Evaluate the Vertical Marginal Discrepancy of Laser-sintered and Conventionally Cast Cobalt Chromium Crowns – An In vitro Study

A BSTRACT Background: Poor marginal adaptation of restoration resulting in damage to tooth structure, periodontal tissues, and the prosthesis. Purpose: To evaluate the vertical marginal discrepancy of laser sintered and conventionally cast cobalt chromium crowns. Materials and Methods: A stainless-steel cylindrical block of 30 mm height and 20 mm thickness was selected. Stainless-steel block was milled to a cylindrical metal die using computerized milling machine. The 20 virtual models are made using lava software and checked for undercuts and the luting agent space of 20 μm was simulated in virtual model. The finish lines are designed using computer-aided design (CAD) software. The virtual crowns 0.5 mm thickness was designed individually on all corresponding virtual dies. The CAD data of Group 1 samples were sent to the laser sintering machine (EOS). The CAD data of Group 2 models were sent to 5-axis milling machine. The 20 crowns of two groups were cemented to the respective dies with ZnP0 4 cement using finger pressure. The samples were then sectioned longitudinally with a diamond sectioning saw in an electrical sectioning machine. The measurements were made at four quadrants A, B, C, D following the guide marks on the dies. Results: The conventional cast samples showed significantly higher mean values in all the specific points A-l 77.5 μm, B-175.60 μm, C-175.3 μm, and D-177.9 μm, whereas the laser-sintered samples showed lesser mean values in A-102.5250 μm, B-104.152 μm, C-100.04 μm, and D-l l 6 μm. A statistically significant difference was noted in the vertical ga P values between the laser sintered and conventionally cast samples. Conclusion: Vertical marginal discrepancy between the laser-sintered cobalt chromium crowns and the conventionally cast cobalt chromium crowns was 104.35 ± 11.07 μm and 176.57 ± 12.58 μm. Vertical marginal discrepancy in laser-sintered crowns was less compared to crowns made from conventional method of casting.