Observation of retromolar canals on cone beam computed tomography



To evaluate the incidence and location of retromolar canal (RMC) in an eastern Chinese population using cone beam computed tomography (CBCT) images.


Six hundred and fifty-seven patients (276 males and 381 females, 19–49 years old) from east China were enrolled. Both right and left sides of the mandible were examined (n = 1314). Two-dimensional (2D) images of various planes in the mandibular ramus region and reconstructed three-dimensional (3D) images were reviewed. The course of the RMC and the location of the retromolar foramina (RMF) were observed.


Retromolar canal (RMC) was observed in 25.9% (170/657) of patients and 15.7% of sides (206/1314). 20.4% patients had unilateral RMC (134/657) and 5.5% had bilaterally RMC (36/657). Most RMC are horizontally curved course (Type B, 45.6%), followed by vertically curved course (Type A, 44.2%). Type C RMC, which run independently from separate foramina in the mandibular ramus, were relatively rare (10.2%). The distance from the middle of the RMF to the distal end of the second molar ranged from 4.56 to 24.01 mm and the mean distance was 11.97 mm.


RMC is not a rare anatomical structure in the eastern Chinese population. CBCT should be applied as a diagnostic tool to provide detailed information involving the retromolar area.

This is a preview of subscription content, access via your institution.

Fig. 1
Fig. 2
Fig. 3


  1. 1.

    Alves N, Deana NF. Anatomical and radiographical study of the retromolar canal and retromolar foramen in macerated mandibles. Int J Clin Exp Med. 2015;8(3):4292–6.

    PubMed  PubMed Central  Google Scholar 

  2. 2.

    Naitoh M, Hiraiwa Y, Aimiya H, Ariji E. Observation of bifid mandibular canal using cone-beam computerized tomography. Int J Oral Max Implant. 2009;24(1):155–9.

    Google Scholar 

  3. 3.

    Chavez-Lomeli M, Mansilla Lory J, Pompa J, Kjaer I. The human mandibular canal arises from three separate canals innervating different tooth groups. J Dent Res. 1996;75(8):1540–4.

    PubMed  Article  Google Scholar 

  4. 4.

    Kuribayashi A, Watanabe H, Imaizumi A, Tantanapornkul W, Katakami K, Kurabayashi T. Bifid mandibular canals: cone beam computed tomography evaluation. Dentomaxillofacial Radiol. 2010;39(4):235–9.

    Article  Google Scholar 

  5. 5.

    Naitoh M, Nakahara K, Suenaga Y, Gotoh K, Kondo S, Ariji E. variations of the bony canal in the mandibular ramus using cone-beam computed tomography. Oral Radiol. 2010;26(1):36–40.

    Article  Google Scholar 

  6. 6.

    Kong N, Hui M, Miao F, Yuan H, Du Y, Chen N. Mandibular incisive canal in han chinese using cone beam computed tomography. Int J Oral Max Surg. 2016;45(9):1142–6.

    Article  Google Scholar 

  7. 7.

    Han S, Hwang Y. Cone beam Ct findings of retromolar canals in a korean population. Surg Radiol Anat. 2014;36(9):871–6.

    PubMed  Article  Google Scholar 

  8. 8.

    Kawai T, Asaumi R, Sato I, Kumazawa Y, Yosue T. Observation of the retromolar foramen and canal of the mandible: a Cbct and macroscopic study. Oral Radiol. 2012;28(1):10–4.

    Article  Google Scholar 

  9. 9.

    Lizio G, Pelliccioni GA, Ghigi G, Fanelli A, Marchetti C. Radiographic assessment of the mandibular retromolar canal using cone-beam computed tomography. Acta Odontol Scand. 2013;71(3–4):650–5.

    PubMed  Article  Google Scholar 

  10. 10.

    Von Arx T, Hänni A, Sendi P, Buser D, Bornstein MM. Radiographic study of the mandibular retromolar canal: an anatomic structure with clinical importance. J Endod. 2011;37(12):1630–5.

    Article  Google Scholar 

  11. 11.

    Ossenberg NS. Retromolar foramen of the human mandible. Am J Phys Anthropol. 1987;73(1):119–28.

