Effects of build direction on the mechanical properties of 3D-printed complete coverage interim dental restorations

Statement of problem. The application of 3-dimensional printing technology is emerging in dentistry and is being increasingly used to fabricate dental restorations. To date, scientific evidence is lacking regarding the effect of different factors on the mechanical properties of the printed restorations with the additive manufacturing technique. Purpose. The purpose of this in vitro study was to evaluate the effect of build direction (layer orientation) on the mechanical properties of a novel 3-dimensionally (3D)-printed dental restorative material. Material and methods. Based on the printing direction, 2 groups were tested. In the first group (n=20), the specimens were vertically printed with the layers oriented perpendicular to the load direction. In the second group (n=20), the specimens were horizontally printed with the layers oriented parallel to the load direction. All specimens were fabricated using the DW028D 3D-printer. The specimens were loaded with a universal testing machine at a crosshead speed of 1 mm/min with a 10-kN load cell. The test was performed at room temperature (22 degrees C) under dry testing conditions. The compressive strength was calculated for both groups, and the results were compared using the unpaired t test (alpha=.05). Results. The mean SD compressive strength for the vertically printed specimens was 297 MPa (+/- 34) compared with 257 MPa (+/- 41) for the horizontally printed specimens (P=.002). Conclusions. Within the limitations of this study, the layer orientation was found to influence the compressive strength of the material. Vertically printed specimens with the layers oriented perpendicular to load direction have improved mechanical properties more than horizontally printed specimens with the layers oriented parallel to load direction.