Influence of gingival contour on marginal fit of CAD-CAM zirconia copings on implant stock abutments

Abstract

Intraoral scanning subgingival finish lines has been described as challenging. The purpose of this study was to assess the impact of gingival contour around margins of implant stock abutments on marginal fit of Computer-aided Design – Computer-aided Manufacturing (CAD-CAM) zirconia copings. This in-vitro study was conducted on 40 analogues of implant stock abutments that were embedded into individual phantoms composed by a resin block. All 40 phantoms underwent two intraoral scans – one with (test group) and one without artificial gingiva (control group) – using a closed system intraoral scanner. Zirconia copings were then digitally designed and milled, followed by high-speed sintering, before being analyzed for marginal adaptation and internal surface roughness with scanning electron microscopy. Statistically significant differences between groups were assessed with the Mann-Whitney test. Median marginal gap values were 149.78 μm (95% CI: 112.39-216.66) for the test group and 94.90 μm (95% CI: 83.89-107.74) for the control group. A statistically significant difference was found between groups (p=0.0001). However, there were no subjective differences between groups for internal surface roughness. Within the limitations of this study, the present findings suggest that a gingival contour one millimeter higher than the finishing line affects marginal adaptation of CAD-CAM zirconia copings.