Morphology and Variant Anatomy of the Mandibular Canal in a Kenyan Population: a Cone-beam Computed Tomography Study

Abstract

BACKGROUND: The mandibular canal (MC) is a bony conduit within the mandible originating from the mandibular foramen and terminating at the ipsilateral mental foramen (MF). It transmits the inferior alveolar neurovascular bundle. It exhibits surgically significant anatomical variations in its course and terminal segment among different ethnic groups. Detailed knowledge of the anatomy of this canal in the local population is important in guiding surgeons to avoid inadvertent injury to the neurovascular bundle during surgical procedures. STUDY OBJECTIVE: To investigate and document the normal morphology and variant anatomy of the MC in a select Kenyan population using cone-beam computed tomography (CBCT) scans. METHODOLOGY: This was a retrospective descriptive cross-sectional CBCT study. Quantitative techniques were used to collect morphometric data on the MC and its variants. The study was conducted at a private imaging facility called Dental and Maxillofacial Imaging Centre (DAMIC) in Nairobi, Kenya. The study sample was selected from DAMIC’s electronic CBCT database using a non-probability sampling method. Data was collected using a data extraction form in a Microsoft Excel database. It was then exported to Statistical Product and Service Solutions (SPSS) version 24 software for statistical analysis. A p-value <0.05 was considered statistically significant. RESULTS: 351 hemi mandibular CBCT scans from 202 patients were included in this study. 142 scans were from 81 (40.1%) male and 209 scans were from 121 (59.9%) female patients. The mean age was 40.4±14.2 years. The most frequently encountered course of the MC was the progressive descent type seen in 241 (68.7%) scans. Accessory MC were observed in 15 (4.3%)

scans. Accessory MF were observed in 29 (8.3%) scans. Only one CBCT scan showed both accessory MC and accessory MF in the same patient. The mean diameter of the MC was 3.36±0.39mm. The most frequent position of the main MF in relation to the second premolar was anterior (53.3%). The average distance from the MF to the IBM was 12.17±1.91mm. The anterior loop of mental nerve (ALMN) was observed in 18 (5.1%) scans. The mean length of the ALMN was 4.83±0.89mm. CONCLUSIONS: The progressive descent and straight projection types were the most and least predominant courses of the MC encountered respectively. The prevalence of accessory MC and accessory MF in this study was relatively low. The presence of accessory MF was not invariably associated with the presence of accessory MC. The orientation of the MC was more lingual towards the angle of the mandible and more buccal towards the MF. The predominant position of the MF was anterior to the second premolar. The prevalence of the ALMN in this study was low but its average length was clinically significant. RECOMMENDATIONS: To fully understand the anatomic variations of the MC, there is a need for multicentric studies with properly defined anatomical landmarks to quantify and precisely predict these variations. scans. Accessory MF were observed in 29 (8.3%) scans. Only one CBCT scan showed both accessory MC and accessory MF in the same patient. The mean diameter of the MC was 3.36±0.39mm. The most frequent position of the main MF in relation to the second premolar was anterior (53.3%). The average distance from the MF to the IBM was 12.17±1.91mm. The anterior loop of mental nerve (ALMN) was observed in 18 (5.1%) scans. The mean length of the ALMN was 4.83±0.89mm. CONCLUSIONS: The progressive descent and straight projection types were the most and least predominant courses of the MC encountered respectively. The prevalence of accessory MC and accessory MF in this study was relatively low. The presence of accessory MF was not invariably associated with the presence of accessory MC. The orientation of the MC was more lingual towards the angle of the mandible and more buccal towards the MF. The predominant position of the MF was anterior to the second premolar. The prevalence of the ALMN in this study was low but its average length was clinically significant. RECOMMENDATIONS: To fully understand the anatomic variations of the MC, there is a need for multicentric studies with properly defined anatomical landmarks to quantify and precisely predict these variations.