Marginal accuracy of metallic copings fabricated by different wax pattern techniques

Objectives: To evaluate marginal accuracy of metallic copings fabricated by conventional lost wax, CAD CAM technique using stereomicroscope. Methods: A stainless steel die was used with preparation height of 7 mm., finish line of 1.0 and the axial convergence was 5 degrees. Seven polyether impressions of the die were made and poured to extra hard stone to produce dies. Upon each die two types of wax pattern were fabricated, Group I: copings were fabricated manually. Group II: copings were fabricated using Cercon CAD/CAM machine creating 30 copings from the two groups (15 each group). All wax patterns were invested and casted to Nickel-chromium alloy Marginal gap was tested on 4 points around the copings using stereomicroscope. Paired t-test was used to analyze data P value lower than 0.05 considered statistically significant. Results: there was statistically significant difference between tested groups, The mean (SD) for the marginal gap were 109.85(24.71), 115.97 (25.65) for manual and CAD/CAM fabricated wax patterns respectively. Conclusion: With the limitations of this study, the conventional fabricated wax patterns (group I) gives significantly better marginal gap than CAD/CAM (machine-milled) technique (group II).