the objective of the present in vitro study was to evaluate the effect of two different CAD/CAM systems on the marginal fit of three commercially available dental ceramics using micro-computed tomography. Materials and Methods: one human natural premolar was selected, received a standardized all ceramic preparation and duplicated using two types of die materials. PMMA dies were used for construction of E.max CAD and Vita Enamic monolithic crowns while zirconia dies were used for zirconia crowns. A total of thirty monolithic all-ceramic crowns (N=30) were constructed on the fabricated working dies. These were equally divided into 2 groups (n=15) according to the CAD/CAM system used as follows: group (I): Everest system and group (II): Zircon Zhan system. Each group was further subdivided into 3 subgroups (n=5) according to the ceramic material used into subgroup (E): E.max CAD glass ceramic, subgroup (Z): ice prettau zirconia and subgroup (V): Vita Enamic hybrid ceramic. Each sample was scanned for fit analysis using a quantitative micro-computed tomography scanner then were analyzed. Results: Everest CAD/CAM system showed statistically significantly lower mean marginal gap distance than ZirconZahn. Either with Everest or ZirconZahn; E.max CAD showed the statistically significantly highest mean vertical marginal gap distance followed by Zirconia while Vita Enamic showed the statistically significantly lowest mean vertical marginal gap distance.
Conclusions: Micro-CT technology presents a reliable tool for evaluation of the dental restorations fit. Also, superior marginal fit is achievable with monolithic CAD/CAM hybrid ceramic compared to both zirconia based and glass ceramics