Abstract: Objective To evaluate the influence of different types of cements and thermocycling on marginal adaptation and fracture strength of Ceramage ceramic optimized polymer（ceromer） crowns. Methods Sixteen ceromer
crowns and sixteen metal-ceramic crowns were fabricated. Eight specimens of each crown type were cemented, using either glass ionomer cement（GI） or adhesive resin cement（AR）. All crowns were exposed to 5 000 thermal cycles between 5 ℃ and 55 ℃. The marginal adaptation were evaluated with a stereomicroscope. The fracture strength of the crowns were measured with universal testing machine. Results The marginal adaptation of ceromer crowns was statistically better than metal-ceramic crowns（P<0.05）. The mean marginal gap increased significantly after cementation in all groups（P<0.05）. The thermocycling did not result in a significant rise of the marginal gap of crowns（P>0.05）. The fracture strength of ceromer crowns was significantly lower than metal-ceramic crowns（P <0.05）. Conclusion Within the limits of this in vitro study it could be concluded that the marginal adaptation of ceromer crowns was better than metal-ceramic crowns. The fracture stre ngth of ceromer crowns exceeded normal occlusal forces. Adhesive resin cement improved the fracture strength of ceromer crowns.

Key words: marginal adaptation, fracture strength, thermocycling