Abstract:

Objective Cone beam computed tomography（CBCT）technology was used to measure the inclination angle of mandibular molars before and after orthodontic treatment of Angle Class Ⅰand skeletal class malocclusion，in order to obtain the ideal range of inclination angle of mandibular molars after orthodontic treat⁃ ment of malocclusion patients，improve the curative effect. Methods The CBCT scanning data of 28 patients with angle classⅠand skeletal classⅠmalocclusion were screened，and the images were corrected，reconstructed and measured. The mesial and distal inclination angles of mandibular molars were measured and statistically analyzed. Results The initial inclination angles of the mandibular first molar and mandibular second molar before orthodontic treatment were（13.9 ± 6.07）° and（19.0 ± 7.64）°，and the postoperative inclination angles of the mandibular first molar and mandibular second molar were（10.8 ± 6.07）° and（15.0 ± 8.38）° respectively. There is a statistical differ⁃ ence between the inclination angles of the mandibular first molar and second molar before and after treatment. There was no statistical difference in the initial inclination angle of mandibular molar inclination between adults and juveniles and also no statistical difference between patients with different mandibular plane angle patterns. Conclusion CBCT can directly，conveniently and accurately measure the axial inclination of mandibular molars， and obtain the ideal axial inclination range of mandibular first and second molars which is necessary for orthodontics.

Key words:

angle classⅠmalocclusion, skeletal classⅠmalocclusion, individual normal occlusion, mandibular molar, inclination angle, CBCT