Abstract
The present study was aimed to determine the topographic relationship between root apex of the mesially and horizontally impacted mandibular third molar and lingual plate of mandible. The original cone beam computed tomography (CBCT) data of 364 teeth from 223 patients were retrospectively collected and analyzed. The topographic relationship between root apex and lingual plate on cross-sectional CBCT images was classified as non-contact (99), contact (145) and perforation (120). The cross-sectional morphology of lingual plate at the level of root apex was defined as parallel (28), undercut (38), slanted (29) and round (4). The distribution of topographic relationship between root apex and lingual plate significantly associated with gender, impaction depth, root number and lingual plate morphology. Moreover, the average bone thickness of lingual cortex and distance between root apex and the outer surface of lingual plate were 1.02 and 1.39 mm, respectively. Furthermore, multivariate regression analyses identified impaction depth and lingual plate morphology as the risk factors for the contact and perforation subtypes between root apex and lingual plate. Collectively, our findings reveal the topographic proximity of root apex of impacted mandibular third molar to the lingual plate, which might be associated with intraoperative and postoperative complications during tooth extraction.
Highlights
Depth and angulation of impaction, et al.[6,9,13]
Tolstunov and his colleagues reported that fenestration in the lingual plate identified by cone beam computed tomography (CBCT) scan was more commonly observed than originally expected at the third molar apex region and such fenestration of lingual bone was significantly associated with the angulation of the impacted third molar[29]
A line of evidence has suggested that the thin and shape of lingual cortical plate as well as perforation or fenestration in lingual plate are associated with accidental displacement of third molars or root fragments, secondary infection of submandibular space and lingual nerve injury following surgical extraction of impacted third molars[8,10,26,31]
Summary
Depth and angulation of impaction, et al.[6,9,13]. Currently, identifying the relevant risk factors associated with complications during and after the impacted third molar surgery primarily depends on presurgical radiographic examinations. From CBCT data of 110 deeply impacted mandibular third molars, the authors reported that 87.3% teeth were classified as lingual position according to their classification based on the deduction values of buccal-lingual alveolar bone thickness[13]. These abovementioned findings support the notion that these anatomic factors might contribute to fracture of lingual plate, root displacement as well as lingual nerve injury after extraction of impacted mandibular third molars. The aim of this study was to measure the thickness of the lingual plate at the level of root apex of impacted mandibular third molar and determine the topographic relationship between the root apex and lingual plate using CBCT images. We sought to identify the potential associated factors with the perforation of lingual plate at this region
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