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Al Assadi, Faisal

University of British Columbia

Purpose: The aim of this study was to evaluate the influence of horizontal gingival displacement on the accuracy of an intraoral scanner (IOS) with 0.5 and 1mm subgingival finish lines. Materials and Methods: A 3D printed resin dental model was fabricated with a removable milled zirconia die of tooth #46 full crown preparation and 3D printed resin gingiva. A supragingival control group, and six test groups were designed and fabricated with varying horizontal gingival displacement (0.12mm, 0.25mm 0.45mm) each with subgingival finish line positions of 0.5mm (groups 1 to 3, respectively) and 1mm (groups 4 to 6, respectively). The Trios3 (3Shape) IOS was used to scan 18 samples per group and the scans were superimposed with a reference scan of the die without the gingiva. Absolute marginal discrepancies (AMD) between test and reference scans were measured at 8 fixed points around the prep, and at the largest marginal discrepancy (LMD) site. The one-way ANOVA test measured statistical differences between the groups, and the Games-Howell test compared each pair of groups. Results: The highest mean AMDs at fixed sites were on the distolingual surface for all study groups including the control group (p<0.001), but with inconsistent statistical differences between groups. Group 5 showed the highest mean AMD of 0.203mm followed by Group 4 at 0.194mm, while the control group showed 0.054mm, which was well below a clinically acceptable crown margin gap of 100μm. Mean LMDs were highest in Groups 1 and 4 (0.12mm displacement) with 0.913 and 1.130mm respectively, whereas the lowest values were in group 3 and 6 (0.45mm displacement) with 0.162 and 0.113mm, which were still higher than the control 0.065mm. Differences in LMDs between groups were all statistically significant (p<0.001) except between Groups 2 and 5, and Groups 3 and 6. Conclusion: Within the study limitations, the accuracy of an IOS is significantly reduced when capturing subgingival finish lines. Moreover, the amount of horizontal gingival displacement was shown to have a significant effect in improving the accuracy of digital impressions. A minimum horizontal gingival displacement of 0.25mm should be achieved by gingival retraction techniques to improve scanning quality.

Text

2023-09-07

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/85876

Craniofacial Science

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/