Bimaxillary dentoalveolar protrusion associates with labially angulated mandibular canine and mesial inclined mandibular first premolars—Based on CBCT image measurements

Background Bimaxillary dentoalveolar protrusion is a frequent complain in orthodontic clinic. The incisor angulation and inclination have been largely discussed. The present purpose was to assess the involvement of the teeth distal to incisors. Methods In this cross-sectional study, 63 patients with Class I occlusion and an average sagittal relationship between the maxilla and mandible were enrolled. Twenty-two cases (20.14 ± 7.32 years old) who had protrusion profile and flaring upper and lower incisors were diagnosed as bimaxillary dentoalveolar protrusion. The other 41 cases (21.87 ± 7.15 years old) who had a balanced facial profile and mild anterior crowding were taken as controls. The buccolingual angulation and the mesiodistal inclination of the canines and premolars, which had single root, revealed on the cone-beam computed tomography (CBCT) images were measured. The values of the angulation and inclination were compared between the two groups by using Student t-test methods (α = 0.05). Results The bilateral mandibular canines were more labially angulated (P＜0.001) but the bilateral mandibular first premolars were more mesial inclined in the bimaxillary dentoalveolar protrusion group than that in the control group (for tooth 34,P < 0.002; for tooth 44, P < 0.010). Conclusions More labial angulated mandibular canine and more mesial inclined mandibular first premolars associate with bimaxillary dentoalveolar protrusion. The labial-lingual angulation of the mandibular canines and the mesial-distal inclination of the mandibular first premolar should be paid a specially attention during the development, thus, the early intervention of the bimaxillary dentoalveolar protrusion.