Estabilidade físico-química de resinas compostas dentais

Abstract

Resin composites are direct restorative materials that possess satisfactory clinical and esthetic performance, although they are susceptible to degradation processes when exposed to the oral environment. The purpose of this study was to investigate the degradation behavior of two nanofilled resin composites, one nano-hybrid and one micro-hybrid, which were subjected to in vitro pH cycling simulating cariogenic challenge, in comparison to a solution with neutral pH (artificial saliva). Twenty samples of each resin composite (Vittra, Forma, Filtek Z350 and Filtek Z250) were prepared, which were subsequently submitted to thermogravimetric analysis, sorption and solubility testing in different immersion media, and to superficial wettability analysis. The data were analyzed using ANOVA and the post hoc Tukey test, as well as Pearson correlation test to investigate the association between wettability and sorption/solubility (α=5%). The resin composites showed similar hidrophilicity when immersed in artificial saliva (p≥0.156). Concerning pH cycling, Vittra exhibited greater hydrophilicity gain when compared to the other materials (p≤0.017). With regard to the sorption of samples immersed in artificial saliva, Vittra, Forma and Filtek Z350 demonstrated the greatest values, which were similar to each other (p≥0.064). Conversely, Vittra showed the greatest sorption when considering the pH cycling protocol, followed by Filtek Z350, Forma and Filtek Z250. Vittra displayed the greatest solubility in the study, regardless of the immersion medium (p<0.001). The hydrophilicity gain (wettability) of the resin composites showed a positive and Strong correlation to the sorption property (R 2 = 0.8553; p<0.001) and a weaker relationship to solubility (R 2 = 0.5456; p=0.03). In conclusion, the average size and type of inorganic fillers seem to have a determinant effect on the physico- chemical stability of resin composites.