Conventional Versus 3D-Printed Temporary Dental Crowns: A Micro-CT Analysis of Porosity and Fracture Resistance

Background: Temporary dental crowns are an essential component of fixed prosthodontic treatment, protecting prepared teeth and maintaining occlusal function and aesthetics until delivery of the definitive restoration. Their clinical performance is strongly influenced by their internal microstructure, which directly affects mechanical behavior. Therefore, the aim of this study was to compare the internal porosity and fracture resistance of temporary dental crowns fabricated using conventional and 3D-printing techniques. Materials and Methods: This in vitro study compared the porosity and fracture resistance of three materials for provisional restorations: a bis-acrylic resin (ProtempTM 4), an autopolymerizing resin (Success CD), and a 3D-printed light-curing resin (V-Print c&b temp). Thirty-six standardized single-unit crowns (n = 12 per group) were fabricated. All specimens were analyzed using high-resolution micro-computed tomography to determine total crown volume, pore volume, and relative porosity. Fracture resistance was evaluated under monotonic compressive loading in a universal testing machine. Data were analyzed using appropriate parametric or non-parametric statistical tests (α = 0.05). Results: The 3D-printed material exhibited the lowest mean porosity (0.0029%), whereas ProtempTM 4 and Success CD showed substantially higher porosity values. However, ProtempTM 4 demonstrated the highest mean fracture resistance, followed by the 3D-printed resin and Success CD. No direct correlation between porosity and fracture resistance was observed, indicating that material chemistry and internal bonding play a more decisive role than void content alone. Conclusions: These findings suggest that 3D printing improves structural homogeneity, while bis-acrylic materials provide superior load-bearing capacity, and that each fabrication method offers distinct advantages depending on clinical requirements.