Effect of manufacturing type and aging on the fit of metal frameworks: an in vitro Micro-CT study

It is very important to determine how the marginal and internal fit of the restoration just before cementation changes after the specified period and which technique preserves the fit of the metal framework, and it has not been discussed in the literature.

This in vitro study aims to evaluate the effect of conventional casting, CAD/CAM milling, and laser sintering manufacturing methods on the marginal and internal fit of Co-Cr metal frameworks and how the fit will be affected following thermomechanical aging using Micro-CT.

Digital impressions were taken from the prepared typodont and metal frameworks were designed with ExoCAD software. Co-Cr metal frameworks were manufactured with 3 production methods (n = 15). In order to reflect the clinical conditions, a ceramic firing simulation was performed on metal frameworks. Thermomechanical aging was applied to the samples, equivalent to 1 year of use. For statistical comparison, the differences between the manufacturing techniques ANOVA followed by Tukey and, for aging Wilcoxon Test were used (α = 0.05).

Compared to the conventional casting method, computer-aided methods showed a better fit. Thermomechanical aging increased misfit in all three production methods. At all determined points, before and after aging, the highest gaps were measured in the conventional casting method. In volumetric evaluations, both before and after aging, it was seen that the highest fit was in the laser sintering method, and the lowest fit was in the conventional casting method.

Production technique and aging have an impact on the fit of metal substructures. Following aging, misfit increased more in computer aided manufacturing than conventional casting.