2021, Number 4
Anatomical relationship of the mandibular canal and root apices: CBCT analysis in a Guatemalan population
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ABSTRACT
Introduction: the anatomical proximity of the mandibular canal and the roots of mandibular posterior teeth poses a risk of injury during various dental procedures in that region. Objective: the aim of the study was to evaluate the anatomic relationship between the mandibular canal and the root apices of mandibular premolars and molars in a Guatemalan population. Material and methods: the distances from the mandibular canal to the root apices and their buccolingual relationship were evaluated. 172 cone-beam computed tomographies (CBCT) were studied. The distances were measured in millimeters from the mandibular canal to the apices of second premolars, the mesial and distal root of first molars, and the mesial and distal root of second molars. The buccolingual position of the mandibular canal in relation to the apices was classified as 1 = buccal; 2 = central; 3 = lingual. Results: it was determined that the mandibular canal is closer to the apices of distal roots of second molars, with a mean distance of 2.82 mm. Besides, it was observed that the mandibular canal is found, in greater proportion, in a lingual position at the level of the first and second mandibular molar and adopts a buccal position at the level of the second mandibular premolar. Conclusions: this study shows that the closest distances to the mandibular canal are at the level of the second molars and that the mandibular canal changes position from lingual to buccal in its posterior-anterior path.INTRODUCTION
The anatomical relationship between the mandibular canal and the root apices of mandibular posterior teeth is of academic and practical importance to the dental professional. The inferior alveolar nerve is a branch of the mandibular nerve, a branch of the trigeminal nerve, and is located within the mandibular canal, spanning from the mandibular foramen to the mentonian foramen.1
Knowledge of the location and configuration of the mandibular canal is important prior to perform surgical and dental procedures involving the mandible. Because of its anatomical relationship with the apices of lower molars and premolars, the inferior alveolar nerve is at risk of trauma during procedures such as implant placement, endodontic treatment, or exodontia.2 Damage to the inferior alveolar nerve can cause neuropathies such as pain, paresthesia, or anesthesia in the mandibular region, which result in an unpleasant sensation for the patient and can alter basic functions such as speech or mastication.3,4
The present study aims to investigate and report the distances from the mandibular canal to the root apices of the mandibular posterior teeth in Guatemalan patients. In addition, it seeks to evaluate the buccolingual relationship of the mandibular canal within the mandibular bone in relation to the apices. A specific measuring instrument will be used to carry out the study: cone-beam computed tomography, which provides an adequate image and accurate measurements for the evaluation of anatomical structures.
MATERIAL AND METHODS
The present is a descriptive, non-experimental, cross-sectional study, which evaluated the distance from the mandibular canal to the root apices and their relationship in the buccolingual direction.
The study was carried out in the Radiology clinic of the Faculty of Dentistry of the University of San Carlos of Guatemala, in the period from January to November 2018. We proceeded to request administrative permissions from the corresponding authorities to perform the analysis of CBCT cone-beam computed tomography scans found in the database of the said clinic, of Guatemalan patients who attended the Faculty of Dentistry of the University of San Carlos of Guatemala in 2017. The aspect of patient confidentiality will be observed. The sample was selected based on the criteria in Table 1.
Procedure: images were obtained in a coronal slice of the most apical portion of the roots of each tooth to be evaluated in the study.
- 1. In order to evaluate the distance from the mandibular canal to the root apices:
- a. The OnDemand 3D Dental™ software measurement tool was used to draw a line from the most apical point of each root to the nearest cortical part of the mandibular canal (Figure 1).
- b. Measurements were obtained in millimeters, one for each root.
- 2. To assess the position of the mandibular canal in relation to the root apices:
- a. The tracing tool of the OnDemand 3D Dental™ software was used to draw a line from the most apical point of each root toward the most inferior part of the mandibular bone.
- b. They were classified into groups according to the position of the canal in relation to the previously drawn line. Group 1 = buccal: the mandibular canal was buccal to the drawn line; group 2 = central: the mandibular canal was central to the drawn line; group 3 = lingual: the mandibular canal was lingual to the drawn line (Figure 2).
- 3. The measurement and the buccolingual relationship were collected in the data collection and processing instrument and the results were obtained.
The analysis of the collected data was performed with the IBM SPSS® statistical program. Mean and standard variation values will be used to determine the average distances from the mandibular canal to the root apices.
