Purpose. 3D printers are a new technology in dentistry. The purpose of this in-vitro study was to compare the mechanical properties of interim restorative materials produced using stereolithography (SLA), digital light processing (DLP), and liquid crystal display (LCD) technologies with the specimens produced by milling and conventionally manufactured polymethylmethacrylate (PMMA). Materials and Methods. Six different 3D-printers [2 brands for each of SLA (Formlabs and DWS), DLP (Asiga and Mega), and LCD (Vega and Photon) technologies] were used as experimental groups, and milling (Tempo-Cad; Ondent) and conventional (autopolymerizing PMMA, Imident; Imicryl) methods were used as controls. According to International Standards Organization (ISO) 10477:2004, 120 rectangular prism interim resin specimens with dimensions of 25×2×2 mm were prepared. The manufactured specimens were subjected to 3-point bending and micro-hardness tests. A Weibull analysis was performed. Fracture surface analysis was performed using SEM (FEI Quanta 650). Statistical data analysis was performed with a one-way ANOVA and a post hoc Dunnett T3 test (α =.05). Results. The mean flexural strength value of the milling group was statistically significantly higher than all other groups (P<.05) except the Formlabs group (P = 1.000). The mean elastic modulus values of DWS, Formlabs, Asiga, Vega, and conventional groups were not statistically significantly different from the milling group. All 3D-printer groups, except Photon, showed a statistically significantly higher microhardness value than the conventional group. Conclusion. All the interim resin materials produced with 6 different 3D-printers constituted a good alternative to the conventional method. However, only resin material produced with Formlabs showed similar mechanical properties to the milling method.
