International Journal of Anatomical Sciences 2010, 1: 14-16

Research Paper

A Study on the incidence of Retromolar Foramen and Canal in Indian

Dried Human Mandibles and its Clinical Significance

Senthil Kumar S, Kesavi D.

Department of Anatomy, Sri Ramachandra Medical College and Research Institute

Sri Ramachandra University, Chennai 600 116, Tamil Nadu, India.

Key Words: mandible, third molar, retromolar canal & retromolar foramen

 Abstract: The retromolar foramen (RMF) is one of the nonmetrical variants of the mandible (Ossenberg, 1987). The dental practitioners should be aware of this variant and  the possible complications  which  may occur during  anesthetic,  surgical,  and implantation procedures of the mandible .Indian adult dried human mandibles (150) were observed for the presence of retromolar foramen (RMF) or retromolar canal. Their gross morphological features were studied. These canals showed variations in location, length and diameter in relation to third molar.

Many  people   require  removal  of their  third  molar  also  known  as  wisdom teeth. As with any surgical procedure, there are some possible risks and complications (Anderson, 1998). The lower third molar region includes the area in which this tooth, its supporting elements and the adjacent soft parts, the lingual nerve and the elements of the  paralingual  space.  Posterior  to  lower third molar there is a cribose triangular surface, the retromolar triangle and the retromolar  fossa  laterally  (Suazo  et  al.,2007). The cribose area of the retromolar triangle communicates with the mandibular canal, describing it via an anesthetic technique for the inferior alveolar nerve block (Suazo et al., 2008, Sandoval et al.,2008). Clinically, this region is covered by an elevation of mucosa of variable size.

 Correspondance to: Senthil Kumar S, Department of Anatomy,  Sri  Ramachandra  Medical  College  and Research Institute, Sri Ramachandra University Porur, Chennai 600116, India


 Retromolar fossa is a depression where the buccinator muscle is attached above the inferior alveolar canal. From a clinical point of view this area forms, a open corridor for the passage of infections arising in connection with the third molar, this is the so-called Chompret-L’ Hirondel abscess (abcès  migrateur de  Chompret-L’Hirondel) used  it  path  (Libersa  et  al.,  1982;  Peron,2004).  On  the  surface  of  the  retromolar fossa found the retromolar foramen (RMF), which creates a canal of variable depth, regarded as an anatomical variation. Since most   of   the   anatomical   books   do   not mention about this foramen or canal this study was undertaken to analyze the incidence in Indian adult dried mandibles.

 Materials and Methods

 A total of 150 Indian adult dried human mandibles were observed for the presence of retromolar foramen (RMF) or retromolar canal in Department of Anatomy, Sri Ramachandra Medical College and Research  Institute.  Their  locations  in relation to third molar were taken into account for observation. The diameter and the   depth   were   measured   by   using  Mitutoyo’s Dial Caliper.


The retromolar foramen and canal Fig. 1 was found in 26 of 150 mandibles (17.3%) of which 8 on the right side (5.3%),6 on the left side (4%)   and 12 bilaterally (8%)  (Table I). The depth of the retromolar foramen and canal was found to be an average of 12mm Fig.2a and 2b. The diameter  of  the  retromolar  foramen  and canal  was  found  to  be  an  average  of  1.3 mm.  The distance between  posterior third molar to retromolar foramen and canal was found to be an average of 4.5 mm on the right side and 4mm on the left side Fig.3. The distance between anterior border of ramus to retromolar foramen was found to be an average of 8.4 mm on the right side and 8.3mm on the left side. The distance  between lingula to retromolar foramen was found to be an average of 14.1mm on the right side and 12.6mm on the left side.


Table 1 Distribution of Retro Molar  Foramen




Right side Left side Bi- lateral  

























From the above observations the occurrence of RMF was more in females compared to males. The diameter of RMF was found to be larger in the right side. The distance of RMF from third molar, anterior border of ramus  and  lingula  are  also  found  to  be higher on the right side. The bilateral occurrence of RMF was found to be higher in females.

Fig. 1 Photograph showing retromolar  sides.



Fig. 2a Photograph showing the depth of foramen on both retromolar foramen on the right side.


Fig. 2b Photograph showing the measurement retromolar canal.


Fig. 3 Photograph showing retromolar foramen of the depth of on the left side.



The incidence of RMF located in the retromolar fossa, in our study was 17.3%. It is  higher  than  what  reported  earlier  by Suazo, et al., (2008) 12.9% in Brazilians, but lower than what reported by Kodera & Hashimoto, (1995) 19.5% in Japanese population  and  Narayana  et  al.,  (2002) 21.9% in the South Indian population.

 Kodera and Hashimoto (1995) per- formed the dissection of retromolar canal in Japenese cadavers and found within the retromolar canal, the artery running was a branch from the inferior alveolar artery, it ran through the canal forwards and joined with the branches of the buccal artery and the facial artery. The nerve in the retromolar canal  was  a  branch  from  the  trunk  of inferior alveolar nerve and branched off to the following areas: the third mandibular molar,  the  mucosa  of  retromolar  triangle, the buccal mucosa, and the buccal gingiva of   the   mandibular   premolar   and   molar region. These elements may be injured in the dieresis procedures, flap lifting, bone tissue for autologous bonegrafts, osteotomy for the surgical extraction of lower third molars, placement of osseointegrated implants for orthodontic or during the division of the mandibular ramus in the sagittal split osteotomy surgery (Reyneke et al., 2002 , Boronat Lopez and Peñarrocha Diago, 2006).

 This study clearly establishes the incidence of the retromolar foramen and its clinical  significance.  The  retromolar foramen is highly variable in their morphology and morphometry. The cortical plate  over  the  retromolar  triangle  is  not heavy as the bone surrounding it and it is more cancellous (Ash et al., 2003). During routine anesthetic, surgical and implantation procedures of the mandible, care should be taken not to damage the neurovascular bundle passing through the retromolar foramen.

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