Anatomical Features Of The Mandible In Patients With Molar Impaction

To investigate the anatomical features of the mandible in patients with mesio-impacted mandibular second molars (MM2) in three dimensions and provide a theoretical basis for predicting possible trends in mandibular development. 222 subjects who underwent cone-beam computed tomography (CBCT) were included and divided into three groups: unilaterally mesio-impacted MM2, bilaterally mesio-impacted MM2, and age- and sex-matched controls. 33 measurements were selected, consisting of 23 linear and 10 angular measurements. The study showed that the width of the crown of mandibular first molar (MM1), the length and width of the crown of MM2 were significantly higher in groups with impacted MM2, while the length and the height of the eruption space were lower in those groups. In addition, the length of the mandible body were lower in groups with impacted MM2, while the gnathion angle and mandibular angle were higher. There was positive correlation between mesio-impacted MM2 and the length, the width of MM2 crowns, the angle between MM2 and mandibular ramus (MR), but the length between MM1 and MR, and the length of eruption space of MM2 had negative effects. The sagittal eruptive space was insufficient for MM2, while the width of the mandibular arch was not affected. The length of mandibular body was smaller in patients with impacted MM2, while the gnathion angle and submandibular angle were larger, indicating the tendency of reduced length in the sagittal direction and high-angle malocclusion. Furthermore, sex was not associated with the impaction of MM2.