Comparison of the Marginal Fitness of Feldespatic all Ceramic Crowns with Two Finish Lines (Chamfer and Shoulder) Fabricated by CAD/CAM System

To study the effect of tooth preparation on marginal adaptation of all-ceramic crown designed by the CAD/CAM system.
Subjects and Twenty master dies (height: 7 mm, Ø: 5mm, conicity: 10°) with different finish lines (chamfer 50° finish line 0.8 mm depth) and (shoulder 90 degree with rounded axiogingival internal line angel 1mm depth) were manufactured. Ten impressions were made from each master die using Vinyl polysiloxane. Impressions were poured in type IV dental stone, and 20 ceramic crowns were subsequently milled with cad cam.The crowns were fixed on their respective metallic die using a metallic fixation device. The marginal discrepancy was measured at 60 points on the respective metallic die by using stereomicroscope. The data were analyzed using ANOVA and t test (P Significant difference was observed between marginal discrepancy of 2 groups (chamfer: 75.595 ± 2.119 micron, and shoulder: 81.656 ± 2.127 micron, P>0.05). Marginal design with chamfer is better than shoulder. In shoulder design significant difference was observed between buccal surface and mesial surface, mesial surface and lingual surface P0.05 no significant different was observed between other surface.
Marginal discrepancy at the shoulder design is more than chamfer design and the T test was shown significant marginal gap in shoulder design preparation versus chamfer design preparation.