Effect of Different Print Orientations on the Flexural Strength of 3D Printed Denture Base Resin

Statement of problem. The introduction of additive manufacturing to the field of prosthodontics has recently made it possible to fabricate 3D printed complete dentures; however, there is limited data evaluating the flexural strength of 3D printed denture base resins and the effect of print orientation on flexural strength. Purpose. The purpose of this in vitro study was to evaluate the effect of print orientation on flexural strength of 3D-printed denture base resin and compare it to flexural strength of compression molded denture base resin. Materials and methods. Four groups (n=10) of denture base resins (64 mm × 10 mm × 3.3 mm) were fabricated; 10 compression molded as the control, 10 printed in a vertical orientation, 10 printed in 45˚ orientation, and 10 printed in a horizontal orientation. Specimens were stored in water for 1 week and then underwent a three-point bending test to measure flexural strength. Statistical analysis was performed using one-way analysis of variance (ANOVA) followed by the Tukey HSD post hoc test (α=.05). Results. Average values of flexural strength for the 3D printed and control group were 100.6 ± 13.5 MPa (vertical orientation), 81.9 ± 13.1 MPa (45˚ orientation), 73.9 ± 8.5 MPa (horizontal orientation), and 82.3 ± 11.1 MPa (compression molded). There was a statistically significant difference among groups as demonstrated by one-way ANOVA (P<.05). The post hoc Tukey HSD test indicated that flexural strength of the vertical 3D printed group was statistically higher than 45˚ 3D printed groups (P=.006), the horizontal 3D printed group (P=.000) and the compression molded group. (P=.007). The test also showed no significant difference between the 45˚and horizontal 3D printed groups (P=.430), the 45˚ 3D printed and compression molded groups (P=1.000), and the horizontal 3D printed and compression molded groups (P=.399). Conclusions. The vertical print orientation group produced the highest flexural strength in comparison to the 45˚ orientation group, the horizontal orientation group, and the compression molded group. Clinical implication. The obtained results suggest that optimal printing orientation for denture base resin is vertical and that 3D printed denture bases may be a useful alternative to conventionally processed denture bases