Anatomy Research International

Anatomy Research International / 2014 / Article

Research Article | Open Access

Volume 2014 |Article ID 296717 |

Bhagath Kumar Potu, Vinod Kumar, Abdel-Halim Salem, Marwan Abu-Hijleh, "Occurrence of the Retromolar Foramen in Dry Mandibles of South-Eastern Part of India: A Morphological Study with Review of the Literature", Anatomy Research International, vol. 2014, Article ID 296717, 5 pages, 2014.

Occurrence of the Retromolar Foramen in Dry Mandibles of South-Eastern Part of India: A Morphological Study with Review of the Literature

Academic Editor: Levent Sarikcioglu
Received24 Jun 2014
Accepted31 Aug 2014
Published29 Sep 2014


The retromolar foramen (RMF) is a rare anatomical structure situated in the retromolar fossa behind the third molar tooth. When it is present, the foramen is connected with the mandibular canal and is believed to transmit neurovascular structures that provide accessory source to the mandibular molars and the buccal area. Reports from the literature show that the presence of RMF could pose a challenge in complete blockage of the inferior alveolar nerve during mandibular surgeries. We report the incidence of retromolar foramen from ninety-four dry mandibles of south-eastern part of Karnataka State, India. The foramen was observed in 11 mandibles out of 94 included in the study (11.7%). In three mandibles, the foramen was present bilaterally (3.2%) and in three it was on the left side (3.2%) and in five it was on the right side (5.3%). For the first time, we also measured the dimensions of the retromolar area and distance of the foramen from third molar tooth to understand its risks during the surgical extraction of the lower third molar tooth. A thorough review of the literature has also been done to compare the present findings with the studies reported from the various populations.

1. Introduction

The RMF is an inconstant foramen situated in the central portion of the retromolar fossa which is bounded by the anterior border of ramus of the mandible and temporal crest. The foramen receives a canal of variable depth that normally arises from the mandibular canal behind the lower third molar, which is regarded as the retromolar canal (RMC) [1]. Normal morphological findings of the human mandible and its possible variations that occur have attracted special interest in the recent years in the field of odontostomatological surgeries [2]. One such anatomical variation which draws special attention in clinical dental practice is the RMF in the retromolar trigone (RMT). The trigone is bounded medially by temporal crest, laterally by the anterior border of the ramus, and anteriorly by the base of third molar tooth [3]. The RMF has generally been neglected in anatomical text books and this has been rarely studied or reviewed in the dental literature. The frequency of RMF has been reported in different populations showing a wide varying incidence between 3.2% and 72% [420]. However, there is no recent systematic study conducted on the RMF occurrence in the south-eastern part of Karnataka, India, with the morphometry we adopted; hence we report our findings on the occurrence of RMF in this population.

2. Material and Methods

In this study, all available 94 dry, fully ossified adult mandibles from the Department of Anatomy, Sapthagiri Institute of Medical Sciences and Research Center, Bangalore, south-eastern part of India, were included. In 94 dry mandibles, the presence of RMF was noted and the lengths of the anterior, medial, and lateral boundaries of the retromolar trigone were carefully measured using a digital vernier caliper. Wherever foramina were noticed, the distance of the RMF from the posterior border of socket for third molar, anterior border of the ramus, and lingula were also measured, respectively. All the measurements were performed independently by two individuals (Bhagath Kumar Potu and Vinod Kumar) for three times and averaged to arrive at accurate data. The mean, range, and standard deviation of all the measurements were statistically analyzed.

3. Results

Retromolar foramen (RMF) was observed in 11 mandibles out of 94 included in the study (11.7%). In three mandibles, the foramen was observed bilaterally (3.2%) and in another three it was on the left side (3.2%) and in another five it was on the right side (5.3%). It was found that the length of medial boundary of the retromolar trigone varies between 19 and 30 mm, the lateral boundary varies between 21 and 32 mm, and the anterior boundary varies between 9 and 16 mm (Table 1). The RMF in our study was mostly located in medial aspect of the retromolar fossa close to lingula (Figure 1). The distances of the RMF from the posterior border of socket for third molar, anterior border of the ramus, and lingula are shown in Table 2. It was seen that the distance of RMF from third molar socket, from the anterior border of ramus, and also from the lingula varies between 4 and 11 mm, 3 and 11 mm, and 2 and 8 mm, respectively. The incidence of the RMF in our study is also compared with the studies conducted so far in different populations reported in the literature (Table 3).

