RESUMO
PURPOSE: To investigate in situ the influence of gaps in the development of secondary caries lesion in adhesive restorations. METHODS: 10 volunteers utilized intra-oral appliances, containing three human dental blocks (enamel and dentin), representing the three different groups (two restored, one sound): (1) restored with resin composite using the total acid etch adhesive technique (37% H3PO4 + Single Bond + Z250); (2) restored with resin composite but without acid etching (Single Bond + Z250); (3) and sound blocks (control group). The dental blocks (n=30) were randomly positioned inside the intra-oral appliances, and covered by a porous tissue (gabardine base) to induce a cariogenic biofilm. The volunteers used the appliances 24 hours daily for a 28-day period, removing just during meals and oral hygiene. Eight times a day, a 20% sucrose solution was dripped onto the blocks. Five minutes later, the appliance was washed with distilled water and replaced in the oral environment. After the experimental period, the dental blocks were removed from the appliance and examined by visual examination to detect the presence or the absence of an active carious lesion (kappa= 0.89). Posteriorly, they were prepared for the polarized light microscopy examination, which was performed to describe enamel surface characteristics on the restored and unrestored blocks with active caries lesion (kappa= 1). RESULTS: The visual examination demonstrated that almost all (29/30) of the blocks showed non-cavitated active caries lesion on the enamel surface. The microscopic evaluation showed non-cavitated caries lesions on enamel surfaces for all groups. In the restored blocks (with and without the total etch technique), the demineralization was first identified as an outer lesion that follows the enamel prism directions, and in some cases, reached the cavity walls. The results showed that caries lesion development adjacent to the restoration was determined by the cariogenic challenge of the oral environment, instead of the restoration adhesive quality, and the wall lesion was determined by the prism orientation, regardless of the presence of gaps.