Capturing of interdental areas with digital and conventional impression systems and their impact on automatic tooth segmentation in CAD software: an in vitro study

Abstract

This in vitro study evaluated and compared the accuracy of digital versus conventional impression systems in reproducing interdental areas (IAs) of periodontally compromised dentitions (PCDs) and examined how impression quality influences automated tooth segmentation in CAD software. A standardized PCD model was captured with one conventional polyvinylsiloxane impression (CVI), four wireless intra‑oral scanners (IOS) - Dexis IS 3800 W (3800‑wl), Medit i700w (i700‑wl), Primescan 2 (PRI2‑wl), Trios 5 (TRI5‑wl) - and a wired Primescan AC (PRI1‑w). Raw scan data, digitally mounted casts after scan‑repair, and digital casts after tooth segmentation in OnyxCeph were analyzed. IA reproduction accuracy and segmentation quality were statistically compared using the Median test and Chi‑squared test (p < 0.05). All IOS reproduced IAs significantly more accurately than the CVI (p < 0.001). Among IOS, PRI2‑wl achieved > 80% correct IA reproduction, whereas 3800‑wl and TRI5‑wl fell short by up to 20%. Scan‑repair marginally improved IA capture for some IOS, while the conventional impression showed no change. Segmentation errors clustered in teeth with pronounced gingival recession; healthy gingiva yielded higher accuracy. Significant differences between raw and segmented data were found for TRI5‑wl (p = 0.027) and 3800‑wl (p = 0.044). Within the limits of this in vitro study, IOS outperform conventional impressions for IA reproduction in PCDs. Accuracy varies among IOS and is linked to raw‑scan quality. Automated segmentation is reliable for teeth with healthy gingiva but is challenged by periodontal defects. Precise IA capture enhances orthodontic movement planning and streamlines CAD‑based workflows, reducing manual corrections and improving outcomes for patients with compromised periodontium.