デジタル精度 vs. 視覚的認識：口腔内スキャナーと従来のシェードガイドを使用したシェード選択信頼性の比較評価

Introduction Shade selection remains a critical yet challenging aspect of restorative and esthetic dentistry, particularly in the anterior region, where even minor discrepancies can compromise outcomes and patient satisfaction. This study aimed to evaluate the intra-method repeatability and inter-method agreement of shade selection using the conventional Vita Classical shade guide (Vita Zahnfabrik, Bad Säckingen, Germany) versus the 3Shape Trios 4 intraoral scanner (3Shape A/S, Copenhagen, Denmark) in a clinical setting. Materials and methods A prospective within-subject comparative study was conducted on 40 dental students aged 20-30 years with healthy unrestored maxillary central incisors. Each participant underwent shade assessment of both central incisors using both methods in three separate sessions under standardized illumination in a color-controlled operatory. Visual selection was performed by a calibrated prosthodontist using the Vita Classical guide, while digital analysis was carried out using the 3Shape Trios 4 scanner with factory-calibrated software. The teeth were cleaned and isolated prior to measurements, and the procedures were sequenced by blinding between methods. Data were recorded electronically and analyzed for reliability using appropriate statistical tests. Results The intra-method repeatability was significantly higher with the digital scanner (Fleiss κ = 0.83, p = 0.001) than with the visual guide (Fleiss κ = 0.25, p = 0.001). Inter-method agreement across all sessions was negligible (Cohen's κ = 0.03-0.05, p > 0.05), with 95% confidence intervals. Conclusion The 3Shape Trios 4 intraoral scanner provided highly reproducible shade data; however, the results differed substantially from those of conventional visual matching. These methods are not interchangeable. A combined approach using digital tools for consistency and visual assessment for clinical correlation is recommended to enhance the accuracy and predictability of esthetic restorations.