When extracting a mandibular impacted third molar, understanding the positional relationship between the third molar and mandibular canal is important for assessing the risk of paresthesia of the inferior alveolar nerve. In particular, dental cone-beam CT (CBCT) is useful for preoperative evaluation.
This study included 637 teeth in 543 cases with a mandibular impacted third molar extracted by both panoramic radiography and CBCT. The relationship of these cases to paresthesia of the inferior alveolar nerve was retrospectively investigated based on the medical records and imaging findings. The study included age, gender, site, years of surgeons’ experience, panoramic radiography findings, and CBCT findings.
The rate of paresthesia of the inferior alveolar nerve associated with tooth extraction was 5.5%. In univariate analysis, there were significant differences in panoramic radiography findings between the class and position of the Pell-Gregory classification, clarity of the upper wall white line of the mandibular canal, the positional relationship between the mandibular canal and root; in CBCT findings of the bucco-lingual position of the root and mandibular canal, the cross-sectional morphology of the mandibular canal, and presence or absence of bone. In multivariate analysis, there were significant differences in the class of the Pell-Gregory classification and the cross-sectional morphology of the mandibular canal.
The present study suggests that CBCT imaging should be considered in cases with Pell-Gregory classification Class Ⅲ on panoramic radiographs and the position of the mandibular impacted third molar and the mandibular canal crossing at the inferior wall of the mandibular canal.
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