Effects of dentifrices on mechanical resistance of dentin and restorative materials after erosion and abrasion

The aim of this study was to evaluate the mechanical resistance of dentin and restorative materials submitted to erosive/abrasive challenges with different dentifrices. The dentin was restored using a resin-modified glass-ionomer (RMGIC) or a composite resin (RC). One hemiface of the sample was protected, and the other was subdivided according to the applied dentifrice (n = 10): without fluoride (SF), sodium fluoride (NaF) and stannous fluoride (SnF). The specimens were submitted to erosive/abrasive cycles, the varnish was removed, and the Martens hardness (HMV) and elastic modulus (Eit) were evaluated. The data were analyzed by repeated two-way ANOVA measurements and Tukey tests (alpha = 0.05). When analyzing the HMV on the test side, there was no influence of the dentifrices in the dentin; however, the orders of NaF < SnF = SF in RC and SnF > NaF = SF in RMGIC were observed. Comparing the treated surfaces, there were no differences in the dentin, and only the SF since CR presented an HMV superior to that of RMGIC. Comparing control and test sides, both dentins obtained a decreased HMV after the erosive/abrasive challenge; for the restorative materials, superior values were found only for SnF in the RMGIC. The Eit values were influenced more by the dentifrices on the test side for the dentin adjacent to the RMGIC, with the lowest values shown for the SF, and for both materials, the highest values were shown for the SnF group. No differences were found when comparing each dentin treated with the same dentifrice; however, the RMGIC presented a superior Eit than the CR when brushed with both dentifrices with a fluoride. Comparing the control and test sides, the same results were obtained for the HMV. The dentifrices showed little influence on the dentin substrate, whereas the dentifrice with SnF enhanced the mechanical properties of the restorative materials, which was more evident in the RMGIC.