3D Evaluation of material-dependent volumetric and interfacial changes in CAD/CAM partial crowns: a semi-automated micro-CT approach.

OBJECTIVES: Changes in the 3D volumes, interfaces, and interfacial gap formation were examined of adhesively luted lithium disilicate (LS2) and resin-based composite (RBC) partial crowns during artificial aging and imaged by micro-computed tomography (micro-CT). METHODS: Sixteen human mandibular molars were restored using either 8 CAD/CAM partial crowns made of LS2 (IPS e.max® CAD) or RBC (Tetric® CAD). After adhesive luting (Variolink® Esthetic DC, adhesive luting composite), artificial aging [water storage for 90 days (t1) and thermo-mechanical loading (t2)], the partial crowns were analyzed by micro-CT (Avizo, Biomedisa). Paired t-test, ANOVA and Tukey HSD test (α = 0.05) were used to analyze area and volume parameters; e.g., luting space volume (VLS), luting space thickness (TLS), and partial crown contact area to the cavity and tooth tissues (CPT). RESULTS: Across artificial aging, most area parameters and all four volume parameters remained stable in both materials. Yet, there were changing values in areas of direct contact between the partial crown material and the tooth tissues: CPE, CPT were generally smaller at t1 for LS2 (2.2 ± 1.2%) compared to RBC (4.5 ± 1.3%), especially at the inflection and saddle points of the round preparation form. Across both time points, LS2 showed consistently higher mean luting space thickness than RBC. It remained without gap progression. CONCLUSIONS: The semi-automated 3D micro-CT analysis enables a comprehensive evaluation of adhesive interfaces and may help to develop new ideas to enhance long-term restoration outcomes. RBC partial crowns had more surfaces in direct contact with the cavity floor than LS2 partial crowns. CLINICAL SIGNIFICANCE: The approach with Biomedisa has potential translational value and may enable individualized quality control and long-term monitoring of adhesive restorations in clinical practice. Both materials achieve comparable survival rates, wear resistance, and interface stability under simulated conditions and when minimum material thickness is respected.