Marginal and internal fit accuracy of single-crown restorations: the impact of digital and conventional impression techniques

BACKGROUND: In this study, we aimed to compare the marginal and internal fit of single-crown restorations fabricated using digital and conventional impression techniques, and to evaluate the potential advantages of digital impressions over conventional polyvinyl siloxane-based methods. MATERIALS AND METHODS: A total of 120 extracted maxillary first molars were randomly assigned to two groups (n = 60 each): the conventional impression group (polyvinyl siloxane) and the digital impression group (TRIOS 3 intraoral scanner, 3Shape A/S, Copenhagen, Denmark). Standardized tooth preparations and CAD/CAM fabrication (IPS e.max CAD, Ivoclar Vivadent AG, Schaan, Liechtenstein) were performed for all samples. Marginal and internal fit were assessed using both the silicone replica technique and micro-computed tomography (micro-CT). Measurements were analyzed using independent samples t-tests. Intraobserver and interobserver reliability were evaluated using intraclass correlation coefficients (ICC). RESULTS: The digital impression group demonstrated significantly smaller marginal and internal gaps compared to the conventional group in both evaluation methods. In silicone replica analysis, marginal gaps were 45.8 ± 6.7 μm (digital) and 61.3 ± 7.5 μm (conventional) (p < 0.001); internal gaps were 84.5 ± 10.8 μm (digital) and 102.7 ± 12.1 μm (conventional) (p < 0.001). Micro-CT analysis confirmed these findings with marginal gaps of 43.2 ± 5.9 μm (digital) and 59.8 ± 6.4 μm (conventional) (p < 0.001), and internal gaps of 81.3 ± 9.6 μm (digital) and 98.4 ± 11.3 μm (conventional) (p < 0.001). Intraobserver and interobserver ICC values exceeded 0.95, indicating excellent measurement reliability. CONCLUSIONS: Digital impression techniques provided significantly superior marginal and internal adaptation compared to conventional polyvinyl siloxane-based impressions for single-crown restorations. The improved accuracy, combined with workflow efficiency and patient comfort, supports the clinical adoption of digital impression systems.