Relationship between Root Apices and the Mandibular Canal: A Cone-beam Computed Tomographic Analysis in a German Population

• The purpose of this study was to assess the mean distance between the mandibular canal and the apices of the adjacent teeth.
• There is no other study available including such a large number of patients (N = 627) with a comparable number of teeth (N = 1974) and roots (N = 3127).
• The present investigation is the first study reporting a relatively high incidence of direct communication between the mandibular canal and the root apices of mandibular teeth.
• Females have a significantly shorter distance and more often show direct communication between root apices and the mandibular canal; therefore, they have a potentially higher risk of suffering nerve damage.
• The present study suggests that vertical growth of the mandible seems to be a continuous pattern and shows a maximum between 36 and 45 years of age.
• The present study reveals that cone-beam computed tomographic imaging provides exact distortion- and superimposition-free images of the relevant anatomic structures.

IntroductionThe purpose of this study was to assess the mean distance between the mandibular canal and the apices of the adjacent teeth.MethodsSix hundred twenty-seven full-size cone-beam computed tomographic radiographs (Planmeca Promax3D; Planmeca, Helsinki, Finland; volume 8 × 8cm, voxel size ≤0.2 mm) of a German population (female = 58.2%, male = 41.8%, mean age = 51 years) were analyzed to establish the shortest distance between the mandibular canal and the root apices of the second premolar and all molars using the multiplanar reconstruction of the manufacturer's software in 3 mutually orthogonal planes. The obtained metric data were statistically analyzed using Student-Neumann-Keuls and Scheffé tests. Concerning the position of the tooth, the left or right side, and the sex of the patients, the chi-square test was used.ResultsA total of 821 second mandibular premolars and 597 first, 508 second, and 48 third mandibular molars were included, and the mean distances were 4.2, 4.9, 3.1, and 2.6 mm, respectively. The occurrence of a direct relationship between the root tips and the mandibular canal was found in 3.2%, 2.9%, 15.2%, and 31.3% of the teeth. Women were almost twice as often affected as men. No significant differences were found concerning the location (right/left) of the teeth (P > .05). Significantly shorter distances from the mandibular canal to the root apices were found in patients younger than 35 years compared with older patients (P < .0012).ConclusionsDirect communication between the root apices and the mandibular canal is not rare and has to be taken into consideration when performing surgical or endodontic procedures to avoid iatrogenic nerve damages. Distances depend on sex and age.