Aim: The purpose of this study was to compare the accuracy of intraoral scanning on a tooth model according to four finish line conditions (supragingival, equigingival, subgingival, and subgingival with gingival cord).
Materials and methods: To simulate the clinical situation, the abutment was fabricated using ceramic materials. A pigment was added to the transparent orthodontic silicone to create a translucent gingiva. A CAD reference model (CRM) was obtained using a contact scanner. Finish lines on the tooth preparation were placed at the subgingival (0.5 mm below the level of the gingiva), equigingival, and supragingival (0.5 mm above the level of the gingiva) locations. In addition, a gingival cord was packed into the gingival sulcus below the subgingival finish line. A CAD test model (CTM) was obtained using two types of intraoral scanners (IOSs), i500 (Medit) and EZIS PO (DDS; N = 20 per locations). CRM and CTM were superimposed and analyzed using 3D analysis software. In the statistical analysis, the comparison of accuracy according to the finish line locations was confirmed by one-way ANOVA (α = 0.05). The differences between the groups were analyzed using the Tukey HSD post-hoc test.
Result: There was a significant difference in the accuracy of intraoral scanning according to the finish line locations of the tooth preparations (P < 0.001). The equigingival and subgingival finish lines showed poor accuracy. The use of gingival cords significantly improved the accuracy (P < 0.05). There were significant differences between the two types of IOSs, with the i500 showing better accuracy than the EZIS PO (P < 0.001).
Conclusion: Supragingival finish lines or the use of gingival displacement cords is recommended for clinically acceptable accuracy (< 100 µm) of the marginal region captured with an IOS.