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

Liqun Gu,Zhangui Tang,Xianchu Liu,Chao Zhu,Kejia Chen

doi:10.1007/s00276-017-1928-6

Liqun Gu, Zhangui Tang + Show 3 more

Open Access

https://doi.org/10.1007/s00276-017-1928-6

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Abstract

PurposeThe 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.MethodsThis 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.ResultsOn 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.ConclusionsThe 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.

Highlights

Extraction of mandibular third molars is the most widely performed oral and maxillofacial surgery
On a total of 1296 third molars, the mandibular canal in relation 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 between the roots (0.5%)
inferior alveolar nerve (IAN) injury is a serious complication after extraction of the mandibular third molar, affecting the function of the stomatognathic system and the quality of life of patients

Summary

Introduction

Extraction of mandibular third molars is the most widely performed oral and maxillofacial surgery. Neurological injury is a rare but serious complication undergoing the operation. The incidence of inferior alveolar nerve (IAN) injury ranges from 0.4 to 6% [3, 4, 30]. Damage to IAN occurs most frequently when the mandibular third molar has a close relationship with the mandibular canal [29]. Imaging examination is the first step to assess the risk of IAN injury before operation. The presence of certain radiographic signs on panoramic radiograph indicates a raised risk of IAN involvement. There are some overlapping images which make it hard to precisely judge the positional relationship, especially in the buccolingual direction [19, 21, 27]

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