Current Clear Aligners Under Scrutiny: Balancing the treatment alternatives choice and tissue loss

Background Numerous studies and applications are aimed at preventing tissue loss and tooth control in severe cases, but there has yet to be a large-scale sample analysis of the current clinical outcomes of clear aligner therapy (CAT). The aim of this retrospective study is to conduct the overall evaluation of alveolar bone and tooth root dimension changes in anterior teeth among different tooth extraction cases undergoing CAT, and provide available information for clinical guidance use in CAT. Methods 281 patients (186 non-extraction [NE] patients, 59 patients with two-premolar-extraction [TPE] in both maxilla and mandible and 36 patients with TPE in maxilla and one-lower-incisor-extraction [OLIE] in mandible) were selected from the records in recent 3 years. The dentoalveolar quantitative changes were analyzed using pre- (T1) and post-treatment (T2) computed tomography (CBCT). The measured parameters included alveolar bone height (ABH), alveolar bone thickness (ABT), and root length in anterior teeth among different tooth extraction cases. Results Alveolar bone height loss is common in all groups after CAT. Compared with NEs, TPE patients showed more risk of lingual bone dehiscence and torque loss (P < 0.05), while OLIE groups showed more risk of open gingival embrasures (OGE) (P < 0.05). More severe loss in mandibular anterior teeth were found compared to maxillary anterior teeth (P < 0.05). Conclusion Different tooth extraction types could lead to different degrees of bone loss along the direction of tooth movement, and orthodontists should adopt more cautious measures in mandibular anterior teeth. Even with numerous experimental studies for improving techniques and design in CAT, tooth control and complication prevention in extraction cases are still challenging for orthodontists.