Marginal adaptation of composite resin restorations placed with or without intermediate low-viscous resin. An SEM...

The marginal adaptation to acid-etched enamel of a hybrid and a microfilled composite resin, placed with or without intermediate low-viscous resin, was investigated in vivo. Each of 37 patients received four class III test fillings, one with each filling technique. The evaluation was done with the use of SEM on replicas from the cavity margins, 1 week and 1 year after insertion of the fillings. The observed defects were marginal cracks or fractures, chip fractures, and enamel fractures. In the comparison of the size and volume of the marginal defects no significant differences were seen after 1 week between fillings of the same material placed with or without an intermediate resin. However, after 1 year the hybrid resin fillings with an intermediate resin showed significantly better adaptation than the ones without. No difference was found between the microfilled resin fillings. The hybrid resin fillings showed significantly better marginal adaptation than the microfilled resin fillings after 1 week. A further increase of the differences was observed after 1 year.