Replica patterns on composite restorations performed in vivo with different acid-etch restorative procedures

243 experimental Class V restorations using a chemically cured composite resin were inserted in human third molars with the conventional acid-etch restorative procedure and eight modifications of this technique. The teeth were extracted after 4 months and, following demineralization, the filings were examined in SEM concerning their enamel and dentin replica patterns on the inner cavity faced surface. Results showed a significant correlation between the enamel replica patterns and the marginal adaptation of the restorations while the dentin replica patterns did not influence the in vivo adaptation. Furthermore it was found that the improved adaptation obtained by low viscous resin applied as an intermediary layer in etched cavities is due to fewer porosities in the restorative material interface with enamel and dentin. Beveling of preparations prevents stress-induced fractures of unsupported enamel prisms along the cavity periphery. Treatment of etched cavities with the surface active comonomer NPG-GMA increases the general interfacial contact between resin restoratives and cavity walls, and surface coating of finished and re-etched restorations fills up spaces created along cavity margins during the filling and finishing procedure.