Purpose: The extraction of impacted mandibular third molar is associated with various types of intraoperative and postoperative complications, one of them is injury to lingual nerve. The present study aims to assess and correlate the variation in lingual cortical plate thickness with different angulations and determine the topographic relationship between the root apex of impacted mandibular third molar and lingual cortical plate using Cone Beam Computed Tomography (CBCT).
Methods: This prospective cohort study enrolled 140 patients with impacted mandibular third molars who underwent preoperative CBCT imaging. The CBCT images were used to evaluate the outcome variables such as lingual cortical plate thickness and topographical relationship between root apex of impacted mandibular third molar and lingual cortical plate. The predictor variables included age, gender, inclination of third molar, mesiodistal angle, buccolingual angle and lingual plate morphology.
Results: The temporary lingual nerve paresthesia was reported by 1 patient (0.71%) out of 140 patients. The lingual bone in distoangular and vertical impacted third molar was found to be 1.20 times thicker than mesioangular and horizontal teeth. Lingual bone thinning at mid-root level was observed in maximum number of cases with mesioangular teeth (68.5%), whereas horizontal impacted teeth showed lingual bone thinning (90.9%) at root apex level. The mean buccolingual angle of impacted mandibular third molar was found to be significantly associated with lingual bone perforation (p value = 0.0258). The morphology of lingual plate was observed as undercut type (37.14%) followed by slanted (36.43%), parallel (19.29%) and round type (7.14%).
Conclusion: Increase in buccolingual angle of impacted mandibular third molar decreases lingual bone thickness which is the natural barrier for protecting injury to lingual nerve. Also undercut and slanted lingual plate shapes were recognised as risk factors for contact/perforation between root apex and lingual plate. Therefore, proper screening and planning of high risk patients before third molar extraction is crucial.
Keywords: Cone-beam CT; Impacted mandibular third molar; Lingual bone perforation; Lingual nerve injury; Lingual plate morphology; Lingual plate thickness.
© The Association of Oral and Maxillofacial Surgeons of India 2022. Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.