Comparing the marginal and internal fit of metal copings fabricated by three different techniques.an in vitro study

Background: Marginal and internal fit play an important role in determining the longevity of the restoration. Several fabrication techniques have evolved in recent times, but little emphasis was advised to the fit of the restoration. Purpose: The aim of the study is to compare and evaluate the internal and marginal fit of Cobalt-Chromium copings fabricated by computer aided milling/computer aided designing, direct metal laser sintering and conventional casting method. Material and methods: A master metal Die was designed using CAD software and milled using Ni-Cr alloy. 3D printer was used to design a customized special tray for making impressions of master die. A total of 15 working dies were duplicated from the master metal die. The study included three groups of 15 samples in each. Group A copings were fabricated using conventional method, group B copings were fabricated using CAD/CAM procedure and group C included 15 copings fabricated using DMLS procedure. The silicone replica technique was used to measure the marginal and internal fit and these sections were visualized under stereomicroscope. Values were tabulated and statistical analysis was done using R- Software. The Kruskal Walis test was used to compare between groups. Results: Marginal and internal fit of all the groups were within the clinical acceptable range (˂120µm) and DMLS group showed least when compared to other groups. Conclusion: Both DMLS and CAD/CAM procedures resulted in producing lower discrepancies compared to Conventional group, however, further research and refinement in designing aspect is required in order to produce more precise restorations.