Abstract
This study evaluated and compared nano-mechanical properties of three-dimensional printed epoxy based photopolymer and conventional autopolymerized acrylic resin. The effects of observation of printing layers (parallel vs. perpendicular to the layer) and water storage on the nano-mechanical properties were studied. Three different groups of specimens measuring (2.0 x 2.0 x 25.0) mm(3) were fabricated. Group 1 (n = 10) specimens were fabricated with horizontal printing direction and group 2 (n = 10) specimens were fabricated with vertical printing direction by additive manufacturing technology. Group 3 specimens were fabricated using conventional PMMA based autopolymerizing resin. The nano-mechanical properties were measured perpendicular and parallel to the printing layers using nano-indenter before and after water storage. The surface structure of representative experimental specimens were analyzed using scanning electron microscope with emphasis to the printing layer interface. Two-way ANOVA (Analysis of Variance) was used to compare the mean values before and after water storage at a significance level of p < 0.05. Highest values of the nano-mechanical properties were found by indentations perpendicular to the printing layer (Young's modulus: 3.739 +/- 0.233 GPa; nano-hardness: 0.180 +/- 0.022 GPa). The 3D printed specimens had higher nano-hardness and Young's modulus than conventional autopolymerized acrylic resin even after being stored in water for two weeks.