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

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.

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).

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.

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.