    PubMed  Article  Google Scholar 

  12. 12.

    Schejtman R, Devoto FC, Arias NH. The origin and distribution of the elements of the human mandibular retromolar canal. Arch Oral Biol. 1967;12(11):1261–8.

    PubMed  Article  Google Scholar 

  13. 13.

    Patil S, Matsuda Y, Nakajima K, Araki K, Okano T. Retromolar canals as observed on cone-beam computed tomography: their incidence, course, and characteristics. Oral Surg Oral Med Oral Pathol Oral Radiol. 2013;115(5):692–9.

    PubMed  Article  Google Scholar 

  14. 14.

    Athavale S, Vijaywargia M, Deopujari R, Kotgirwar S. Bony and cadaveric study of retromolar region. People’s J Sci Res. 2013;6(2):14–8.

    Google Scholar 

  15. 15.

    Galdámes IS, Matamala DZ, López MC, Suazo G, Zavando M, Cantín L. Retromolar canal and forame prevalence in dried mandibles and clinical implications. Int J Odontostomatol. 2008;2(2):183–7.

    Google Scholar 

  16. 16.

    Motamedi MH, Gharedaghi J, Mehralizadeh S, Navi F, Badkoobeh A, Valaei N, et al. Anthropomorphic assessment of the retromolar foramen and retromolar nerve: anomaly or variation of normal anatomy? Int J Oral Maxillofacial Surg. 2016;45(2):241–4.

    Article  Google Scholar 

  17. 17.

    Sisman Y, Ercan-Sekerci A, Payveren-Arıkan M, Sahman H. Diagnostic accuracy of cone-beam ct compared with panoramic images in predicting retromolar canal during extraction of impacted mandibular third molars. Med Oral Patol Oral Cir Bucal. 2015;20(1):e74–e81.

    PubMed  Article  Google Scholar 

  18. 18.

    Hepburn D. Some variations in the arrangements of the nerves of the human body. J Anat Physiol. 1887;21(part 3):511–3.

    PubMed  PubMed Central  Google Scholar 

  19. 19.

    Kawai T, Asaumi R, Kumazawa Y, Sato I, Yosue T. Observation of the temporal crest canal in the mandibular ramus by cone beam computed tomography and macroscopic study. Int J Comput Ass Radiol Surg. 2014;9(2):295–9.

    Article  Google Scholar 

  20. 20.

    Ossenberg N. Temporal crest canal: case report and statistics on a rare mandibular variant. Oral Surg Oral Med Oral Pathol. 1986;62(1):10–2.

    PubMed  Article  Google Scholar 

  21. 21.

    Kikuta S, Iwanaga J, Nakamura K, Hino K, Nakamura M, Kusukawa J. The retromolar canals and foramina: radiographic observation and application to oral surgery. Surg Radiol Anat. 2018;40(6):647–52.

    PubMed  Article  Google Scholar 

  22. 22.

    Sawyer DR, Kiely ML. Retromolar foramen: a mandibular variant important to dentistry. J Ann Dent. 1991;50(1):16–8.

    Google Scholar 

Download references


This work was supported in part by a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD, 2018–87). The Project of Invigorating Health Care through Science, Technology and Education (Jiangsu Provincial Medical Youth Talent QNRC2016852), Jiangsu Provincial Medical Innovation Team (CXTDA2017036) and sponsored by Qing Lan Project.

Author information



Corresponding authors

Correspondence to Ruixia Wang or Hua Yuan.

Ethics declarations

Conflict of interest

The authors declare that they have no conflicts of interest.

Ethical approval

All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2008.

Informed consent

Informed consent was obtained from all patients for being included in the study.

Additional information

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Hou, Y., Feng, G., Lin, W. et al. Observation of retromolar canals on cone beam computed tomography. Oral Radiol 36, 365–370 (2020). https://doi.org/10.1007/s11282-019-00414-0

Download citation


  • Cone beam CT(CBCT)
  • Retromolar canal (RMC)
  • Retromolar foramina (RMF)
  • Incidence
  • Oral surgery