Evaluation of the mental foramen and the mandibular canal course in emirati population: a cone-beam computed tomography study

Abstract

Background: The mandibular canal (MC) is an important bony structure presents in the mandible that contains a bundle of nerves and vessels including the inferior alveolar nerve (IAN) and the mandibular division of the trigeminal nerve (V3). During surgical or non-surgical dental treatment physical damage can occur to the contents of the inferior alveolar canal. Therefore, a comprehensive knowledge of the anatomy of the MC, its variants and relation to other anatomical structures is essential in the prevention and management of any damages to the IAN during surgical and non-surgical endodontic therapies involving mandibular teeth. It has been recommended to use CBCT to locate the MC course and relation to mandibular teeth prior to endodontic surgical procedures. Furthermore, due to its availability and its conservative nature, CBCT have been used as a tool to study the morphological characteristics of the MC, its course and its intra-bony location of different ethnic groups.

Aim: The aim of this study was to Describe the morphological characteristics of the MC, its intra-bony location, and relation to the apices of mandibular posterior teeth in an Emirati subpopulation, using CBCT.

Material and methods: This was a retrospective study designed to analyze the cone-beam computed tomography scans of Emirati patients who were treated at Healthpoint Dental Center (Mubadala, Abu Dhabi), United Arab Emirates, between 2017- 2018. 3700 CBCT scans were taken during that period as part of a treatment plan and 154 scans were selected for this study according to inclusion/exclusion criteria. Every patient treated at HDC signs a consent form which allows for research use of available patient data. All CBCT scans were acquired using Orthophos SL (Dentsply Sirona, USA) using a standard imaging protocol (CBCT at HDC are taken by same technician, using same CBCT machine with same parameters; 85 Kv, 7 mAs, with exposure time of 5 seconds and voxel size of 0.15 mm). The data were extracted and anonymized to remove all patient identifiers. The principal investigator (author) evaluated all scans on diagnostic quality monitors.

Results: 154 CBCT scans were examined. Examining the selected patients’ scans details showed that 72 patients (46.8%) were female, while 82 patients (53.2%) were male. Selected patients’ age ranged from 16 to 71 years; more specifically, 26% were younger than or aged 30, 28.5% were between 31 and 40 years and 45.5% were older than 40 years. Overall, the mean distance of the mental foramen (MF) in relation to the line between the mandibular premolars was distal by 0.83mm ± 1.84. The mean distances of the root apices with the superior border of the MC in relation to the second premolar, mesial and distal roots of the first molar and mesial and distal roots of the second molar were 4.02mm ± 2.02, 4.54mm ± 1.96, 4.07mm ± 2.08, 2.58mm ± 1.79 and 2.06mm ± 1.83 respectively. The mean distances between the buccal aspect of the mandible with the MC in relation to the second premolar, mesial and distal roots of the first molar and mesial and distal iii roots of the second molar were 3.59mm ± 1.03, 4.52mm ± 1.13, 5.05mm ± 1.21, 5.11mm ± 1.27 and 4.83mm ± 1.36 respectively. The mean distances between the lingual aspect of the mandible with the MC in relation to the second premolar, mesial and distal roots of the first molar and mesial and distal roots of the second molar were 2.79mm ± 1.03, 1.92mm ± 0.8, 1.68mm ± 0.68, 1.77mm ± 0.69 and 1.73mm ± 0.74 respectively. The mean distances between the inferior border of the mandible with the MC in relation to the second premolar, mesial and distal roots of the first molar and mesial and distal roots of the second molar were 6.6mm ± 1.61, 5.52mm ± 1.41, 5.16mm ± 1.24, 5.11mm ± 1.36 and 5.46mm ± 1.51 respectively. Statistical analysis showed that for the MF location there is no significant deference found between males and females (males -0.3mm ± 2.2 and females -0.5mm ± 2.4) (P=0.635). however, the distances between root apices of mandibular teeth to the MC was significantly higher in males compared to females. Interestingly, all mean distances were higher in males compared to females except for the distance between the lingual aspect of the mandible and the IAC in relation to the mesial root of the second molar where females had greater distance compared to males (males 1.4mm ± 0.7 females 1.9mm ± 0.7) (P < 0.001). The statistical analysis showed that there is a negative relationship between age and the location of the MF in relation with the premolars (P<0.001). On the other hand, distances between the root apices and the IAC have a significant positive relationship with age.

Conclusion: The most common location of the mental foramen is distal to the contact area between the mandibular first and second premolars (0.83mm ± 1.84), and this distance have a negative relationship with age. The distal root of the mandibular second molar is the closest root to the mandibular canal (2.06mm ± iv 1.83). The distance between the root apices of the mandibular teeth and the mandibular canal has a positive relationship with age and gender, as young female patients have smaller distance than older male patients. The common course of the canal being more lingual and inferior posteriorly and becoming more buccal and superior towards the mental foramen.