Objectives: This study aimed to compare the fit accuracy between retainers fabricated using conventional cold-curing resin (hereinafter referred to as “conventional retainers”) and those fabricated using three-dimensional (3D) printing based on computer-aided design/computer-aided manufacturing (CAD/CAM) technology (hereinafter referred to as “CAD/CAM retainers”). Furthermore, the study aimed to compare two different methods to evaluate the fit accuracy: the impression replica technique and the 3D triple-scan protocol. Methods: For each of the 20 working models derived from a maxillary typodont, one conventional retainer and one CAD/CAM retainer were fabricated. The fit accuracy was evaluated using the impression replica technique and the 3D triple-scan protocol. Measurements were taken at 12 points on each model, and the differences in thickness (gap) were analyzed using Wilcoxon’s signed-rank test. Moreover, the correlation between thickness and measurement site was evaluated using Spearman’s rank correlation coefficient. Results: In both evaluation methods, the CAD/CAM retainers exhibited superior fit accuracy compared to the conventional retainers. Notably, the 3D triple-scan protocol clearly demonstrated that the fit accuracy differed depending on the measurement site. Conclusions: CAD/CAM retainers demonstrated superior fit accuracy compared to conventional retainers, possibly because digital design can account for polymerization shrinkage. In the impression replica technique, the median (interquartile range) thickness for the conventional retainers was 0.169 (0.120–0.260) mm, whereas that for the CAD/CAM retainers was 0.136 (0.096–0.198) mm. The CAD/CAM retainers showed significantly smaller gap values (p < 0.001). Within the limitations of this in vitro study, CAD/CAM retainers showed significantly smaller gap values than conventional retainers, indicating improved fit accuracy. In particular, the 3D triple-scan protocol accurately captured site-specific variations in fit accuracy among the anterior, canine, and molar regions.

Background/Objectives: Acceleration of orthodontic tooth movement remains a major challenge in clinical orthodontics. Evidence suggests that increased local blood flow around the alveolar bone is key to bone remodeling and potentially reflects early biological responses associated with accelerated orthodontics. This study aimed to investigate the effects of non-invasive physical stimuli on gingival microcirculation. Methods: Eight healthy adult male volunteers were included in the analysis. Gingival blood flow was assessed using laser Doppler flowmetry under the following conditions: no-stimulation condition (None) and four types of stimuli: thermal stimulation (THM), electric field stimulation (ELF), vibration stimulation (VIB), and far-infrared stimulation (FIR). Gingival blood flow was recorded before and after each stimulation, and the rate of change was calculated. Statistical analysis was performed using a linear mixed-effects model with Type III ANOVA (Satterthwaite approximation), followed by Dunnett-adjusted comparisons. Results: A statistically significant difference was observed between stimulation conditions (p = 0.0087). VIB significantly increased gingival blood flow compared with the no-stimulation condition (p = 0.0041), whereas ELF showed a trend toward increased blood flow (p = 0.0936); THM and FIR showed no statistically significant effects. Conclusions: The findings of this study suggest that non-invasive physical stimuli, particularly vibration stimulation, can enhance gingival microcirculation. Although tooth movement was not directly evaluated, the observed hemodynamic changes may represent short-term physiological responses to non-invasive physical stimulation.