Evaluation of the marginal fit and fracture resistance of interim restorations fabricated using different techniques: an in vitro study

Background Interim restorations are essential for preserving structural integrity and function until the definitive restoration is placed. Their mechanical properties and marginal fit are crucial for clinical performance and are influenced by the fabrication technique and material used. Aim The aim of this in vitro study was to investigate the marginal fit and fracture resistance of manually fabricated, computer-aided design and computer-aided manufacturing (CAD/CAM) milled, and CAD/CAM three-dimensionally (3D) printed 3-unit interim fixed dental prostheses (FDPs). Materials and methods Sixty-four 3-unit interim FDPs were fabricated on epoxy resin models using different fabrication techniques: manual fabrication with poly methyl methacrylate (PMMA) (n = 16), manual fabrication with Bis-acrylic composite resin (n = 16), CAD/CAM milling (n = 16), and CAD/CAM 3D-printing with a digital light processing (DLP) printer (n = 16). The vertical marginal fit of the interim FDPs was evaluated using a stereomicroscope. Following cementation, the specimens were subjected to cyclic loading and then tested for fracture resistance using a universal testing machine. Data were analyzed using one-way ANOVA, and Tukey's post hoc test was performed to identify statistical differences between the means of independent group pairs. Results The smallest marginal gap (31.77 +/- 9.0 mu m) was observed in the milling group, followed by the 3D-printing group, with no significant difference between the two (p = 0.98). Both groups demonstrated significantly smaller marginal gaps compared to the manual fabrication groups (p < 0.001). In terms of fracture resistance, the 3D-printing group showed the highest values (1244.46 +/- 290.04 N), followed by the milling group, with no significant difference between them (p = 0.32). Both groups exhibited significantly higher fracture resistance than the manual fabrication groups (p < 0.001). Conclusion CAD/CAM 3D-printed and milled interim FDPs demonstrated superior marginal fit and fracture resistance, making them more suitable than conventional techniques, particularly for multi-unit restorations or long-term applications.