Classification of the impacted mandibular third molar using the mandibular canal as a reference and its clinical significance

Abstract

Abstract: PURPOSE: The purpose of this study was to access the position of third mandibular molar in relationship to the inferior alveolar nerve(IAN) injury during surgical extraction. METHODS: Six hundred and fifty-eight cases were diagnosed with impacted mandibular third molars(ITIMs) which were intersected with the inferior alveolar canal(IAC) by cone beam computed tomography(CBCT), they were classified using the IAC as a reference, the relationship of tooth root and IAC was divided into four types: ① The root was located above the IAC (type 1); ②The root was located on the buccal side (type 2); ③The root was located on the lingual side (type 3); ④ IAC was located between the roots (type 4). In all cases, the teeth were surgically extracted, and postoperative observations were performed to determine the category which was more likely to cause IAN damage. The data was analyzed with SPSS13.0 sofeware package for chi-square test. RESULTS: The overall rate of neurosensory impairment following extraction was 6.8%(45/658). It occurred in 15 patients whose root was located above the IAC (15/332), in 19 patients whose root was located on the buccal side of the IAC (19/108), and in 11 patients whose root was located on the lingual side (11/210). No neurosensory impairment was found in the group where the IAC was located between the roots (0/8). Statistical analysis showed there was significant difference between type 1 and type 2, and type 2 and type 3 (χ²test, P<0.01); and there was no significant difference between the first group and the third group (χ²test, P>0.05). CONCLUSIONS: The relationship between the IMTM and the IAC was divided into four categories using the IAC as a reference. Risk of IAN damage exists for patients during surgical extractions of IMTM that are intersected with the IAC, especially for those with impacted teeth that are located on the buccal side of the IAC.

Key words: Impacted mandibular third molars, Inferior alveolar canal, CBCT

CLC Number:

R782.1

XU Guang-zhou, YANG Chi, FAN Xin-dong, YU Chuang-qi, WANG Yong, ZHANG Ying. Classification of the impacted mandibular third molar using the mandibular canal as a reference and its clinical significance[J]. China Journal of Oral and Maxillofacial Surgery, 2014, 12(2): 131-135.

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