Condicionamento com ácido fosfórico \"tradicional\" vs. autolimitante, por diferentes tempos, na resistência de união de um cimento resinoso fotopolimerizável convencional e de um dual autoadesivo ao esmalte bovino

Abstract

Silva JCV. "Traditional" vs. self-limiting phosphoric acid etching for different times on the bond strength of a conventional light-curing resin cement and a self-adhesive dual curing resin cement to bovine enamel [dissertation]. São Paulo: Universidade de São Paulo, Faculdade de Odontologia; 2019. Versão Original.The success of ceramic veneers and pieces depends on a good interaction between the dental substrate and the resin cementing system and its interaction with the restoration, since that, beyond the small dimensions involved, it is not determined, as a rule, any other form of retention of the piece. For this reason, it is important the proper acid etching of the enamel, non or minimally prepared, determining the adhesive interface most susceptible to debonding. Thus, bond strength (BS) of a conventional vs. self-adhesive resin cement to the bovine enamel was evaluated in relation to acid etching (phosphoric) with different attributes and for diverse times of application. Bovine enamel fragments, included in acrylic resin (0.5" PVC cylinders), were planned and subjected to standard smear layer creation (SiC #180 and #600/1 min sandpaper). They were then etched with different acids (EU: Ultraetch ® / CDG: Dental Gel ® Conditioner), for different times (0s -control / c; 15s; 30s; 60s; 120s), and to the construction of microcylinders (7 per tooth; 1 mm in diameter) with one of the resin cements: RV / RelyX Veener ® (previous application of Scotchbond Multipurpose adhesive) or R200 / RelyX U200 ® . After 24h, they were submitted to a microshear test (1 mm/min), evaluating the type of failure with a digital microscope (40X). Regarding as experimental factors the type of cement (in two levels), the acid agent for enamel etching (in two levels) and its the time of action (in four levels), a statistical analysis of the data obtained was performed by means of a 3-way ANOVA analysis and a Tukey test. To compare each of the experimental groups individually and with control groups, Kruskal-Wallis and Tukey tests were used once the distribution was normal (Shapiro-Wilk, p = 0.137) but not homogenous (Equal Variance Test, p < 0.05). In all cases a significance level of 5% was adopted.Regardless of the cement used and its time of application, etching with traditional acid always revealed greater BS values than those with self-limiting acid.Additionally, regardless of the applied acid and of the time of its action, use of the dual self-adhesive always obtained higher values of BS than the light-curing conventional one. Regarding the cement or the acid used, the time of application of the light-curing conventional cement did not exert any significant influence over the results. Comparatively to the non-etching, the one with any of the acids and any of the application time always favored BS of both cements to enamel. At the moment, within the indications of each of the cements and having in mind that the selfadhesive cement can be related to a better adhesion to enamel, as long as associated to previous acid-etching, it see...