The Accuracy of Fit of Crowns Made From Wax Patterns Produced Conventionally (Hand Formed) and Via CAD/CAM Technology.

Abstract

The aim of this study was to compare the marginal and internal fit accuracy of crowns constructed using three different wax production methods; conventional, milled, and 3D printed and utilizing three different cement gap thicknesses. 15 identical stone dies were made for each method. Wax patterns were produced and then cast into metal crowns, which were assessed for differences in accuracy of both marginal and internal fit. Measurement points were 4 points per crown; occlusal, axial, marginal gap, and marginal discrepancy points. A silicone impression technique and conventional cementation technique were employed to facilitate the measurements. There was no significant difference (p > 0.05) in accuracy between the digitally and manually produced crowns, with the 3D printed crowns being slightly more accurate. Whereas, statistically significant differences were noticed between the conventional versus printed groups, in occlusal and marginal gap points (p < 0.05). The marginal and internal fit of 3D printed wax patterns is more accurate than the other two production methods. The milling of wax crowns is as accurate as the conventional hand carved production in terms of internal and marginal fit. The manufacturer recommended offset/die-spacer of 30 μm produced the most accurate internal and marginal fits.