Clinical Oral Investigations Comparison of localized mandible morphology between patients with impacted and non-impacted mandibular second molars in three dimensions

Abstract

Abstract Objectives To investigate the morphological differences of localized mandible between patients with impacted mandibular second molars (MM2) and non-impacted patients through mandibular measurements in three dimensions. Materials and methods The 222 subjects who underwent cone-beam computed tomography (CBCT) were included and divided into three groups. Group 1 (G1) comprised 64 patients with unilaterally impacted MM2, group 2 (G2) was composed of 54 patients with bilaterally impacted MM2, and group 3 (G3) was made up of 104 age- and sex-matched controls. 24 measurements were selected, including 21 linear measurements and 3 angular measurements. Results The width of mandibular first molar (MM1), the length and width of MM2, the angle between MM1 and MM2, the angle between MM2 and ascending mandibular ramus (MR) were higher in G1 and G2 than in G3 (P < 0.05). Also, the length of MM1 and MM2, the angle between MM1 and MM2 were statistically higher in the impacted side than in the non-impacted side for G1. There was positive correlation between impacted MM2 and the length, the width of MM2, the angle between MM2 and MR, but the length between MM1 and MR, the length of alveolar bone for eruption of MM2 had negative effects. Conclusions The crown of MM1 and MM2 were larger in the patient of impacted MM2. The eruption space of MM2 was insufficient, while the width of mandibular arch were not affected in impacted patients. Clinical Relevance Impacted mandibular second molars are more common in clinic.