Analysis of anatomic relationship between mandibular canal and the roots of impacted mandibular third molar by cone beam computed tomography

AIM: To analyze the anatomic relationship between mandibular canal and the roots of impacted mandibular third molar by cone beam computed tomography(CBCT).METHODS:15174 teeth in 7751 patients were diagnosed as the impaction of mandibular third molar in the author's hospital from April 2010 to April 2012.518 teeth in 401 patients showed roots overlapping with mandibular canal on panoramic radiography were examined by CBCT.During tooth extraction the relationship between mandibular canal and the roots of the impacted teeth was observed.Statistics analysis was performed by χ2 test.RESULTS:On CBCT 343 of the 518 teeth(66.22%)showed root in touch with mandibular canal,mostly the canal was between 2 roots of the molars followed by on the lingual side,below the root tip and on the buccal side(P﹤0.05).During tooth extraction exposure of the inferior nerve was found in 87 teeth(16.80%) which were shown roots overlapping with mandibular canal on panoramic radiography,while in 25.36%(87/343) on CBCT(P﹤0.05).CONCLUSION: CBCT can provide more precise information than panoramic radiography for the analysis of anatomic relationship between mandibular canal and the roots of impacted mandibular third molar.