Proximo-cervical adaptation of Class II-composite restorations after thermocycling: a quantitative and qualitative study.

Sixty caries-free extracted human molars were used to determine the proximo-cervical adaptation and sealing of Class II-composite restorations related to the location of the cavity margins: 1.0 mm or 0.5 mm coronal to the cementum-enamel-junction (CEJ), at the CEJ, and 0.5 mm apical to the CEJ. All cavities were filled with a hybride type composite resin, which was combined at the CEJ and apical to the CEJ with a dentine adhesive in half of the specimens. The proximo-cervical adaptation and sealing was determined before and after thermocycling (TC, 2000 cycles, 5-55 degrees C) by SEM and dye penetration tests. Furthermore, an analysis of the interfaces between the enamel or dentine and the filling material was performed to determine whether or not there is a significant correlation between micromorphological factors of the dental hard tissues (enamel acid etch pattern, dentine resin tag pattern) and the marginal adaptation of the composite restorations. The data were statistically evaluated by means of H-tests (Kruskall-Wallis), U-tests (Mann-Whitney), and Chi2-tests (P < 0.05). It was found that the proximo-cervical adaptation is statistically significant dependent on the position of the margin. 1.0 mm coronal to the CEJ an excellent marginal sealing was found before and after TC, whereas all other groups revealed a significant deterioration of the marginal integrity after TC. Using a dentine adhesive significantly improved the marginal sealing in cavities at the CEJ before and after TC, however the marginal quality was not achieved as in the case of the normally structured enamel 1.0 mm coronal to the CEJ following acid etching. In defects 0.5 mm apical to the CEJ the dentine adhesive only improved the cervical adaptation before TC. The evaluation of the tooth/filling interfaces revealed that there is no statistically significant correlation between the enamel acid etch pattern resp. dentine resin tag pattern and the marginal sealing.