Accuracy and clinical performance of conventional versus digital impressions for maxillary complete dentures: a randomized controlled clinical trial

This study aimed to compare the three-dimensional trueness of digital impressions with conventional impressions for maxillary complete dentures and to evaluate the clinical performance of denture bases fabricated from each technique. Twenty completely edentulous participants received both conventional impressions and digital impressions using an intraoral scanner in a randomized crossover design. Conventional impressions were digitized and used as reference models. Trueness was assessed by root mean square (RMS) deviations for the entire surface and predefined anatomical regions. Denture bases were fabricated using stereolithographic 3D printing. Retention, stability, and support were clinically evaluated by blinded examiners. Statistical analyses included parametric and nonparametric tests (α = 0.05) with effect size estimation. Mean RMS deviation for the entire digital impression was 234.63 ± 43.87 μm and was significantly below the 300-µm reference threshold (Cohen’s d = − 1.49, representing the standardized difference from this threshold). The palatal vault (d = − 3.03) and ridge crest (d = − 2.88) showed the largest standardized differences below the 300-µm threshold, whereas the peripheral border (d = 1.47) and posterior palatal seal (d = 0.85) showed standardized differences above the threshold ( P ≤ 0.001). Conventional denture bases showed significantly higher posterior retention, lateral and anteroposterior stability, and anteroposterior support ( r = 0.60–0.77; P ≤ 0.007). No significant differences were observed for anterior retention or lateral support. Digital impressions demonstrated region-dependent trueness relative to conventional reference impressions, with lower deviations in the palatal vault and ridge crest regions and greater deviations in peripheral and posterior sealing regions. However, conventional impressions provided superior clinical performance for several retention, stability, and support parameters.