RESULTS
A total of 172 tomographies were analyzed (females = 58.7%, males = 41.3%), with a mean age of 39 years. For each tomography, five measurements were performed at different levels: second premolar, the mesial root of the first molar, the distal root of the first molar, the mesial root of the second molar, the distal root of the second molar. A total of 516 teeth were evaluated, taking 860 measurements from the mandibular canal to a root apex.
Mean distances of 3.54, 4.35, 4.31, 3.19, 2.82 mm were obtained, respectively, for the second premolar, the mesial root of the first molar, the distal root of the first molar, the mesial root of the second molar, the distal root of the second molar (Table 2).
For the mean distances obtained from the CT scans evaluated, it was determined that the root apices with the closest proximity to the mandibular canal were the apices of the distal roots of the second molars, with an average distance of 2.82 mm. In addition, it was determined that the root apices with the greatest distance to the mandibular canal were the apices of the mesial roots of the first molars, with a distance of 4.35 mm.
To evaluate the position of the mandibular canal with respect to the root apices, five evaluations were made at different levels: second premolar, the mesial root of the first molar, the distal root of the first molar, the mesial root of the second molar, the distal root of the second molar.
Regarding the buccolingual position, it was determined that at the level of the second premolar, in the majority (78%) the canal is in a buccal position; at the level of the first molar in its mesial root, in the majority (68.6%) the canal is in a lingual position; at the level of the first molar in its distal root, in the majority (88.9%) the canal is in a lingual position; at the level of the second molar at its mesial root, in the majority (73.1.%) the canal is in a lingual position; at the level of the second molar at its distal root, in the majority (71.9%) the canal is in a lingual position (Figure 3).
DISCUSSION
Several studies have reported the complications that can arise from damage to the mandibular canal during endodontic or implantological procedures. This damage is often due to a lack of knowledge regarding the proximity of the root apexes of the mandibular posterior teeth to surrounding structures such as the mandibular canal.5,6
The use of cone-beam computed tomography measurements has been proven as a valid and accurate method for the measurement of anatomical structures.7,8
In the study performed, it was observed that the root apices closest to the mandibular canal are the distal and mesial apices of the second molar, with average distances of 2.82 and 3.19 mm respectively. Closeness to the mandibular canal was also observed for the second premolar with a distance of 3.54 mm. On the other hand, it was determined with the data obtained that the greatest distances are the apices of the first molar, both mesial and distal, with a value of 4.3 mm.
Similar results to ours were reported by Dale Denio in 1992, after evaluating dissected mandibles measuring the distance from the mandibular canal to the apices of the mandibular premolars and molars, in which he reported greater proximity of the apices of the second molar and second premolar to the mandibular canal.9 Littner also found in his study the greatest approximation with the distal root of the second molar and the most distant with the mesial root of the first molar.10
The results observed in our study are also related to and support the data published by Orstavik, who concluded that the second molars and second premolars were the teeth with the greatest association with lip paresthesia after endodontic procedures, due to their proximity to the mandibular canal and, therefore, to the inferior alveolar nerve.11
Regarding the buccolingual position, the results obtained show that the canal in the population evaluated runs mostly in a lingual position to the root apices and at the level of the second premolar it is located in a buccal or vestibular position. This was reported by the study of Olivier, who also reported the relationship of the premolar and molar apices to the mandibular canal. He found that the mandibular canal is in a lingual position at the molar roots and in a buccal position at the level of the premolar apices. Olivier describes this pattern of mandibular canal position as an "S-shape".2
Dental professionals should be aware of the location of the mandibular canal before performing invasive procedures on the mandible such as implant placement, endodontic treatment, or extractions to avoid damage to the inferior alveolar vasculonervous bundle. The differences that exist in distance and position and according to the sex and age of the patient should also be known.
CONCLUSIONS
Based on the results obtained in this study, it is concluded that:
- 1. The root apex found closest to the mandibular canal in Guatemalan patients is the distal root apex of the mandibular second molar.
- 2. In a higher percentage, the mandibular canal in Guatemalan patients evaluated is in a lingual position with respect to the distal and mesial roots of the first and second mandibular molar, and it changes its position at the level of the second mandibular premolar and is located in a buccal position itself.
REFERENCES
AFFILIATIONS
1 Facultad de Odontología, Universidad de San Carlos de Guatemala.
CORRESPONDENCE
Daniel Francisco Díaz Samayoa. E-mail: danydiazs@hotmail.comReceived: Abril 2020. Accepted: Junio 2020.