Do bar supports affect the accuracy of mandibular complete denture bases produced with additive manufacturing at different printing orientations? An in vitro evaluation

Purpose: This in vitro study aimed to determine if the addition of bar supports influences the trueness or precision of additively manufactured mandibular complete denture bases. Methods: 100 denture bases were additively manufactured via digital light processing from a photopolymer acrylate at 0, 15, 45, 60, and 90° printing orientation. For each printing orientation cylindrical bar supports, with a diameter of 4 mm, were added on the denture base lingual to the second molars and perpendicular to the lingual midline then left off to investigate if this influenced the outcomes. The analysis was conducted on the intaglio surface of the denture base with a metrology software and the outcome being root mean square. The analysis was separated into three separate regions (anterior, middle, and posterior) to aid discussion and clinical interpretation. The results were analysed for descriptive statistics and differences analysed with a series of one-way ANOVA tests for the regions and Tukey test for multiple comparisons to a statistical significance of P < .05. A linear regression analysis was conducted to evaluate the affect of orientation, bar supports and the region on the overall trueness and precision levels. Results: The 15° printing orientation demonstrated the highest degree of accuracy (Mean RMS:6.76, SD 0.54) while 45° performed the worst (Mean RMS:10, SD: 0.45). A regression analysis determined that the support struts had a significant (P < .001) impact on accuracy for the different anatomical regions. Conclusion: The accuracy of mandibular complete denture bases, that are additively manufactured, can be improved by incorporating lower printing angulation and bar supports. Clinical significance: Lack of trueness and precision of the intaglio surface of a complete mandibular denture base may affect the stability and increase the need for post insert adjustment appointments. Care should be given when considering the printing orientation and the addition of bar supports for a complete mandibular denture base to minimise these clinical complications.