Objective: The purpose of this study was to evaluate the marginal fitness of the porcelain-fused Titanium crowns by using a CAD/CAM system (Smart-Fit, DCS Dental AG) compared to the conventional casted pure Titanium crowns. Methods: A stainless steel master die was machined to simulate a mandibular second premolar rounded shoulder preparation. A total number of 11 impressions were made and poured using type ‡W dental stone(Super-Rock, Noritake). The stone dies were divided into three groups:1 for Smart-Fit crowns;5 for casted pure Titanium crowns ; and 5 for porcelain-fused-to-metal (PFM) crowns. In the Smart-Fit system, 5 Titanium crown frames were available from a die using computer-controlled milling machine. The marginal fitness of each restoration was examined at 100-fold magnification using a micro depth and height measuring scope(Nissho Optical Co. Ltd. Japan). The gap between the margin of the restoration and the margin of the preparation on the stainless steel master die was measured. Measurements were made in four points :buccal,palatal,mesial and distal sides.Each surface was measured six times randomely. The data (mean±SD,µm) were statistically analyzed with one-way ANOVA at P = 0.05 then Tukey HSD post-hoc test were performed (p<0.05). Results: The PFM crowns (control) exhibited the smallest marginal gaps(16.4±3.2 µm), followed by Smart-Fit metal-ceramic crowns(17.0±4.5µm) and casted Titanium crowns(68.2±14.7µm). There were no significant differences between crowns fabricated from Smart-Fit system and PFM crowns. Moreover there were no significant differences between the stages of the crown fabrication: core fabrication and porcelain veneering through glazing not only in PFM crowns(14.8±2.7µm) but also in Smart-Fit crowns(14.6±2.7µm). Conclusion: Smart-Fit system has no significant difference in marginal accuracy with the PFM crown and during the fabricating stages .

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