CADCAM V/S CONVENTIONAL TECHNIQUE FOR BETTER MARGINAL FIT OF METAL COPINGS FROM WAX PATTERNS

Aim: To evaluate and compare the marginal gap of metal copings cast from wax patterns fabricated with conventional technique and CAD/CAM technique. Materials and Method: Fifty samples were fabricated using Standardized MIS implant abutment as a die. 25 wax patterns (n=25) were fabricated by conventional wax coping method and rest (n=25) were fabricated by CAD/CAM wax milling technique. The wax copings of both the methods are casted with conventional casting technique. The marginal gap of copings was evaluated by direct view technique under stereomicroscope (MAGNUS) with digital camera. Then images were transferred to personal computer for measuring marginal gap at 15 random points by using image analyzer (IMAGE PRO EXPRESS 6.0). Statistical data was calculated and further analyzed by unpaired student t-test (α=0.05). Results: This study showed an overall mean of 595.26 ?m for absolute marginal discrepancy (AMD) with Standard deviation of 264.94 for CAD/CAM group and 233.42 um with Standard deviation of 184.98 for conventional group (control). Unpaired T-Test revealed that marginal gap was significantly higher in CAD CAM group than the conventional wax-up group. Conclusions: Within limitations of this study conventional method of wax pattern fabrication produced copings with significantly better marginal fit than CAD/CAM technique. All the factors for 2 groups were standardized except wax pattern fabrication technique therefore only the conventional group results in copings with clinically acceptable margins of less than 300 microns. Advancement in digital dentistry has improved the ease and quality of restoration in dental lab but still needs a technical improvement in scanning procedure, data processing and milling technology. Clinical Significance: The long-term success rate of metal ceramic crown is determined by the proper marginal fit between the restoration and the prepared tooth. The improper fit or marginal discrepancy leads to secondary caries which accounts for 85% failures in fixed partial dentures. Even though digital technology has radically emerged into the dental laboratory procedures to improve the quality of restorations, this study reveals conventional wax up and casting procedure showed better marginal fit as compared to CAD-CAM system.