BACKGROUND:Clinical evaluation gives much attention to occlusion and improvement of soft tissue profile,while little is reported concerning the stress distribution on the temporomandibular joint in the treatment of Class Ⅱ division 1 malocclusion adult patients undergoing single maxillary extraction orthodontics.OBJECTIVE:To analyze the stress distribution on the temporomandibular joint in the treatment of Class Ⅱ division 1 malocclusion with single maxillary extraction orthodontics.METHODS:The three-dimensional finite element models of normal and Class Ⅱ division 1 malocclusion before and after single maxillary extraction orthodontics according to CT and MRI data.The stress distribution on the temporomandibular joint was analyzed after mechanical loading and boundary constraint.RESULTS AND CONCLUSION:Compared with Class Ⅱ division 1 malocclusion,the stress distribution on the temporomandibular joint after single maxillary extraction orthodontics had no significant stress concentration area,and the equivalent stress of the condyle was lower than that before treatment,and the equivalent stress of the articular disc and the glenoid fossa of temporal bone were larger than those before treatment.However,the stress was well-distributed,basically fulfilling the stress characteristics of normal occlusion.To conclude,single maxillary extraction orthodontics reduces the risk of temporomandibular joint disorder in the patients with Class Ⅱ division 1 malocclusion,which is balanced and stable in line with the goal of orthodontic treatment.