Three-dimensional evaluation of orthodontic treatment efficacy in patients with mild skeletal Class III malocclusion using clear aligners: a retrospective study

Abstract

Abstract Background This study aimed to retrospectively evaluate the treatment efficacy of clear aligners for individuals with mild skeletal Class III malocclusion. Methods A total of 35 patients with non-surgical Class III malocclusion that was treated by clear aligner technology (CAT) underwent analysis using the peer assessment rating (PAR) index, digital model analysis, and X-ray cephalometry. The PAR index was evaluated using plaster casts made before treatment (T0) and at the end of treatment (T1). Using 3DSMax software, a digital model of STL(Standard Template Library) scanned by intraoral scanners at T0 and T1 was reconstructed. Subsequently, an analysis was conducted to compare the distal movement of molars, arch width, and vertical height in three dimensions. X-ray cephalometry analysis was employed to evaluate alterations in the anterior tooth axis and mandibular plane. The significance level was established at P < 0.05. Results Throughout the treatment, the PAR index demonstrated a significant reduction in sagittal variation during the T1 phase, decreasing from 1.85 ± 1.064 to 0.07 ± 0.267. Additionally, the presence of anterior crossbite decreased from 3.33 ± 1.109 to 0.00 ± 0.000, suggesting a complete correction of the anterior crossbite. Digital model analysis indicated that the distal movement of the mandibular molars ranged from 1.7 to 2.0 mm. Additionally, the width of the dental arch in the mandibular premolar area exhibited a significant increase from 32.33 mm to 33.76 mm post-treatment. The SNB (°) decreased from 82.16 ± 3.91 to 80.89 ± 2.41, while the ANB (°) significantly increased from − 1.25 ± 2.12 to -0.07 ± 2.48. The MP-SN plane angle remained relatively stable, changing from 31.50 ± 9.77 to 31.83 ± 5.79 in X-ray cephalometric analysis. Conclusions CAT can effectively address non-surgical Class III malocclusion. In the sagittal plane, CAT can achieve an average of 1.7–2.0 mm distal movement of mandibular molars and demonstrates effective control in both horizontal and vertical directions.