Double application of cement's primer improved cement-dentin bond strength

Objectives: The aim of this study was to evaluate the effects of the double application of resin cement’s primers to dentin prepared with different diamond burs on the cement-dentin microtensile bond strength.
Methods: Human third molars were cut to expose mid-coronal dentin 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’s primer application: single application (SA) or double application (DA); and (3) dentin surface preparation with regular (R) or superfine (SF) diamond bur. Cement-dentin sticks (1 mm²) were prepared for microtensile bond strength test (µTBS) according to non-trimming technique. Data were analyzed by three-way ANOVA and Duncan test (α = 0.05). Fractured surfaces and cement-dentin interfaces were observed by scanning electron microscopy (SEM). Additional teeth were prepared to observe the demineralization effect of resin cement’s primer with SEM and TEM.
Results: All tested factors demonstrated significant effect on µTBS (p < 0.001). ML showed the lowest µTBS with the highest number of pre-testing failure. SF prepared surfaces demonstrated higher µTBS than R, but a significant effect was observed in ML with DA and PV with SA. DA significantly increased bond strength for most combinations, except for PV with SF prepared dentin.
Conclusions: PV showed higher bond strength than the others. DA improved dentin bond strength of all cement. Cement-dentin bond strengths were higher when dentin was prepared with SF burs.