Comparison between basal arch width in normal occlusions and class Ⅱ malocclusions by using cone-beam computed tomography

The purpose of this research was to investigate the measurements of maxillary and mandibular basal arch width in male and female with normal occlusion, and to compare dental arch width difference between normal occlusion and ClassⅡ malocclusion groups could be helpful in orthodontic diagnosis and treatment planning.Cone-beam computed tomography (CBCT) images from 133 individuals (76 males and 57 females) with normal occlusion and 64 (25 males and 39 females) with skeletal Class II malocclusions were evaluated. The distances between canines, first molars (basal arch widths: BAW) and second molars were measured from CRs (center of resistance) of the teeth and the projection of first molars on buccal bones (WALA distance) were measured.There were significant differences in male and female maxillary and mandibular dental transverse widths. The normal range of the maxilla and mandible basal bone widths differences were -2 mm-2 mm (-0.05 ± 2.17 mm). The normal occlusion and Class Ⅱ groups exhibited significant differences in the width of the intercanine and first molars. Sella-nasion-A point angle (SNA) and Sella-nasion-B point angle (SNB) in the Class Ⅱ male group were positively correlated with the width between the maxillary canines. For individuals with normal occlusions, the width of the mandible at the second molar was greater than that of the maxilla, so more attention should be paid to the width of the second molar when considering clinical treatment.Measuring the width of the maxilla and mandible basal bones from the resistance center of the first molar was a feasible and repeatable method can be used in clinical practice. The data could serve as a reference for orthodontic treatment planning. More consideration should be paid to the horizontal dental problems of the treatment plan for Class Ⅱ patients. And the width of the mandible at the second molar was greater than that of the maxilla, so more attention should be paid during treatment.