Accuracy of Digital Impressions at Varying Implant Depths: An In Vitro Study

Purpose Implants placed at variable depths may vary the amount of visible scannable surface of a scan body. Intraoral scanner technology uses advanced optical principles to record the surface of the scan body to accurately capture the implant position. The purpose of this study is to investigate the effect implant placement depth has on the accuracy of digital implant impressions using an intraoral scanner. Materials and methods A partially edentulous gypsum master model was fabricated to allow the positioning of a single implant analog at different depths. Four groups were created based on the planned implant depths of 7, 6, 3, and 0 mm and corresponding visibility of the scan body at 2, 3, 6, and 9 mm. The model was digitized with a laboratory scanner for the reference scan and with an intraoral scanner to generate 15 test scans per group, with a total of 60 scans. The test scans were superimposed onto the reference scan using the best fit algorithm to analyze and measure the positional (dXYZ) and angular deviation (d ⍬) of the scan body using three-dimensional metrology software. Statistical analysis was performed using a one-way ANOVA and pairwise comparison was done with a Tukey-Kramer HSD test (alpha = 0.05). Results The one-way ANOVA of the groups for the dXYZ and d theta parameters was statistically significant (F-3,F-56 = 11.45, p < 0.001, F-3,F-56 = 24.04, p < 0.001). Group D (9 mm) showed the least positional deviation at 38.41 mu m (95% CI 30.26; 46.56) and the least angular deviation of 0.17 degrees (95% CI 0.12; 0.21). Group A (2 mm) showed the greatest positional deviation of 77.17 mu m (95% CI 65.23; 89.11) and greatest angular deviation of 0.84 degrees (95% CI 0.65; 1.03). The positional and angular deviation increased with increased implant depth. Conclusions The accuracy of digital impressions is influenced by the implant depth and the amount of visibility of the scan body. The trueness and precision are highest when the implant is placed at 0 mm depth with complete visibility of the scan body and decreases with subgingival implant placement.