Investigation of the Prevalence of Retromolar Canals: A Cone Beam CT Study

Abstract

SUMMARY:The retromolar canal (RMC) is a collateral branch of the mandibular canal. This branch seems to be involved in the innervation of the third molar, retromolar trigon and part of the buccal mucosa and fibres of the buccinator and temporalis muscles. The prevalence of RMC in osseous and CBCT studies was reported between 1.7 %-72 %. This study aims to investigate the prevalence of RMCs in a Turkish population using cone beam CT. 340 CBCT images of hemimandibles of 170 patients, with a mean age of 37 (range, 16-80), that clearly identified the course of the mandibular canal in the posterior mandible were selected retrospectively from the archived records of our Oral and Maxillofacial Radiology Department. The sagittal, coronal, axial and pseudopanoramic images were used for assessing the RMCs. This variant was found in 19 out of 170 patients (11 %). Of the 340 CBCT examinations in 170 patients, 20 showed the presence of a RMC (5 %). It was present unilaterally in 18 patients (95 %) and bilaterally in one patient (5 %). There was no difference in the presence of RMCs with regard to sex and sides of the mandible (p>0.05). Clinicans should be aware of RMC and this anatomical variance should be taken into consideration while planning surgery around this region. When there is any suspicion of the RMC presence CBCT is the best imaging modality to visualize the three-dimensional structure of this variant.

Retromolar canal – an essential structure that is often forgotten

“…As stated in the studies by Haas et al [6], the effectiveness of CBCT and CT in detecting the retromolar canal is almost four times higher than in the case of panoramic radiography. However, there were no significant differences in the incidence of the apical canal between females and males [5]. Some studies suggest that one side may be more often chara cterized by the presence of the retromolar canal, while other researchers have obtained results indicating that there is no such relationship and there is no significant difference in frequency between the sides of the mandible [5,13].…”

“…The tomography with a slightly higher radiation dose provides the possibility of assessing the jaw bone structures in three dimensions, which was not possible with the two-dimensional technique. On the other hand, compared to another three-dimensional technique -CT -CBCT allows for a precise examination with a lower single dose of radiation [5,11,12]. There are reports off the use of high-resolution magnetic resonance imaging to examine the mandibles of living patients and the endoscopic technique for imaging the course of the retromolar canal on "dry" cadaver mandibles [13][14][15].…”

“…They obtained different results: from the frequency of 1.7% (Ossenberg) to 75.4% (Patil et al). Such diverse results were obtained due to the use of dia gnostic techniques: CBCT, panoramic radiography and anatomical examinations on dry, macerated mandibles [5,10,[21][22][23][24][25][26][27]. As stated in the studies by Haas et al [6], the effectiveness of CBCT and CT in detecting the retromolar canal is almost four times higher than in the case of panoramic radiography.…”

“…The retromolar canal begins as a bifurcation of the bony wall of the mandibular canal and runs towards the retromolar triangle, which is limited by the temporal crest from the medial side, the anterior edge of the mandibular ramus from the lateral side and the distal surface of the mandibular third molar [3,4]. The retromolar canal contains a neurovascular bundle that is formed by thin myelin nerve fibers, veins and arterioles that are surrounded by collagen fibers along with a small amount of adipose tissue [5]. The nerve bundles running through the retromolar canal innervate the gingival mucosa of the lower premolars and molars [6].…”

“…The nerve bundles running through the retromolar canal innervate the gingival mucosa of the lower premolars and molars [6]. There are also reports on the involvement of retromolar nerve in the innervation of the area of the retromolar triangle, the pulp of third molar, a part of the cheek mucosa and the temporal muscles [5]. Haas et al [6] report that an abnormal branch for the buccal muscle…”