Comparative Evaluation of Surface Adaptation and Mechanical Properties of Maxillary Complete Denture Bases Fabricated by Conventional and Three-Dimensional Printing Methods: A comparative in vitro study

Background Proper conformity of the denture base to the underlying mucosal tissues plays a fundamental role in ensuring the retention and stability of complete dentures. Although three-dimensional (3D) printing offers a more standardized manufacturing process than conventional compression molding, differences in surface adaptation and mechanical strength among fabrication techniques remain. The objective of this investigation was to evaluate and contrast the tissue surface adaptation and mechanical performance of maxillary complete denture bases produced through various fabrication techniques. Methods A gypsum cast derived from a prefabricated edentulous maxillary silicone mold was digitally scanned using an extraoral scanner, after which a denture base with a uniform thickness of 2 mm was designed in Exocad and saved in STL format. Denture bases were fabricated using digital light processing (DLP; Phrozen Lumi), liquid crystal display (LCD; Elegoo Saturn 4 Ultra 16K), and conventional compression molding (CM). For adaptation analysis, specimens were sectioned along transverse (maxillary second molar level) and sagittal (midline) planes, and the denture base–model gap was measured at six predefined ridge and palatal reference points using a stereomicroscope (20× magnification, 1 µm resolution). For mechanical evaluation, bar-shaped specimens (64 × 10 × 3.3 mm; n = 10 per group) were prepared according to ISO 20795-1:2013 and tested using a three-point flexural strength test on a universal testing machine (Instron). Results Regarding denture base adaptation, the compression molding (CM) group showed significantly better adaptation in the midpalatal region (B) than the LCD group. At the left ridge crest (C), the DLP group demonstrated superior adaptation compared with both the LCD and CM groups, while at the anterior ridge crest (D), the CM and DLP groups outperformed the LCD group. At the most posterior sagittal point (F), the CM group exhibited significantly better adaptation than both additively manufactured groups. Flexural strength differed significantly among groups, with the highest values observed in the CM group (153.88 ± 35.38 MPa). Among the additively manufactured groups, the LCD group (73.09 ± 2.23 MPa) showed higher flexural strength than the DLP group (66.93 ± 2.29 MPa). Conclusions The manufacturing technique significantly affects maxillary denture base adaptation in a region-dependent manner. Compression molding provided more favorable adaptation in the posterior palatal region, whereas DLP showed better adaptation than LCD. Conventionally heat-polymerized PMMA exhibited the highest flexural strength, while both 3D-printed groups met the ISO 20795-1:2013 minimum requirements. Therefore, fabrication technique selection should consider both the target adaptation region and mechanical performance requirements.