Mandible number with RMFSide Borders of the retromolar trigone (mm)

26Left 353516
32Right 293210
48Left 464112
58Right 434611
64Right 423815
72Right 433814
80Right 343512
88Right 343012
88Left 303213
91Right 373512
91Left 363510

Mean ± SD 37.14 ± 5.2336.36 ± 4.1312.29 ± 1.98


Mandible numberSide examinedDistance between the retromolar foramen and
3rd molar socket (mm)Ant. border of ramus (mm)Lingula (mm)

26Left 7106
32Right 836
48Left 1136
58Right 882
64Right 6114
72Right 492
80Right 895
88Right 586
88Left 594
91Right 643
91Left 545

Mean ± SD6.21 ± 2.016.57 ± 2.824.43 ± 1.87


AuthorYear of studyNumber of mandibles studiedPresence of retromolar foramen (%)Population of the study

Schejtman et al. [4]19671813 (72)Argentine aborigines
Ossenberg [5]1987867 (8.1)Italian
943 (3.2)Japanese
48540 (8.2)Eskimos
111 (9.1)Canadians of European descent
Sawyer and Kiely [6]199123418 (7.7)American
Kodera and Hashimoto [15]1995418 (20)Japanese
Pyle et al. [7]199947537 (7.8)Caucasian (n = 226)
Afro-American (n = 249)
Narayana et al. [8]200224253 (21.9)Indian
Priya and Manjunath. [9]200515720 (12.7)Indian
Lagrana et al. [16]2006509 (18) Argentinean
Bilecenoglu and Tuncer [10]20064010 (25)Turkish
Suazo et al. [11]200829438 (12.9)Brazilian
von Arx et al. [12] 201112131 (25.6)Swiss
Kawai et al. [13]20124624 (52)Japanese
Rossi et al. [14]201222259 (26.6)Brazilian
Lizio et al. [18]2013233 (hemimandibles)34 (14.6)Italian
Athavale et al. [19]20137110 (14.1)Indian
Orhan et al. [20]201312614 (11.1)Turkish
Our study 20149411 (11.7)Indian

4. Discussion

Considering the wide variation of incidence and the importance of this region in dental surgical procedures, the present study documented the prevalence of retromolar foramen in dry mandibles of a south-eastern Indian population sample. Percentage of the retromolar foramen occurrence in our study falls somewhere within the ranges reported from other Indian [9, 19], Turkish [20], Italian [18], Canadians of European descent [5], and Brazilian [11] populations (See Table 3). It has been observed that the neurovascular bundle of the RMF originated in the mandibular canal and penetrated into distal lamina dura of the distal root of the third molar [4]. Dentists in particular should be aware of this accessory innervation provided by RMF in the endodontic treatment [21]. Our findings show that the distance between the 3rd molar and RMF is being within the short range of 4–11 mm which is comparable with the recent reports published in the literature [8, 9, 19]. This close relation of RMF with 3rd molar could lead to damage of the structures traversing through RMF during the third molar extraction and could be a reason for postoperative hematomas as described by previous authors due to rupturing of the vessels in RMF [2225]. The incidences reported from Indian population [8, 9, 19] are varying from 12 to 22%. The differences in the incidence of the RMF in these studies could be related to the differential origins of the Indian population. The presence of RMF with additional sensory nerve fibers was first reported by Sutton in 1974 [26]. He related the presence of this foramen to the failure of obtaining analgesia using classical anesthetic techniques [26]. Thus, the studies of the incidence of RMF are important in order to avoid failure in regional anesthetic techniques for blocking the inferior alveolar nerve and buccal nerve fibers [15, 27].

Singh reported that, during surgery of a third molar, he injured a nerve that crossed an unusual foramen located in the retromolar fossa [28]. After the surgery, it was found that the patient presented with paresthesia of the buccal mucosa from the retromolar region to the canine on the operated side. When this postoperative complication was investigated further, it was found that the nerve injured was a branch of the buccal nerve which crossed the RMF [28]. Anderson et al. [29] confirmed that the components in the RMF and canal are the nerves that provide innervation to the pulp of third molar, retromolar region and to the fibers of the temporalis and buccinator muscles. Thus damage to nerves of RMF and canal will disrupt the functions of temporalis and buccinator muscles. Pinsolle et al. [30] suggested that, because the RMF also allows the passage of vascular components, this may facilitate the spread of infection and metastases from the oropharynx to the blood circulation.

Keeping our measurements and observations in mind, one should be cautious when performing the following dental surgeries: third molar extraction, sagittal split osteotomies of the mandible, dieresis procedures, flap lifting, and placement of osseo-integrated implants [31].

