Efeito da remoção de colágeno e da termociclagem na resistência de união de dois adesivos convencionais à dentina

Abstract

The increase of the adhesive infiltration in the dentin may reduce the gaps in bond interface. The sodium hypochlorite (NaOCl) has been employed for removing the demineralized dentin collagen, transforming it into a more permeable substrate, thus facilitating the diffusion of the adhesive resins intra and intertubular level. Objective: To assess the effect of dentin collagen removal by 10% NaOCl for 60 s on microtensile bond strength of two simplified conventional adhesive systems to this substrate, immediately after or after thermocycling. Methods: Forty freshly extracted third molars had the dentin surface exposed and were divided into four groups according to the type of adhesive solvent used (water/ethanol - Adper Single Bond 2 or acetone - Stae) and the proposed dentin surface treatment (acid-etch or acid-etched + 10% NaOCl). Then, the restoration incrementally with resin Z100 (3M ESPE) was performed. After 24 hours of storage in distilled water at 37 ºC all teeth were sectioned for microtensile test. The specimens in each group were subdivided into two subgroups: immediate test and test after 10,000 cycles. µTBS data were analyzed by two-way ANOVA and Tukey´s test (p<0.05). Failure mode was analyzed and classified as cohesive in dentin, cohesive in resin and mixed/adhesive. Results: The use of NaOCl resulted in a significant decrease on immediate and long-term microtensile bond strength for Single Bond 2 (p<0.001), while Stae was unaffected by the deproteinization and the thermocycling (p=0.194). Conclusion: The collagen removal promoted by 10% NaOCl for 60 s as well as the thermocycling, showed an adverse effect for the water/ethanol-based adhesive. These treatments have no influence on the microtensile bond strength of acetone-based adhesive to dentin.