Internal Fit of Cobalt–Chromium Metal–Ceramic Crowns Fabricated by Conventional Casting and Selective Laser Sintering: An In Vitro Comparison of Three Measurement Techniques

Abstract

1.Background/Objectives: The purpose of this study was to compare the internal fit of cobalt-chromium metal-ceramic single crowns fabricated through conventional casting versus selective laser sintering (SLS), and to determinate the relative accuracy of three internal space measurement techniques. 2.Methods: A standardized CAD design of a maxillary first molar was used to create two metal frameworks, one produced by was-pattern milling followed by casting and the other by SLS. Internal fit was assessed before and after ceramic firing using methods: differential micrometer measurements on frameworks with and without impression material, direct micrometer readings of detached silicons replicas, and digital microscopy of sectioned silicone specimens. 3.Results: All methods revealed measurable differences in internal adaptation between the cast and SLS crown. Digital microscopy offered the highest precision and consistency, while micrometer-based techniques showed greater operator- dependent variability and were influenced by the elastic behaviour of the silicone impression material. Ceramic firing did not introduce clinically relevant changes in internal space. 4. Conclusions: Within the limitation of the study, conventionally cast frameworks demonstrated a more favourable internal fit than SLS frameworks, and digital microscopy proved to be the most reliable method for evaluating internal adaptation in metal-ceramic crowns.