5. Conclusion

This study reports the incidence of RMF in south-eastern part of Karnataka State, Indian sample, to form a basis for future better understanding of clinical and surgical practice related to the retromolar area. The RMF has great importance in the odontostomatological practice due to the prevalence of the pathological processes and complications related to the retromolar area involved in the practice. This could be the reason why this area is subject of a great number of surgical procedures. Knowledge of the location and contents of RMF should be carefully considered for choosing the best plan and consequently for optimizing anesthetic and surgery procedure during oral and maxillofacial procedures. We hope that this study would especially help surgeons in this part of the world to understand this area better. However, we declare that we had no availability of the radiological techniques for this present research investigations and this could be the limitation of our study. Our observations may alert the dental surgeons to conduct further studies and also to compare with studies of larger populations across the world to understand its origin and evolutionary importance.

Conflict of Interests

The authors declare that there is no conflict of interests regarding the publication of this paper.


  1. B. Kumar Potu, S. Jagadeesan, K. Mr Bhat, and S. Rao Sirasanagandla, “Retromolar foramen and canal: a comprehensive review on its anatomy and clinical applications,” Morphologie, vol. 97, no. 317, pp. 31–37, 2013. View at: Publisher Site | Google Scholar
  2. V. Claeys and G. Wackens, “Bifid mandibular canal: Literature review and case report,” Dentomaxillofacial Radiology, vol. 34, no. 1, pp. 55–58, 2005. View at: Publisher Site | Google Scholar
  3. B. K. B. Berkovitz, “Skull and mandible,” in Grays Anatomy: The Anatomical Basis of Clinical Practices, S. Standring, H. Ellis, J. C. Healy, D. Jhonson, and A. Williams, Eds., p. 482, Churchill Livingstone, New York, NY, USA, 39th edition, 2005. View at: Google Scholar
  4. R. Schejtman, F. C. H. Devoto, and N. H. Arias, “The origin and distribution of the elements of the human mandibular retromolar canal,” Archives of Oral Biology, vol. 12, no. 11, pp. 1261–1267, 1967. View at: Publisher Site | Google Scholar
  5. N. S. Ossenberg, “Retromolar foramen of the human mandible,” American Journal of Physical Anthropology, vol. 73, no. 1, pp. 119–128, 1987. View at: Publisher Site | Google Scholar
  6. D. R. Sawyer and M. L. Kiely, “Retromolar foramen: a mandibular variant important to dentistry,” Annals of Dentistry, vol. 50, no. 1, pp. 16–18, 1991. View at: Google Scholar
  7. M. A. Pyle, T. R. Jasinevicius, J. A. Lalumandier, K. J. Kohrs, and D. R. Sawyer, “Prevalence and implications of accessory retromolar foramina in clinical dentistry,” General Dentistry, vol. 47, no. 5, pp. 500–504, 1999. View at: Google Scholar
  8. K. Narayana, U. A. Nayak, W. N. Ahmed, J. G. Bhat, and B. A. Devaiah, “The retromolar foramen and canal in South Indian dry mandibles,” European Journal of Anatomy, vol. 6, no. 3, pp. 141–146, 2002. View at: Google Scholar
  9. R. Priya and K. Y. Manjunath, “Retromolar foramen,” Indian Journal of Dental Research: Official Publication of Indian Society for Dental Research, vol. 16, no. 1, pp. 15–16, 2005. View at: Google Scholar
  10. B. Bilecenoglu and N. Tuncer, “Clinical and Anatomical Study of Retromolar Foramen and Canal,” Journal of Oral and Maxillofacial Surgery, vol. 64, no. 10, pp. 1493–1497, 2006. View at: Publisher Site | Google Scholar
  11. G. Suazo, M. Zavando, and L. Cantín, “Retromolar canal and foramen prevalence in dried mandibles and clinical implications,” International Journal of Odontostomat, vol. 2, no. 2, pp. 183–187, 2008. View at: Google Scholar
  12. T. Von Arx, A. Hänni, P. Sendi, D. Buser, and M. M. Bornstein, “Radiographic study of the mandibular retromolar canal: an anatomic structure with clinical importance,” Journal of Endodontics, vol. 37, no. 12, pp. 1630–1635, 2011. View at: Publisher Site | Google Scholar
  13. T. Kawai, R. Asaumi, I. Sato, Y. Kumazawa, and T. Yosue, “Observation of the retromolar foramen and canal of the mandible: a CBCT and macroscopic study,” Oral Radiology, vol. 28, no. 1, pp. 10–14, 2012. View at: Publisher Site | Google Scholar
