Volumetric and tridimensional root resorption and alveolar bone changes in Class II malocclusion extraction protocol treated with clear aligners and fixed orthodontic appliances: A comparative study

Abstract

Introduction This study aimed to assess the root resorption and alveolar bone changes of maxillary incisors volumetrically and 3-dimensionally in patients with Class II Division 1 malocclusion who underwent treatments involving the extraction of 4 first premolars with conventional fixed appliances (FAs) vs clear aligners (CAs). Methods A total of 320 maxillary incisors from 80 patients were assessed and divided into 2 groups (FAs and CAs), each possessing similar baseline characteristics. Pretreatment and posttreatment cone-beam computed tomography scans were used to analyze linear and volumetric orthodontically induced inflammatory root resorption, alveolar bone thickness (ABT), alveolar bone height (ABH), as well as anteroposterior and vertical movements of maxillary incisors. Results Both groups revealed a significant reduction in palatal ABT and an increase in labial ABT in both the central and lateral incisors. The total ABT reduction was more pronounced in the FAs group than in the CAs group (P <0.005). In terms of ABH, FAs treatment resulted in more labial and palatal marginal alveolar bone resorption around the maxillary incisors. The root length and volume losses in the CAs group were significantly less than those in the FAs group: 0.90 ± 0.97 vs 1.85 ± 1.18 mm and 19.59 ± 8.75 vs 24.28 ± 10.05 mm3, respectively. The axial inclination was significantly less in the CAs group than in the FAs group: 8.83 ± 8.73 vs 2.64 ± 12.31°. Conclusions Treatments of Class II Division 1 malocclusion with FAs and CAs appeared to cause a statistically significant palatal ABT reduction and maxillary incisors root resorptions, with the FAs treatment causing a more significant effect. Both treatment modalities significantly reduced the ABH, with the greatest reduction found on the lateral incisors’ palatal side in the FAs group. The CAs treatment resulted in a more significant incisor lingual tipping.