Abstract
The best timing for treating adolescent patients with skeletal class III malocclusion is still unclear. The present study aimed to explore variations in the efficacy of rapid expansion combined with maxillary protraction therapy in patients with skeletal class III malocclusion at different growth and development stages. Clinical records of 45 patients with skeletal class III malocclusion who underwent rapid expansion combined with maxillary protraction therapy from January 2019 to June 2022 were included in the present study. Based on the cervical vertebral maturation method (CVM), the patients were retrospectively divided into three groups: Pre-pubertal (CVM stages I-II, n=15), pubertal (CVM stage III, n=15) and post-pubertal (CVM stages IV-VI, n=15). Lateral head radiographs before and after the treatment and various bone, dental and soft tissue measurements were compared between groups to assess the differences in treatment effects. The results of the intra-group comparison before and after the treatment showed that the dental and bone indicators, such as A Point-Nasion-Point B angle, sella-nasion-A point angle, sella-nasion-B point angle, mandibular plane angle, A Point-VR plane and anterior Nasal-VR plane (ANS-VR) were significantly different compared with those before treatment in all three groups of patients (P<0.05). The posterior Nasal-VR plane (PNS-VR) changed significantly in the pre-pubertal and pubertal groups (P<0.05), but there was no significant change in the post-pubertal group. The Glabella-Pronasale-Pogonion of soft tissue and Sella-Nasion-Nasion-Bs Point angle decreased significantly post-treatment in the three groups, while the Sella-Nasion-Nasion-Sn Point angle increased (P<0.05). Intergroup comparisons before and after treatment showed that there was no significant difference in the post-treatment indexes between the pre-pubertal and pubertal groups. The changes in ANS-VR and PNS-VR values before and after treatment were statistically significant between the post-pubertal and the other two groups (P<0.05). In conclusion, rapid expansion combined with maxillary protraction therapy has the best treatment effects in patients in the pre-pubertal and pubertal stages and is associated with significant skeletal effects and less alveolar response. Although the skeletal treatment effects are less favorable in patients in the post-pubertal stage with more pronounced alveolar responses, the treatment can still provide appropriate compensation for facial deformities and reduce the likelihood of orthognathic surgery.