Prevalence and Characteristics of Accessory Mandibular Canals: A Cone-Beam Computed Tomography Study in a European Adult Population

Abstract

The purpose of this observational study is to evaluate the prevalence and main characteristics of bifid canals within a European adult population, analyzing cone-beam-computed tomography (CBCT). The population study examined 300 subjects. The CBCTs were performed between 2012 and 2019, using PaX-Zenith3D with a standard protocol of acquisition. The parameters analyzed were the presence and lengths of the bifid mandibular canals. The sample included 49% male and 51% female participants. The mean age of the patients was 47.07 ± 17.7 years. Anatomical variants of the mandibular canal were identified in 28.8% of the sides and 50.3% of the patients. In 7.3% of the subjects, the anatomical variants were present bilaterally. The most frequently encountered bifid canal was Type 3 (40.5%), followed by the Type 1 canal (39.3%), the Type 2 canal (14.5%), and the Type 4 canal (5.9%), 40% on the right side and 60% on the left side. The average length of the bifid canals located on the right side of the mandible was 11.96 ± 5.57 mm, compared to 11.38 ± 4.89 mm for those measured on the left side. The bifid mandibular canal is a common anatomical variation of the mandibular canal. It is fundamental to performing an accurate preoperative evaluation using CBCT analysis to avoid and/or reduce intraoperative and postoperative complications.

Keywords: accessory mandibular foramina; bifid canals; inferior alveolar nerve; mandibular canal variant.

Figure 1

Diagram of the different classifications [12,13,15,16,17].

Figure 2

Naitoh classification. The forward canal divided into one with confluence (A) or one without confluence (B). The bucco-lingual canal from the buccal or lingual wall (C,D). The dental canal reaches the root apex (E). The retromolar canal opens into the retromolar region (F). Reprinted with permission from [18] Copyright (2019).

Figure 3

Measuring the length of a Type 1 canal.

Figure 4

Angle measurement of a Type 1 canal.

Figure 5

Type 1, retromolar canal: (A) sagittal view; (B) intraoperative view; (C) Panorex reconstruction; and (D) cross-section reconstruction. Arrow indicated the presence of the canal.

Figure 6

Type 2, dental canal: cross and Panorex reconstructions. Reconstruction shows arrival at the apex of the 4.7 tooth element.

Figure 7

Type 3, confluent anterior canal: (A) Panorex and (B) cross-section reconstructions. Arrows indicate the presence of the canal.

Figure 8

Type 3, not confluent canal: (A–D) cross-section reconstructions and (E) Panorex reconstructions. Arrows indicate the presence of the canal.

Figure 9

Type 4: (A) buccal canal cross-section reconstructions and (B) lingual cross-section reconstructions. Arrows indicate the presence of the canal.