Marginal and internal fit of 3D printed permanent crowns: effect of CAD/CAM software, preparation type and resin material

With the advancement of digital technology, the stages of fabrication of temporary or permanent restorations with additive manufacturing (AM) are likely to become a routine in clinical dentistry. Compatibility with the teeth and surrounding gingival tissues is crucial for eliminating biological complications. Marginal and internal fit play a critical role in the mechanical continuity of the restoration and proper seating of the crown. The aim of the study is to evaluate the effects of CAD software, resin material and tooth preparation design on the marginal and internal fit of 3D printed resin nanohybrid crowns. Three typodont teeth were prepared with knife-edge, chamfer, and shoulder finishing lines. Crowns were designed using two CAD/CAM software systems (Exocad and 3Shape) and fabricated from two nanohybrid resin materials (VarseoSmile TriniQ and Saremco Crowntec). Marginal and internal fit were evaluated using the silicone replica technique (SRT) under ×40 magnification. Internal gaps were assessed separately for axial and occlusal regions. Data were analyzed using three-way ANOVA and Tukey post hoc tests (α = 0.05). Preparation design significantly affected marginal, axial internal and occlusal fit ( p < 0.05). Material type influenced marginal and axial internal fit ( p < 0.05), whereas CAD/CAM software affected only occlusal fit ( p < 0.05). Marginal gap values in all groups were within clinically acceptable limits. Axial internal gaps were generally within reported acceptable ranges, while occlusal gaps were consistently higher and, in several groups, approached or exceeded commonly accepted thresholds. Preparation design was the primary determinant of fit in 3D-printed resin crowns. While marginal and axial adaptation were clinically acceptable, occlusal internal discrepancies remain a critical limitation. Optimization of digital design parameters and preparation geometry is essential to improve the clinical performance of additively manufactured restorations.