In Vitro Comparison of Marginal Fit of All Metal, Porcelain Fused to Metal and All Ceramic Crowns

PURPOSE: To compare the marginal fit of all metal, porcelain fused to metal and all ceramic crowns fabricated using different materials and techniques commercially available. MATERIALS AND METHODS: 80 freshly extracted human mandibular first premolars were divided into 8 groups of 10 each which received Nickel-Chromium (Ni-Cr) all metal (AM) crowns, Cobalt-Chromium (Co-Cr) AM crowns, Ni-Cr three-quarter crowns, Co-Cr three quarter crowns, porcelain fused to metal (PFM) crowns with Ni-Cr copings, PFM crowns with Co-Cr copings, pressed all ceramic (AC) crowns and CAD/CAM fabricated AC crowns respectively. Crowns were cemented and specimen were sectioned buccolingually. The marginal gap was evaluated under a stereomicroscope. Lesser marginal gap indicated a better marginal fit. RESULTS: The mean marginal gap was maximum for Group 8 (222.3 μm) and least for Group 1 (85.5 μm). The mean marginal gaps for ‘all metal crowns’ and ‘metal ceramic crowns’ showed significantly lesser marginal gaps (p<0.05) for Ni-Cr Groups than Co-Cr Groups. When only ‘all ceramic crowns’ were compared, significantly lesser marginal gap was found for pressed AC crowns (148.6 μm) than CAD/CAM fabricated AC crowns (222.3 μm). CONCLUSION: Marginal fit of AM crowns were significantly better than PFM crowns and AC crowns. Ni-Cr group always showed better marginal fit than Co-Cr group. A better marginal fit of pressed AC crowns was seen than CAD/CAM fabricated AC crowns. Chamfer finish line showed a significantly better marginal fit than shoulder finish line.