Assessment of the Retromolar Canal in Taiwan Subpopulation: A Cross-Sectional Cone-Beam Computed Tomography Study in a Medical Center.

Yen-Wen Shen,Jui-Ting Hsu,Ming-Tzu Tsai,Lih-Jyh Fuh,Wan-Chun Chang,Heng-Li Huang

doi:10.3390/tomography7020020

Abstract

The retromolar canal is an anatomical variation that occurs in the mandibular bone. The retromolar canal typically originates in the mandibular canal on the distal side of the third molar and extends forward and upward to the retromolar foramen (RMF), which contains the neurovascular bundle. Accidentally damaging the neurovascular bundle in the retromolar canal during the extraction of the third molar, dental implant surgery, or maxillofacial orthognathic surgery may lead to subsequent complications such as incomplete local anesthesia, paresthesia, and bleeding during operation. The objective of this study was to investigate the prevalence of the RMF in the Taiwanese population in a medical center by using dental cone-beam computed tomography (CBCT) and to identify the position of the RMF in the mandibular bone. The dental CBCT images for the mandibular bone of 68 hemi-mandible were uploaded to the medical imaging software Mimics 15.1 to determine the prevalence of the RMF in the Taiwanese population and the three positional parameters of the RMF in the mandibular bone: (1) The diameter of the RMF, (2) the horizontal distance from the midpoint of the RMF to the distal cementoenamel junction of the second molar, and (3) the vertical distance from the midpoint of the RMF to the upper border of the mandibular canal. Seven RMFs were observed in the 68 hemi-mandibles. Thus, the RMF prevalence was 10.3%. In addition, the diameter of the RMF was 1.41 ± 0.30 mm (mean ± standard deviation), the horizontal distance from the midpoint of the RMF to the distal cementoenamel junction of the the second molar was 12.93 ± 2.87 mm, and the vertical distance from the midpoint of the RMF to the upper border of the mandibular canal below second molar was 13.62 ± 1.3487 mm. This study determined the prevalence of the RMF in the Taiwanese population in a medical center and its relative position in the mandibular bone. This information can provide clinicians with a reference for posterior mandible anesthesia and surgery to ensure medical safety.

Highlights

Ossenberg et al [3] discovered a high proportion of retromolar foramen (RMF) in adolescents’ mandible, and speculated that its appearance may be related to the sudden acceleration in physical development during adolescence and the adolescent growth spurt and eruption of the wisdom teeth that require more nerves and blood vessels
In terms of the prevalence of RMFs in different sexes, three and four RMFs were observed in the hemi-mandibles of 30 men and 38 women, respectively, indicating a respective RMF prevalence of 10% and 10.5%
In terms of RMF prevalence in the left and right mandibles, three RMFs were observed in 33 left mandibles (9.1%), and four RMS were recorded in 35 right mandibles (11.4%)

Summary

Introduction

The retromolar fossa, in the form of a triangular depression, can be observed between the temporal crest medially and the anterior border of the ramus of the mandible laterally [1]. This region is covered by elevated mucosa of variable size [2]. The retromolar canal, an anatomical variation that occurs in the posterior mandible, is rarely mentioned in dentistry textbooks, and relevant studies have highlighted numerous differences and uncertainties. Ossenberg et al [3] discovered a high proportion of retromolar foramen (RMF) in adolescents’ mandible, and speculated that its appearance may be related to the sudden acceleration in physical development during adolescence and the adolescent growth spurt and eruption of the wisdom teeth that require more nerves and blood vessels

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