Fracture load of 3D printed fixed dental protheses

Objectives: The study investigated the impact of build direction, post-curing and artificial aging of different 3D print materials on fracture load (FL) of FDPs (fixed dental prostheses) for temporary use compared to milled and conventionally fabricated ones.
Methods: Monolithic three-unit FDPs were 3D printed using the following materials: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 on FL were tested. FDPs from each material were manufactured with their long-axis positioned either occlusal, buccal or distal to the printer’s platform. FL (1mm/min) was measured after artificial aging (H₂O: 21 days, 37°C). In the second part, the impact of post-curing on FL 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 temporary material Luxatemp [LT]. These initial FL values were compared to those after aging. Each subgroup contained 15 specimens. Data were analysed using Kolmogorov-Smirnov test, univariate ANOVA with partial eta squared (η_P²), one-way ANOVA followed by post-hoc Scheffé test, t-test, Kruskal-Wallis- and Mann Whitney U- test (p<0.05).
Results: Specimens manufactured with their long-axis positioned distal to the printer’s platformshowed higher FL than occlusal ones (p=0.049). The highest FL values were observed for CB, followed by DT (p<0.001). EXP showed the lowest FL, followed by FT (p<0.001).After artificial aging a decrease of FL for EXP (p<0.001) and DT (p<0.001) was observed. The highest impact on FL was exerted by interactions between 3D print material and post-curing unit (η_P²=0.233, p<0.001), followed by the 3D print material (η_P²=0.219, p<0.001) and curing device (η_P²=0.108, p<0.001).
Conclusions: Build direction and post-curing have an impact on the mechanical stability of 3D printed FDPs.