Evaluation and Comparison of Internal Fit of Cobalt-Chromium Copings Cast from Milled Wax and Milled PMMA Patterns Fabricated Using CAD/CAM Technology- an in Vitro Study.

Abstract

PURPOSE

This study aimed  to evaluate and compare internal fit of Cobalt- Chromium copings cast from milled wax and milled PMMA patterns fabricated using CAD/CAM technology

MATERIALS AND METODS

After selection of 30 ivory teeth , they were prepared for the master model. A custom tray was fabricated to make impressions of prepared ivory teeth . One- step double- mix elastomeric impression technique was used for the impression then poured with a Type IV die stone. The procedure was repeated thirty times to obtain dies of same dimensions for milled wax and milled PMMA patterns. Then the metal copings were fabricated and seated onto the stone die and fixed with commercially available Glass Ionomer Cement. All the copings were sectioned longitudinally in buccolingual direction using diamond disc and seen using stereomicroscope in 40X.

RESULTS

On comparative statistics of internal gap/ discrepancy between Group A (Milled wax) and Group B (Milled PMMA) respectively, there was found to be highly statistical difference  (p<0.001) between both groups, Milled PMMA had better internal fit as compared to Milled wax.

CONCLUSION 

Since the results obtained in this study using Group A (copings casted from milled wax patterns) and Group B (copings casted from milled PMMA patterns) were comparable and within acceptable limits, all of these Cobalt-Chromium copings casted from milled wax patterns and milled PMMA patterns can be considered for further clinical evaluation.