Assessment of the trueness of the tissue surface for 3D-printed and injection-molded mandibular complete denture base fabrication

As digital methods are widely used in clinical dentistry, the accuracy of dental prostheses remains critical. However, how each step in both conventional and digital methods affects the accuracy of the overall area and each area of the tissue surface remains unclear. This study aims to evaluate the effects of three-dimensional (3D) printing and injection molding processes on the trueness of mandibular complete denture bases. Ten physical impressions were made using a standard edentulous lower jaw plaster model. In accordance with the scan data from these impressions, the denture bases were designed and fabricated using 3D printing. Additionally, conventional polymethyl methacrylate (PMMA) denture bases were made from the same impressions via the injection molding method. The tissue surfaces were scanned and divided into four regions. Deviation analyses were performed using the root mean square (RMS) method. Two-way ANOVA was employed for statistical analyses. A significant difference in trueness was found between the two methods (p < 0.05). In the injection molding process, the largest deviation originated primarily from the plaster filling process (222.35 ± 11.77 μm), followed by wax-up fabrication (211.10 ± 55.25 μm) and resin injection (161.87 ± 59.95 μm). The deviation of the border seal area was the greatest among the regions. In the 3D printing process, the CAD design showed the greatest deviation (179.22 ± 55.13 μm). The maximum deviation was 219.83 ± 45.37 μm in the border seal area. The printing process was associated with a deviation of 138.10 ± 24.42 μm, with the maximum deviation in the retromolar pad area reaching 193.92 ± 28.13 μm. Both methods demonstrated clinically acceptable tissue surface adaptation. The 3D-printed base better adapted to the integrated tissue surface, especially in the border seal area. However, owing to the significant differences observed in this study, further clinical validation is needed.