Abstract
The incomplete removal of the smear layer observed with self-etch adhesives systems may negatively affect hybridization. Studies have shown increase in the bond strength after complete removal with deproteinizing agents. In addition, the use of a remineralizing material could decrease the amount of dentin removed in cavity preparations. Thus, considering the results from previous studies and the search for alternative methods using natural substances to increase the longevity of the hybrid layer and, consequently, of the restoration, the aim of this study is to evaluate the effect of the use of bromelain extract associated with Biosilicate on the bond strength (BS) of composite restorations to sound and caries-affected dentin. To determine the concentration of bromelain, time and method of application that will provide the best performance, a previous study will be carried out using the extract at different concentrations (0, 2%, 5% and 10%), associated with 10% Biosilicate or not, applying it for 30 seconds and 1 minute, with a microbrush or a pipette, according to each group. Then, the substrate will be characterized by scanning electron microscopy (SEM, EVO MA10, ZEISS). The results found in this preliminary study will support the selection of two concentrations, as well as, the time and method of application, that will serve as protocol for evaluation of the bond strength. For that, sound human molars will be selected, and occlusal cavities will be prepared (5 mm x 4 mm x 2 mm) using carbide burs. Half of them will be submitted to formation of caries by biological model with S. mutans strain ATCC25175. Afterwards, all teeth will be separated into groups, according to the treatment received before the adhesive system (Single Bond Universal, 3M ESPE): Control Group - Adhesive System; CHX Group - 0, 12% Chlorhexidine; NaOCl Group - 5% Sodium hypochlorite; Br Group -Bromelain extract; Bio Group - 10% Biosilicate suspension; NaOClBio Group - NaOCl + Bio; BrBio Group - Br + Bio. After restorative procedures (Filtek Z350XT, 3M ESPE), the samples will be sectioned into sticks, separated and stored in distilled water at 37 °C for 24 hours, 6 months and 1 year. After these periods of storage, they will be submitted to microtensile test (0.5 mm/min). Data will be analyzed according to the most appropriate statistical test. The fracture patterns will be observed with digital microscope (VH-M100) and the adhesive interface by scanning electron microscopy (JSM 5410, Sony) and transmission electron microscopy (JEM-1010, JEOL). Likewise, the biodegradation test of the dentin matrix and in situ zymography (Leica DMI 6000) will be performed. (AU)