Influência da clorexidina na resistência de união à dentina, morfologia de interface adesiva e nanoinfiltração de cimentos resinosos

This study focused on adhesive interface morphologic characterization, nanoleakage expression and microtensile bond strength of two resin cements (RelyX ARC and RelyX U100) bonded to human dentin treated with Chlorhexidine. Forty non-carious third molars were ground flat to expose superficial dentine. Composite blocks were luted to the exposed dentine with/without chlorhexidine pre-treatment. Four experimental groups (n=10) were obtained: ARC, U100, ARC/CHX and U100/CHX. Control groups, ARC and U100, were not treated with chlorhexidine. Experimental groups, ARC/CHX and U100/CHX, were pre-treated with chlorhexidine prior to the luting process. After storage in water for 24h, the bonded teeth were sectioned into 0.9 x 0.9 mm cross sectional area sticks. Eight random sticks from each tooth were submitted to microtensile bond test at a crosshead speed of 0.05 mm/min until failure. Two sticks were prepared for hybrid layer evaluation by SEM analysis. Two sticks were immersed in silver nitrate for 24h for nanoleakage evaluation. Nanoleakage samples were carbon coated and examined using backscattered electron mode. Bond strength data were analyzed with analysis of variance (ANOVA) followed by Tukey Test (p<0,05): ARC (42.72 ±4.3)A, ARC/CHX (39.19 ±9.62)A, U100 (12.98 ±3.43)B, U100/CHX (11.97 ±2.6)B. An increase in nanoleakage was observed in groups treated with chlorhexidine for both resin cements. No well- established hybrid layer was identified in the U100 groups. Even though the use of chlorhexidine did not interfere on the bond strength values within each cement, its use along with self-adhesive cements adversely affects the resin-dentin bond morphology which in turn might compromise the resin-dentin bond stability over time.Mestre em OdontologiaEsse estudo avaliou a morfologia da interface adesiva, nanoinfiltração e resistência de união dentinária de dois cimentos resinosos, RelyX ARC e RelyX U100 unidos à dentina pré-tratada e não tratada com digluconato de clorexidina 2%. As superfícies oclusais de quarenta terceiros molares hígidos foram planificadas com lixas de carbureto de silício e blocos de resina composta foram cimentados na dentina exposta tratada ou não tratada com clorexidina. Quatro grupos experimentais foram obtidos (n=10): ARC, U100, ARC/CHX e U100/CHX. Os grupos controle, ARC e U100, não foram tratados com clorexidina. Os grupos experimentais foram tratados com clorexidina previamente à cimentação. Após o armazenamento em água destilada por 24h, foram seccionados palitos de dimensão 0,9 x 0,9 mm de secção transversal. Oito palitos selecionados aleatoriamente foram submetidos ao ensaio de microtração a 0,5 mm/min até sua ruptura. Dois palitos foram preparados para avaliação morfológica da interface adesiva por Microscopia Eletrônica de Varredura (MEV). Os dois palitos restantes foram infiltrados com nitrato de prata amoniacal para análise da nanoinfiltração na interface adesiva. Os espécimes para nanoinfiltração foram cobertos com carbono e examinados em modo elétron retroespalhado. Os resultados do teste de microtração foram analisados com ANOVA seguido do Teste de Tukey (p