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. 2018 Jun;40(6):609-614.
doi: 10.1007/s00276-017-1928-6. Epub 2017 Oct 27.

Anatomic study of the position of the mandibular canal and corresponding mandibular third molar on cone-beam computed tomography images

Liqun Gu  1   2 , Chao Zhu  2 , Kejia Chen  3 , Xianchu Liu  3 , Zhangui Tang  4
Affiliations

Anatomic study of the position of the mandibular canal and corresponding mandibular third molar on cone-beam computed tomography images

Liqun Gu et al. Surg Radiol Anat. 2018 Jun.

Abstract

Purpose: The positional relationship between the mandibular canal and corresponding third molars is a key anatomic factor of inferior alveolar nerve (IAN) injury. The aim of the present study is to classify the anatomic three-dimensional relationship between the mandibular third molar and the mandibular canal on cone-beam computed tomography (CBCT) images.

Methods: This study used CBCT images to classify the positional relationship between the mandibular canal and corresponding third molars. CBCT images of 749 patients (1296 mandibular third molars) were analyzed to draw up a classification.

Results: On a total of 1296 third molars, the mandibular canal relative to the roots of the mandibular third molar was on the apical side (88.1%), followed by the buccal side (7.9%), the lingual side (3.5%), and then between the roots (0.5%). Ninety-five (7.1%) third molars had a close relation with the mandibular canal, while 1201 (92.7%) third molars had no direct contact. The percentage of the mandibular canal contacts with the mandibular third molar was higher when the mandibular canal was lingually positioned.

Conclusions: The anatomic structures of the mandibular third molar and the mandibular canal may be helpful to make adequate surgical planning to avoid or reduce nerve involvement.

Keywords: Anatomic three-dimensional relationship; Cone-beam computed tomography; Inferior alveolar nerve; Mandibular third molar.

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Conflict of interest statement

The authors declare that they have no conflict of interest.

Figures

Fig. 1
Fig. 1
Classification of position and contact relation of the mandibular canal in relation to the mandibular third molar. Position of the mandibular canal in relation to the roots of the mandibular third molar was classified into four classes. Class I: apical position a no contact; b contact with a complete white line; c contact with a defective white line; d penetration of the mandibular canal. Class II: buccal position e no contact; f contact with a complete white line; g contact with a defective white line; h penetration of the mandibular canal. Class III: lingual position (i) no contact; (j) contact with a complete white line; k contact with a defective white line; l penetration of the mandibular canal. Class IV: interradicular position m contact with a defective white line; n penetration of the mandibular canal. No contact and contact with a complete white line of interradicular position were not found in this study (arrow indicates the mandibular canal)
Fig. 2
Fig. 2
Vertical position of the mandibular third molar and the mandibular canal according to the penetration depth. Vertical status of the mandibular third molar and the mandibular canal was categorized in two conditions: a the root at the upper half of the mandibular canal; b the root at the lower half of the mandibular canal (arrow indicates the mandibular canal)
See this image and copyright information in PMC

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