Microshear bond strength of composite resin to bovine enamel previously bleached with carbamide peroxide gel, in different concentrations.

O objetivo deste estudo in vitro foi avaliar a força de adesão de sistemas adesivos sobre superfícies de esmalte bovino submetidas previamente, ou não, a tratamento clareador com gel a base de peróxido de carbamida (Opalescence PF), em diferentes concentrações (10%, 15% e 20%), através de ensaio mecânico de microcisalhamento. As superfícies de esmalte vestibular de 56 incisivos bovinos íntegros foram aplainadas e divididas em 14 grupos. G. 01: foram confeccionados cilindros com sistema adesivo Single Bond (SB) e resina composta (RC) Z-250 (controle); G. 02: foram confeccionados cilindros com sistema adesivo Clearfil SE Bond (CF) e RC Z-250 (controle); G. 03: clareamento com Opalescence PF (Op) 10% e cilindros confeccionados com SB e RC, 12 horas após o término do tratamento clareador; G. 04: clareamento com Op 15% e cilindros confeccionados conforme descrito para 03; G. 05: clareamento com Op 20% e cilindros confeccionados conforme descrito para 03; G. 06: clareamento com Op 10% e cilindros confeccionados com CF e RC, 12 horas após o término do tratamento clareador; G. 07: clareamento com Op 15% e cilindros confeccionados conforme descrito para 06; G. 08: clareamento com Op 20% e cilindros confeccionados conforme descrito para 06; G. 09: clareamento com Op 10% e cilindros confeccionados com sistema adesivo SB e RC, 01 semana após o término do tratamento clareador; G. 10: clareamento com Op 15% e cilindros confeccionados conforme descrito para 09; G. 11: clareamento com Op 20% e cilindros confeccionados conforme descrito para 09; G. 12: clareamento com Op 10% e cilindros confeccionados com CF e RC, 01 semana após o término do tratamento clareador; G. 13: clareamento com Op 15% e cilindros confeccionados conforme descrito para 12; G. 14: clareamento com Op 20% e cilindros confeccionados conforme descrito para 12. As amostras dos grupos 03 a 14 foram clareadas durante 02 semanas (08 horas/dia). Os resultados obtidos mostraram que as médias de adesão dos grupos 03, 04, 05 e 06, 07, 08 foram estatisticamente menores (p0,05) às do respectivo grupo controle e tenderam a ser maiores que os valores de adesão obtidos nos cilindros confeccionados 12 horas após o término do clareamento, porém, em valores absolutos, a recuperação dos valores de adesão não foi completa (p0,05), independente da concentração do agente clareador, havendo recuperação dos baixos valores de adesão obtidos quando os cilindros foram confeccionados 12 horas após o término do tratamento clareador.The aim of this in vitro study was to evaluate the microshear bond strength of adhesive systems to bovine enamel surfaces previously submitted, or not, to bleach treatment with carbamide peroxide gel (Opalescence PF), in different concentrations (10%, 15% and 20%). The flat enamel surfaces of 56 bovine incisors were randomly divided in 14 groups. G. 01: cylinders made with Single Bond adhesive system (SB) and Z-250 composite (C) (control); G. 02: cylinders made with Clearfil SE Bond (CF) adhesive system and Z-250 (C) (control); G. 03: bleaching treatment with Opalescence PF (Op) 10% and cylinders made with SB and C, 12 hours after finishing the bleach regimen; G. 04: bleaching treatment with Op 15% and cylinders made according to 03; G. 05: bleaching treatment with Op 20% and cylinders made according to 03; G. 06: bleaching treatment with Op 10% and cylinders made with CF and C, 12 hours after finishing the bleach regimen; G. 07: bleaching treatment with Op 15% and cylinders made according to 06; G. 08: bleaching treatment with Op 20% and cylinders made according to 06; G. 09: bleaching treatment with Op 10% and cylinders made with SB and C, 01 week after finishing the bleach regimen; G. 10: bleaching treatment with Op 15% and cylinders made according to 09; G. 11: bleaching treatment with Op 20% and cylinders made according to 09; G. 12: bleaching treatment with Op 10% and cylinders made with CF and C, 01 week after finishing the bleach regimen; G. 13: bleaching treatment with Op 15% and cylinders made according to 12; G. 14: bleaching treatment with Op 20% and cylinders made according to 12. The specimens from groups 03 to 14 were bleached during 02 weeks, 08 hours/day, placed in individualized trays. During the remaining daily 16 hours, teeth were immersed in artificial saliva. Before microshear tests, the samples were stored in distilled water at 37 o C, for 24 hours. The results showed that bond strengths of groups 03, 04, 05 and 06, 07, 08 were statistically lower (p0,05) when compared with their respective control group and tended to be higher when compared with groups where adhesion were made 12 hours after the end of the bleaching treatment, with the same adhesive system. However, in absolute terms, the recuperation of the bond strength were incomplete (p0,05) when compared with their respective control group, recovering the bond strength values obtained when cylinders were made 12 hours after the end of the bleach regimen