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What are the retromolar and bifid/trifid mandibular canals as seen on cone-beam computed tomography? Revisiting classic gross anatomy of the inferior alveolar nerve and correcting terminology

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Abstract

Purpose

Since cone-beam computed tomography was developed, a number of radiological studies on the bifid mandibular canals (BMCs) and trifid mandibular canals (TMCs) have been reported. However, many of the suggested subtypes of the BMC described in the literature seem to be normal branches of the inferior alveolar nerve. This might be due to a lack of revisiting classic anatomical studies in the field of radiology. Therefore, such studies are revisited here.

Methods

A database search using PubMed and Google Scholar was conducted on BMC and TMC. Eighty-nine articles underwent full-text assessment. The reported three classifications of BMC and the six modified classifications were reviewed and compared to the intramandibular inferior alveolar nerve branches.

Results

Some subtypes of BMC and TMC simply represent normal inferior alveolar nerve branches, i.e., retromolar branch, molar branch (alveolar branch/dental branch), large mental branch, or communicating branch. Others such as Naitoh’s type III BMC and forward canal might be a true BMC.

Conclusion

We found that the bifid mandibular canal is an additional intramandibular canal running parallel to the mandibular canal with/without confluence with the main canal through comparison of classifications of BMC/TMC between the radiology and anatomy fields.

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Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

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Authors and Affiliations

  1. Department of Neurosurgery, Tulane Center for Clinical Neurosciences, Tulane University School of Medicine, 131 S. Robertson St. Suite 1300, New Orleans, LA, 70112, USA

    Joe Iwanaga & R. Shane Tubbs

  2. Department of Neurology, Tulane Center for Clinical Neurosciences, Tulane University School of Medicine, New Orleans, LA, USA

    Joe Iwanaga & R. Shane Tubbs

  3. Dental and Oral Medical Center, Kurume University School of Medicine, Kurume, Fukuoka, Japan

    Joe Iwanaga

  4. Division of Gross and Clinical Anatomy, Department of Anatomy, Kurume University School of Medicine, Kurume, Fukuoka, Japan

    Joe Iwanaga

  5. Department of Oral and Maxillofacial Radiology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan

    Yohei Takeshita

  6. University of Texas Health Science Center at Houston School of Dentistry, Houston, USA

    Yuki Matsushita

  7. Department of Anatomy, Catholic Kwandong University College of Medicine, Gangneung, Korea

    Mi-Sun Hur

  8. Department of Oral and Maxillofacial Surgery, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan

    Soichiro Ibaragi

  9. Department of Anatomical Sciences, St. George’s University, St. George’s, Grenada

    R. Shane Tubbs

  10. Department of Structural and Cellular Biology, Tulane University School of Medicine, New Orleans, LA, USA

    R. Shane Tubbs

  11. Department of Surgery, Tulane University School of Medicine, New Orleans, LA, USA

    R. Shane Tubbs

  12. Department of Neurosurgery and Ochsner Neuroscience Institute, Ochsner Health System, New Orleans, LA, USA

    R. Shane Tubbs

  13. University of Queensland, Brisbane, Australia

    R. Shane Tubbs

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  1. Joe Iwanaga
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Contributions

JI: protocol/project development, data collection, data analysis, and manuscript writing. YT: protocol/project development, data collection, and manuscript writing. YM: data analysis and manuscript editing. MSH: data analysis and manuscript editing. SI: protocol/project development and manuscript editing. RST: protocol/project development, data analysis, and manuscript editing. Approval of the final version of the manuscript: all authors.

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Correspondence to Joe Iwanaga.

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Iwanaga, J., Takeshita, Y., Matsushita, Y. et al. What are the retromolar and bifid/trifid mandibular canals as seen on cone-beam computed tomography? Revisiting classic gross anatomy of the inferior alveolar nerve and correcting terminology. Surg Radiol Anat 44, 147–156 (2022). https://doi.org/10.1007/s00276-021-02862-y

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