Marginal discrepancy of 3-unit Co-Cr metal copings fabricated with additive and subtractive manners: A comparative study.

Abstract

Poor marginal adaptation may give rise to a series of biological complications. Despite its importance, comparative studies on marginal adaptation of metal-ceramic fixed restorations fabricated with newer methods are limited. Therefore, it was aimed to assess the marginal accuracy of copings fabricated with subtractive and additive manners used in contemporary dentistry. For a typodont model, 60 three-unit cobalt-chrome metal copings were fabricated by selective laser sintering (SLS), hard alloy milling (HAM), and soft alloy milling (SAM) in comparison to casting (C). Marginal discrepancy assessment was performed by using replication technique. Mesiodistal and buccopalatal cross-sections of silicone replicas were investigated under a stereomicroscope at × 80 magnification. A total of 960 measurements were subsequently made by means of corresponding image-review software on captured images after calibration of the software to μm scale. Obtained data were subjected to nonparametric Kruskal Wallis and Tamhane post-hoc tests (α =0.05). Marginal adaptation of C group was significantly inferior to test groups in both canine- and premolar-teeth measurements (P < 0.05). Marginal fit was found to be tooth dependent (P < 0.001). HAM, SAM, and SLS groups exhibited analogous marginal discrepancy values on canine-tooth measurements. Differences among these groups were not statistically significant (P > 0.05). SAM and SLS groups demonstrated better marginal adaptation than others on premolar-tooth measurements. Also, no statistically significant difference was detected between SAM and SLS groups (P > 0.05). SAM group demonstrated superior marginal accuracy. All groups had clinically acceptable marginal discrepancy values (<120 μm), except cast group.