Evaluation of marginal accuracy of nickel chromium copings fabricated from three different fabrication techniques: an in vitro study

Abstract

The purpose of the study was to compare the marginal accuracy of Ni-Cr copings made by four different pattern forming methods, using inlay casting wax and pattern resin in the conventional manner, inlay wax patterns by CAD & milling and resin patterns made by a 3 dimensional printing (3DP) technology a total of 40 test samples of Ni-Cr cast copings were made out of 10 patterns of each group using inlay casting wax, pattern resin, inlay wax by CAD and milling and from pattern resin by 3D printing technology. Each cast coping was seated on the stainless steel die and was evaluated for both vertical and horizontal marginal gaps using a translating tool makers microscope. The vertical marginal gap data was analyzed by use of Kruskal Wallis Test followed by Mann Whitney U Test and the horizontal marginal gap data was analyzed by using ANOVA followed by Tukey honestly significantly different (HSD) tests. 3D printed resin pattern copings showed better results of marginal adaptability. marginal fit of the Ni-Cr cast copings fabricated from the patterns prepared from inlay casting wax, pattern resin, CAD milling and 3 dimensional printing (3DP) technology were in the clinically acceptable range for longevity of restorations.