The purpose of this in vivo study was to compare the marginal and internal gap widths of monolithic zirconia crowns fabricated by CAD/CAM technique and metal-ceramic crowns fabricated by conventional technique. Materials and methods: 10 participants needing a single restoration were selected. Zirconia crowns using CAD/ CAM technology (Group A) (n=10) and metal-ceramic crowns (Group B) (n=10) using lost wax casting technique were fabricated for each selected tooth. The marginal and internal gaps

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... of crowns were recorded using a replica technique with light body silicone material stabilized with a regular set putty. Each replica was sectioned buccolingually and mesiodistally and then evaluated at five pre-determined sites. The points measured were PM for marginal gap, PA for axial gap, PAO for axio-occlusal transition gap and PO and PCO for occlusal gaps using a stereomicroscope at 30× magnification. The Paired Sample (t) test was used to detect significant differences between the two groups in terms of marginal and internal fit (α= 0.05). Results: The mean for the marginal gap was 77.42μm (±39.5μm) for Group A compared with 95.86μm (±55.12μm) for Group B. Mean values for internal gap was 87.24 (±21.7 µm) for Group A and 132.91 µm (± 50.63 µm) for Group B. Significant differences were observed between both the groups for marginal (p=.010) and internal (p=.000) fit. Conclusions: The CAD/CAM fabricated zirconia crowns demonstrated a better accuracy of fit when compared to metal-ceramic crowns fabricated by conventional technology.