Evaluation of the marginal discrepancy of cobalt chromium metal copings fabricated with additive and subtractive techniques

Abstract

Aim: The aim of this article was to compare the marginal discrepancy of CoCr metal coping fabricated by three techniques, namely (A) direct CAD/CAM milling, (B) casted milled CAD/CAM wax, and (C) direct metal laser sintering (DMLS) technique. Materials and Methods: A comparative study between additive and subtractive manufacturing techniques was made. The study involves three groups; 15 metal copings were made for each group. Standardization was done by using the same STL file for all groups. With group A, direct milling was done to the CoCr blank. Group B follows the conventional casting method for wax framework milled by a CAD/CAM machine. Group C metal coping was made by the DMLS technique. The measurement of marginal discrepancy was done to four aspects: buccal, palatal, mesial, and distal using a digital light traveling microscope with magnification power of 200×. Statistical analysis used was one-way analysis of variance test and Tukey’s test. Results: The mean vertical marginal discrepancies for groups A, B, and C were 19.070, 23.470, and 38.533 μm, respectively. Statistical analysis shows a very high significant difference among groups (P < 0.001). Conclusion: All the tested groups showed an acceptable marginal discrepancy. The direct CAD/CAM metal milling method results in minimum marginal gaps when compared with additive and subtractive techniques.