Fracture load of 3D-printed fixed dental prostheses compared with milled and conventionally fabricated ones: the impact of resin material, build direction, post-curing, and artificial aging-an in vitro study

Objective To investigate the impact of 3D print material, build direction, post-curing, and artificial aging on fracture load of fixed dental prostheses (FDPs). Materials and methods Three-unit FDPs were 3D-printed using experimental resin (EXP), NextDent C&B (CB), Freeprint temp (FT), and 3Delta temp (DT). In the first part, the impacts of build direction and artificial aging were tested. FDPs were manufactured with their long-axis positioned either occlusal, buccal, or distal to the printer's platform. Fracture load was measured after artificial aging (H2O: 21 days, 37 degrees C). In the second part, the impact of post-curing was tested. FDPs were post-cured using Labolight DUO, Otoflash G171, and LC-3DPrint Box. While the positive control group was milled from TelioCAD (TC), the negative control group was fabricated from a conventional interim material Luxatemp (LT). The measured initial fracture loads were compared with those after artificial aging. Each subgroup contained 15 specimens. Data were analyzed using Kolmogorov-Smirnov test, one-way ANOVA followed by Scheffe post hoc test, t test, Kruskal-Wallis test, and Mann-Whitney U test (p < 0.05). The univariate ANOVA with partial eta squared (eta(2)(P)) was used to analyze the impact of test parameters on fracture load. Results Specimens manufactured with their long-axis positioned distal to the printer's platform showed higher fracture load than occlusal ones (p = 0.049). The highest values were observed for CB, followed by DT (p < 0.001). EXP showed the lowest values, followed by FT (p < 0.001). After artificial aging, a decrease of fracture load for EXP (p < 0.001) and DT (p < 0.001) was observed. The highest impact on values was exerted by interactions between 3D print material and post-curing unit (eta(2)(P) = 0.233, p < 0.001), followed by the 3D print material (eta(2)(P) = 0.219, p < 0.001) and curing device (eta(2)(P) = 0.108, p < 0.001). Conclusions Build direction, post-curing, artificial aging, and material have an impact on the mechanical stability of printed FDPs.