Fracture Resistance of Artificially Aged Three-Unit Interim Fixed Dental Prostheses: A Comparison of an Additively Manufactured Photopolymer, a Milled PMMA, and a Conventionally Autopolymerized PEMA-Based Resin.

Interim fixed dental prostheses (FDPs) must withstand functional loading, thermal fluctuation, and moisture, yet comparative fracture resistance of additively manufactured, CAD/CAM-milled, and conventionally polymerized provisional materials after artificial aging remains unclear. Ninety three-unit interim FDPs (n = 30 per material) were fabricated from an additively manufactured photopolymer resin, CAD/CAM-milled poly(methyl methacrylate) (PMMA), or a conventionally autopolymerized powder-liquid poly(ethyl methacrylate) (PEMA)-based resin, and divided into non-aged and aged subgroups (5000 thermal cycles, 5/55 °C; n = 15). Restorations were seated without cementation on rigid titanium dies and loaded at the pontic to fracture (4 mm spherical indenter, 0.5 mm/min). The material-fabrication workflow grouping showed the largest effect on maximum fracture load (p < 0.001, η2p = 0.923): CAD/CAM-milled PMMA (1131.95 ± 135.31 N) > PEMA-based resin (475.06 ± 171.96 N) > photopolymer resin (163.34 ± 36.79 N). A material × aging interaction (p = 0.009) indicated that thermocycling reduced fracture load only in milled PMMA. For time to maximum load, only the interaction was significant (p = 0.008), driven by the photopolymer group. Fracture location and pattern varied by group. Within the limitations of this in vitro study, differences in maximum fracture load were primarily associated with the investigated material-fabrication workflow combinations, whereas aging effects were material-dependent.