Influence of Material Layer Deposition Thickness, Span Length of Prosthesis, and type of Laser on the Surface Marginal fit of Different Surfaces of DMLS copings Fabricated using 3 Different DMLS Printing Machines
Background: Metal-ceramic restorations are frequently made using laser sintering. The sintering process' layer thickness may have an impact on restoration adaptation. However, there is little information about its impact. Aim: The goal of this in vitro experiment was to compare the marginal adaptation of laser-sintered cobalt-chromium long span bridges and single crown frameworks made on different DMLS machines. Methods: Tooth preparation was carried out on a typhodont teeth set from 14-22 and for 16. The dies were scanned and the samples were designed using 3 Shape software. The samples were then laser sintered using 3 different DMLS machines. Sample size consisted of 6 samples for the long span framework and 6 samples for the single crown framework per machine. Marginal accuracy was evaluated at 6 different points (mesiobuccal, buccal, distobuccal, mesiopalatal, palatal and distoplatal surface). The microscopic evaluation was carried out using a stereomicroscope. The discrepancy and internal fit values were recorded and tabulated. Spss version 20 software was used to carry out statistical analysis. Descriptive ANOVA test followed by Benferroni test was used to evaluate the statistical significance. Results: The proximal surfaces showed higher discrepancy levels as compared to the other surfaces. The mean values of the marginal discrepancy values were comparatively higher on the proximal surfaces (mesiobuccal, mesiopalatal, distobuccal and distopalatal points) as compared to the buccal and palatal surfaces (buccal and palatal points). There was a statistically significant difference in the marginal discrepancy values of the dmls copings fabricated using different DMLS printing machines on the mesiopalatal, distopalatal and distobuccal surfaces (P value <0.05). Conclusions: Best marginal fit values were achieved with the EOS machine suggesting that the metal deposition layer thickness as well as the type of laser did have a significant impact on the marginal fit of the prosthesis. The proximal surfaces showed higher discrepancy levels as compared to the other surfaces again questioning the accuracy of the scanner, designing software and the DMLS machines. The span length did have an impact on the overall fit of the prosthesis suggesting that there might be errors incorporated during the scanning or during the metal printing.