Comparison of subgingival finish line reproduction in intraoral scanning versus conventional impressions: a randomized crossover clinical study with/without gingival retraction

This is the authors' abstract. We don't add key points for this paper.

PURPOSE: To evaluate the competence of intraoral scanners in recording subgingival finish lines compared with conventional impressions, with and without gingival retraction. MATERIALS AND METHODS: A randomized crossover, clinical trial was conducted on 15 participants. Mandibular first molars were prepared for full-coverage crowns, and four impression techniques were performed: digital without retraction (DWR), digital with retraction (DR), conventional without retraction (CWR), and conventional with retraction (CR). A 1-week washout separated digital and conventional methods. STL files were generated and superimposed using a best-fit algorithm. Measurements were made at three sites (B-buccal, M-mesial, D-distal) for finish line width(1), depth(2), and gingival retraction(3). RESULTS: Significant intergroup differences were noted in B3, M1, M3, and D3. In these subgroups, DWR consistently demonstrated lower reproducibility. In B3, DR and CR were significantly better than DWR. In M1 and D3, DR, CWR, and CR showed significantly superior reproduction compared to DWR. In M3, CR showed significantly better results than DWR. Other parameters were comparable across groups. CONCLUSION: Digital and conventional impressions demonstrated higher reproducibility for shallow subgingival finish lines when gingival retraction was done. Without gingival retraction, finish line reproduced by conventional impressions was more defined than digital, underscoring the importance of retraction for reliable digital capture of subgingival margins.