Impact of different post-polymerization protocols on fracture load and two-body wear of 3D-printed fixed dental prostheses

Objectives To evaluate five post-polymerization protocols (385, 400 and 460 nm LEDs; one- and two-capacitor flashlights) and aging on fracture load (FL) and two-body wear (TBW) of three 3D-printed resins for fixed dental prostheses (FDPs). Materials and methods 360 single-unit FDPs for mandibular molars were DLP-printed from two permanent resins (Varseo Smile CrownPlus [VAR], Crowntec [CRO]) and one temporary resin (Freeprint temp [FRE]). Half was artificially aged (480,000 mastication cycles, thermocycling 5/55°C). FL was measured in a universal testing machine, TBW by laser scanning. Data were analysed with three-way ANOVA, Kruskal–Wallis and post-hoc tests (α = 0.05). Results The protocol ( p < 0.001) and the material ( p < 0.001) significantly affected FL, whereas aging showed no significant main effect ( p = 0.100); the three-way interaction was significant ( p = 0.009). Initially, 460 nm yielded the highest FL for VAR (1505 ± 251 N) and FRE (1910 ± 237 N), the two-capacitor flashlight for CRO (1783 ± 333 N). Aging increased FL significantly in two and decreased it in three of 15 combinations. TBW (− 0.16 to − 0.35 mm) did not differ between protocols or materials. Conclusions The protocol effect on FL depended on the material and the aging level. Aging had no overall effect but increased FL in two combinations, possibly through continued polymerization. Protocol selection should consider the material. Clinical relevance Mean fracture loads exceeded reported maximum molar bite forces, although individual specimens failed below that range. Two-capacitor flashlight post-curing gave the most consistent performance for the materials tested.