Influência de iniciadores no foto-envelhecimento e na resistência de união de cimentos resinosos experimentais

Abstract

With the ample craving for teeth whitening, it is fundamental the production of increasingly clearer materials and also a good color stability, before the possible degradation which are exposed. The camphorquinone (CQ) is the photo initiator most widely applied on the dental composite, but it has the yellow coloration and suffers darkening when exposed to ultraviolet light (UV), endangering the maintenance of the esthetics harmony. The goal of this study was to evaluate in vitro the effect of the photo initiator Phenylpropanodione, singly or in association with the CQ, about the color stability of the resinous photoactive cement and its bond adhesive resistence, by microshear. The null hypotheses are: i) the photo initiator PPD does not interfere with the color changing of the resin cement, after the photoaging motivated by prolonged exposure to UV light; and ii) the photo initiator PPD does not interfere with the resistance of the adhesive bond of resin cement to the ceramic. Four resinous cements where used, which one of them was commercial (RelyX Venner, 3M/ESPE) and three experimental, differing each other's photo initiator's concentration. For the color analysis, ceramic discs were cemented above the bovine dentine, simulating the indirect restorations (n=8), being exposed to 120 h of UV, and tested about the color alterations which were measured applying the CIELab scale, by spectrophotometer of reflectance. The obtained datas were verified about the normal distribution, for then being submited to ANOVA and to the complementary test Tukey, all with 5% significance. The results of color analysis do not statistically significant difference to E of 4 cements studied neither to L , a and b . For the Union of Resistance of all cements studied showed statistically significant differences among themselves, with the highest for commercial cement RelyX Venner® (29.07 MPa), followed by cement with CQ (21.74 MPa) , and cement CQ + PPD (19.09 MPa); and the lowest result was obtained with the cement using only the PPD as photoinitiator (13.99 MPa) . Therefore to the parameters studied in this work, the PDD was not advantageous as photoinitiator resin cements, because made low bond strength value ceramics and not demonstrated superiority as for color stability .