Incidence and Anatomical Properties of Retromolar Canal in an Iranian Population: A Cone-Beam Computed Tomography Study

Abstract

Objectives. Retromolar canal (RC) is an anatomic structure, and due to increasing demand for surgical procedure in the retromolar area of the mandible, the identification of the retromolar canal has become an issue of clinical concern. It can innervate the third molar and some of the muscles around the posterior segment of the mandible, complicating surgical procedures in the retromolar area and root canal treatment of third molars. The aim of this study was to evaluate the incidence and anatomical properties of RC in a western Iranian population using cone-beam computed tomography (CBCT) images. Materials and Methods. Two hundred bilateral CBCT images were collected and screened in the three spatial planes for the presence of an RC. Anatomical properties and location of the RCs were assessed according to their course and distance from the surrounding structures. The relationship between the presence of RC and age, sex, side, and presence of second and third molars was also evaluated. Independent samples t-test, ANOVA, Tukey’s post hoc test, paired t-test, and chi-square were used to compare groups. Results. At least one RC was observed in 22% of the mandibles. Its bilateral incidence was 5.5%. Two major types of canals were detected, namely, type I, following a straight or curved course from the mandibular canal (MC) to the retromolar area (47.3%), and type II, coursing from the retromolar area to the radicular part of the third molar (52.7%). Regarding linear measurements, the mean RC diameter and the mean distance to the MC, second, and third molars were 0.68 ± 0.31, 13.7 ± 2.8, 15.3 ± 3.0, and 7.3 ± 2.3 mm, respectively. Conclusion. Based on the results of this study, RC was found in 22% of the cases; thus, it should be considered as a normal anatomical variation in the Iranian population rather than a rare finding.

Prevalence and morphometric analysis of the retromolar canal in a Spanish population sample: a helical CT scan study

“…(2013) ( 5 ). In our study, the observed prevalence was 23.1%, which coincides with other studies based on CBCT with similar sample sizes ( 8 , 19 ). There may be several causes for the different prevalence indicated by several studies, such as the applied anatomical definition of the RMC, different sample sizes in studies, samples’ distinct population origins, study designs, e.g.…”

“…According to the unilateral canals, we found that right canals were more frequent than left canals, just as Nikkerdar et al . reported, but with no significant differences ( 8 ). Nevertheless, higher prevalences have been described for left canals ( 5 , 21 ).…”

“…Some classifications do not include types II and IV because they do not communicate with the MC. This fact also comes over in those works that consider the RMC to be a BMC type, which could imply underestimating the real RMC prevalence, and it could be worse if we bear in mind that some studies have described type II as the most prevalent RMC type ( 5 , 6 , 8 ).…”

“…As soon as the presence of the RMC was confirmed, it was classified according to the typology described by N. Nikkerdar (2020) ( 8 ) (Fig. 1 ).…”

Retromolar canal – an essential structure that is often forgotten

“…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.…”