfaces were observed using SEM. Additional teeth were used to observe the demineralization effect of resin cement primers with SEM and transmission electron microscopy (TEM). RESULTS: All tested factors demonstrated significant effects on microTBS (p < 0.001). The combination of PV with superfine-grit bur and double application yielded the highest bond strengths. Surfaces prepared with superfine-grit burs demonstrated higher microTBS than did the regular-grit group, but a significant effect was not observed for all groups. The double application of primer significantly increased the bond strength for most combinations, except for PV with superfine-grit bur-prepared dentin. CONCLUSIONS: PV showed higher bond strengths than other resin cements. Double application of primer improved the bond strength of all cements to dentin. Bond strengths were higher when dentin was prepared with a superfine-grit bur.