Build angle and its influence on the flexure strength of stereolithography printed hybrid resin material An in vitro study and a fractographic analysis

This study evaluated the effect of build direction on the flexure strength of stereolithography (SLA), 3D-printed hybrid composite resin material. A total of 26 bar-shaped specimens were 3D-printed using SLA-based printer. The specimens were divided into two groups based on build direction (n = 13); vertically (V), horizontally (H) printed groups. The layer thickness was 0·05 mm. Three-point bending test was performed using a universal testing machine, with a load-cell of 250 N at 1 mm min−1 crosshead speed until failure of the specimens. The fractured surfaces were analyzed using scanning electron microscopy (SEM). The mean flexure strength for (V) and (H) printed specimens was 88.2 and 90.5 MPa respectively (P > .05). Fractographic analysis revealed brittle abrupt fracture pattern for (V) group and a ductile, slow pattern with layer delamination for H-group. Though there was no statistical difference in flexure strength between the test groups, the fractographic analysis revealed that the fracture mode was different.