Introduction
fracture, brittle
Tooth-colored restorations are considered a primary requirement for dentist and patient because of biocompatibility and esthetics characteristics which are the main reasons for using dental ceramics as a preferred material for inlays in present time [Ceramic inlay is accepted clinically as a restoration for posterior teeth with extended coronal destruction and became a substitute for dental alloys [The bond between ceramic inlays and the tooth structure along with the mechanical friction are major roles of success for inlays retention [In addition to conventional impressions, digital impressions are used as they are faster with reduction of the workflow steps and better tolerability by the patient. Moreover, the virtual scan file can be transferred to the lab through certain applications, without fabrication of a die or providing clinical bite registration [According to the type of restoration, the highest clinically marginal gap width values that is acceptable was suggested in the previous literature [Ceramic materials are known to be brittle and more liable for fracture, still harder than composite based materials, therefore ceramics are more wear resistant. On the contrary, they may cause wear of the opposing tooth surface [Therefore, this study aimed to analyze the effect of varieties of CAD-CAM materials on marginal gap of inlay restorations before and after thermocycling. The null hypothesis supposed firstly that “there would be no significant difference in the marginal gap between the milled CAD-CAM inlays from 3 CAD-CAM” and secondly that “This would not change after thermocycling”.