  14. A. C. Rossi, A. R. Freire, G. B. Prado, F. B. Prado, P. R. Botacin, and P. H. Ferreira Caria, “Incidence of retromolar foramen in human mandibles: Ethnic and clinical aspects,” International Journal of Morphology, vol. 30, no. 3, pp. 1074–1078, 2012. View at: Publisher Site | Google Scholar
  15. H. Kodera and I. Hashimoto, “A case of mandibular retromolar canal: elements of nerves and arteries in this canal,” Kaibogaku Zasshi, vol. 70, no. 1, pp. 23–30, 1995. View at: Google Scholar
  16. R. Lagraña, M. Frank, M. Camacho, F. Gauna, and M. Abalo, Forámenes Accesorios del Hueso Mandibular Humano, Cátedra de Anatomía General, Facultad de Odontología Universidad Nacional del Nordeste, 2006.
  17. J. Motta Junior, F. Maria de Lourdes, R. A. Matheus, and G. A. V. Stabile, “Forame retromolar: sua repercussão clínica e avaliação de 35 mandíbulas secas,” Revista de Odontologia da UNESP, vol. 41, no. 3, pp. 164–168, 2012. View at: Google Scholar
  18. G. Lizio, G. A. Pelliccioni, G. Ghigi, A. Fanelli, and C. Marchetti, “Radiographic assessment of the mandibular retromolar canal using cone-beam computed tomography,” Acta Odontologica Scandinavica, vol. 71, no. 3-4, pp. 650–655, 2013. View at: Publisher Site | Google Scholar
  19. S. A. Athavale, M. Vijaywargia, R. Deopujari, and S. Kotgirwar, “Bony and cadaveric study of retromolar region,” People's Journal of Scientific Research, vol. 6, no. 2, pp. 14–18, 2013. View at: Google Scholar
  20. A. I. Orhan, K. Orhan, S. Aksoy et al., “Evaluation of perimandibular neurovascularization with accessory mental foramina using cone-beam computed tomography in children,” Journal of Craniofacial Surgery, vol. 24, no. 4, pp. e365–e369, 2013. View at: Publisher Site | Google Scholar
  21. M. C. Madeira, Anatomia do Dente, Sarvier, São Paulo, Brazil, 6th edition, 2010.
  22. B. Azaz and J. Lustmann, “Anatomical configurations in dry mandibles,” British Journal of Oral Surgery, vol. 11, no. 1, pp. 1–9, 1973. View at: Publisher Site | Google Scholar
  23. G. J. Petruzzelli, F. K. Knight, D. Vandevender, J. I. Clark, and B. Emami, “Posterior marginal mandibulectomy in the management of cancer of the oral cavity and oropharynx,” Otolaryngology—Head and Neck Surgery, vol. 129, no. 6, pp. 713–719, 2003. View at: Publisher Site | Google Scholar
  24. T. Muto and M. Kanazawa, “Mandibular reconstruction using the anterior part of ascending ramus: report of two cases,” Journal of Oral and Maxillofacial Surgery, vol. 55, no. 10, pp. 1152–1156, 1997. View at: Publisher Site | Google Scholar
  25. I. S. Galdames, “Lower third molar region,” International Journal of Morphology, vol. 30, no. 3, pp. 970–978, 2012. View at: Publisher Site | Google Scholar
  26. R. N. Sutton, “The practical significance of mandibular accessory foramina,” Australian Dental Journal, vol. 19, no. 3, pp. 167–173, 1974. View at: Publisher Site | Google Scholar
  27. E. Kaufman, N. J. Serman, and P. D. Wang, “Bilateral mandibular accessory foramina and canals: a case report and review of the literature,” Dentomaxillofacial Radiology, vol. 29, no. 3, pp. 170–175, 2000. View at: Publisher Site | Google Scholar
  28. S. Singh, “Aberrant buccal nerve encountered at third molar surgery,” Oral Surgery Oral Medicine and Oral Pathology, vol. 52, no. 2, p. 142, 1981. View at: Publisher Site | Google Scholar
  29. L. C. Anderson, T. F. Kosinski, and P. J. Mentag, “A review of the intraosseous course of the nerves of the mandible,” The Journal of oral Implantology, vol. 17, no. 4, pp. 394–403, 1991. View at: Google Scholar
  30. V. Pinsolle, Y. Truilhe, C. Majoufre, V. Michelet, and J. Pinsolle, “Posterior marginal mandibulectomy for cancer of the oral cavity and oropharynx. An experience of 14 clinical cases,” Annales de Chirurgie Plastique et Esthetique, vol. 42, no. 3, pp. 223–227, 1997. View at: Google Scholar
  31. J. P. Reyneke, P. Tsakiris, and P. Becker, “Age as a factor in the complication rate after removal of unerupted/impacted third molars at the time of mandibular sagittal split osteotomy,” Journal of Oral and Maxillofacial Surgery, vol. 60, no. 6, pp. 654–659, 2002. View at: Publisher Site | Google Scholar

Copyright © 2014 Bhagath Kumar Potu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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