Evaluation of the marginal fit of cobalt-chrome coping with three different fabrication.

Abstract

This study was done to evaluate and compare the marginal gap of metal coping fabricated in cobalt-chrome alloy using three different techniques of fabrication Casting, Milling and Direct Metal Laser Sintering. Typhodont premolar tooth was prepared to receive a porcelain-fused-to-metal crown. Metal replica (DIE) of this prepared premolar tooth was obtained and 6 pre-designated points were marked below the finish line on the die. The die was scanned digitally and coping was designed using the CAD software and STL file was obtained. The same STL file was used to fabricate 45 copings by3 different fabrication techniques of 15each. Group-1-Milled wax copings were casted, Group-2-Direct Laser Metal Sintered Copings and Group-3-Copings Milled directly from Chrome-Cobalt block. The marginal gap of each coping was evaluated on the metal die at 6 pre-designated points under stereo microscope at 40X magnification using custom made spring loaded jig assembly specifically made for this study. A total of 270 readings in µm obtained were statisticalyl analysed by One-way ANOVA and Turkey’s multiple post hoc procedures using SPSS software. A significant difference was found in the marginal gap of the copings fabricated by the three different techniques. The least marginal gap in the direct metal laser sintered copings Group-1: 95.12 (5.77 µm) followed by milled copings Group-2: 61.32 (2.94 µm) and casted copings Group-3: 83.50 (4.29 µm). Within limitations of the study best fit was in the direct laser metal sintering (DLMS) group followed by milled copings and milled wax coping which were casted.