Cone-beam computed tomography evaluation of the distance between the root apex of mandibular molars and the inferior alveolar nerve canal in adults

To evaluate the spatiotemporal relationship between the root apex of mandibular molars and the inferior alveolar nerve canal (IANC) in adults.

Cone-beam computed tomography (CBCT) images were collected in 236 patients, and the distances from the root apexes of mandibular molars to the IANC were measured in NNT 4.6 software. The relationship between distance and gender was evaluated.

In two-rooted mandibular first molars, the distances from the mesial root and distal root to the IANC were 7.34 ± 2.07 mm and 6.69 ± 2.08 mm, respectively, in males and 6.47 ± 2.22 mm and 5.94 ± 2.11 mm in females. In three-rooted mandibular first molars, the distances from the mesial root, distobuccal root, and distolingual to the IANC were 7.29 ± 1.30 mm, 7.40 ± 2.33 mm, and 9.97 ± 2.19 mm, respectively, in males and 6.08 ± 2.57 mm, 6.35 ± 2.40 mm, and 9.01 ± 2.90 mm, respectively, in females. In one-rooted mandibular second molars, the distance from the root to the IANC was 4.09 ± 1.64 mm in males and 3.89 ± 1.76 mm in females. In two-rooted mandibular second molars, the distances from the mesial root and distal root to the IANC were 5.14 ± 2.08 mm and 4.39 ± 1.85 mm, respectively, in males and 3.78 ± 1.69 mm and 3.24 ± 1.72 mm, respectively, in females. There were no significant with in-gender differences between the left and right side in the distances from the root apexes to the IANC (P>0.05). The distances from the mandibular first molar were greater in males than in females. The longest average distance was from the distolingual root apexes of three-rooted mandibular first molars to the IANC, and the distances were longer from the distobuccal root apexes of three-rooted mandibular first molars to the IANC than from the distal root apexes of two-rooted mandibular first molars to the IANC (P<0.05). There was no within-gender difference in the distances from the root apexes of single-rooted mandibular second molars to the IANC (P>0.05), but the distances in two-rooted mandibular second molars were larger in males than in females (P<0.05). The distances from the root apexes to the IANC were smaller in mandibular second molars than in mandibular first molars (P<0.05).

There are significant differences between adult males and females in the distance from the root apex to the IANC for mandibular first molars and two-rooted mandibular second molars. The distances from the root apexes to the IANC were smaller in mandibular second molars than in mandibular first molars.