1 Microleakage may lead to problems such as postoperative sensiti

1 Microleakage may lead to problems such as postoperative sensitivity, marginal discoloration and breakdown at the tooth-restoration interface, recurrent caries and pathological changes of the pulp tissue.2�C5 Enzalutamide Cavity type and design and the localization of the restoration may affect the microleakage pattern. An enamel bevel along the margins of the facial and lingual vertical walls of Class II cavities prepared for resin-based composite restorations has been shown to minimize the microleakage of the vertical and also the gingival margins.6 Today, the progress in adhesive dentistry has led to the improvement of the marginal integrity and consequently the clinical performance of dental restorations. However, microleakage still remains to be a clinical problem.

Restorations with margins in gingival region and especially located below the cement-enamel junction exhibit still difficulties in achieving properly sealed restorative margins even with esthetic restorative materials using newly developed effective adhesive systems.7�C13 Ormocers are organically modified ceramic materials which have been recently developed restorative systems and claimed by the manufacturer to have a high biocompatibility, a less polymerization shrinkage which is related to the size of the monomer molecules, a high adhesion to dentine and enamel and a proper marginal tight for all classes of cavities. Several past studies investigated microleakage pattern using only thermocycling procedure in their materials and methods. To simulate oral masticatory forces however, load cycling procedure alone or together with thermocycling were also used in recent studies.

The findings of all of these studies which evaluated different restorative systems with different cavity types revealed contradictory results on the role and effects of thermocycling and load cycling on micro-and nanoleakage.14�C31 Rigsby et al27 found that the microleakage at the cementum aspects of composite resin restorations subjected to both temperature cycling and occlusal loading was significantly more than the ones subjected to only temperature or load cycling. Jang et al20 also showed that application of load cycling in conjunction with thermocycling significantly increased the microleakage.

The objective of this in vitro study was twofold: 1) To assess the marginal sealing ability of an ormocer compared with that of a hybrid composite in box-only Class II cavities, and 2) to evaluate the effect of thermocycling and load cycling applied together during the Carfilzomib testing procedure on the pattern of microleakage. MATERIALS AND METHODS Twenty-two human premolars extracted due to orthodontic reasons were used in this study. They were free from caries and/or restorations and had no developmental defects. Proximal box-only Class II composite cavities with occlusal bevels of approximately 0.5 mm were prepared on the mesial and distal surfaces of each tooth.

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