Year : 2009 | Volume
: 20 | Issue : 2 | Page : 150--152
Radiographic evaluation of the mental foramen in a selected Iranian population
Sina Haghanifar1, Mehrak Rokouei2,
1 Department of Oral and Maxillofacial Radiology, Dental Faculty, Babol University of Medical Sciences, Babol, Iran
2 Private Practice, Babol, Iran
Department of Oral and Maxillofacial Radiology, Dental Faculty, Babol University of Medical Sciences, Babol
Background: Information on the position of the mental foramen is important for dental surgeons. Variations in its position can be a cause of complications during local anesthesia or surgical procedures. The usual position of the mental foramen in an Iranian population has not been previously reported.
Aims: The purpose of this study was to determine the most common location of the mental foramen in an Iranian population. We also analyzed gender differences and the symmetry of location within individuals.
Materials and Methods : 400 panoramic radiographs were evaluated with regard to the location and symmetry of the mental foramina in male and female subjects.
Results : We found that the mental foramen was located between the first and second premolars in 47.2% of patients and in line with the second premolar in 46%. In 49.2% of males, the mental foramen was in line with the second premolar. In 50.9% of females it was between the first and second premolars. It was symmetrical in 85.7%.
Conclusions : Based on this study it appears that the most common position of mental foramen is either between the two premolars or in line with the second premolar. This is in concordance with previous studies.
|How to cite this article:|
Haghanifar S, Rokouei M. Radiographic evaluation of the mental foramen in a selected Iranian population.Indian J Dent Res 2009;20:150-152
|How to cite this URL:|
Haghanifar S, Rokouei M. Radiographic evaluation of the mental foramen in a selected Iranian population. Indian J Dent Res [serial online] 2009 [cited 2013 Dec 11 ];20:150-152
Available from: http://www.ijdr.in/text.asp?2009/20/2/150/52886
The mental foramen on each side is located on the buccal cortex of the mandibular bone and lies near the apices of the premolars. It has been shown to be located at precisely the same level on most humans (13-15 mm superior to the inferior border of the mandible). The opening of the mental foramen is directed outward, upward, and posteriorly, viewed from inside out. It transmits the mental vessels and nerve.  The mental nerve is a terminal branch of the inferior alveolar nerve; it supplies sensory innervation to the lower lip, the buccal vestibule, and the gingiva mesial to the first mandibular molar.  The mental bundle can be traumatized during surgical procedures, resulting in paresthesia or anesthesia in the area innervated by the nerve. Additionally, local anesthesia of the terminal incisive branches of the inferior alveolar nerve and the mental nerve can be achieved if the mental canal is accurately located and anesthetic solution deposited within it. Thus, accurate information regarding the location and orientation of the mental canal and its foramen can be very important. 
As the bone density increases, the mental foramen becomes more difficult to identify on radiographs.  Such cases, in which the mental foramen cannot be identified on panoramic radiographs under ordinary exposure and viewing conditions, were classified as 'unidentified type' by Yosue and Brooks. ,
The location of mental foramen has been studied in different populations. ,,,,,,,,,,,, The purpose of this study was to report the usual position of the mental foramen in Iranians; it has not been reported in this population before.
Materials and Methods
We evaluated 400 panoramic radiographs of patients who had been referred to our Dentomaxillofacial Radiology Center in Babol city (in Iran) during two years. All panoramic radiographs were taken by Planmeca 2002EC (tube potential: 60-80 KV, tube current: 4-12 mA, total filtration: 2.5 mmAl, focal spot: 0.3, and time: 18 s) and had high-quality processing. Exclusion criteria were:
Presence of a radiolucent lesion in the lower jaw anywhere in the area extending from the right first molar to the left first molarPresence of a missing tooth in the lower jaw (between 36 and 46)Nonvisualization of the mental foramen bilaterallyIncomplete eruption of permanent teethPatient under 18 yearsPresence of periodontal lesionsPatient with previous orthodontic treatmentPresence of crowding and spacing in the lower arch
The position of the image of the mental foramen was recorded as follows:
Position 1: Situated anterior to the first premolar
Position 2: In line with the first premolar
Position 3: Between the first and second premolars
Position 4: In line with the second premolar
Position 5: Between the second premolar and first molar
Position 6: In line with the first molar
We used the edge of a ruler to identify the longitudinal axis of the nearest tooth and the position of the mental foramen was recorded in relation to this. If the mental foramen was too large or was situated between two teeth, the position of the foramen was established after drawing an imaginary line parallel to the long axis of the teeth.  After evaluation of each panoramic radiograph, the location of the mental foramen on each side was recorded in the form. The location of the mental foramen was reported on the basis of gender and symmetry or asymmetry.
Of the 400 panoramic radiographs analyzed, 178 were that of males and 222 that of females. The most common position for the mental foramen in this sample was position 3 (47.2%). There was no case found in position 1 (anterior to the first premolar). On the right side, the commonest position of the mental foramen was position 3 (24.7%) and on the left side it was position 4 (23.6%) [Table 1]. Position 4 was the most common one among males (49.2%) and position 3 was the most common one among females (50.9%) [Table 2].
In 343 cases (85.7%) the mental foramina were symmetrically located. For the symmetrically placed mental foramina, the most common location was position 3 (41.5%), followed by position 4 (39.8%). No case was found in position 1 and 6. No statistically significant differences were seen between males and females in symmetry and asymmetry location of mental foramen in both sides. P  in a North American white population and by Fishel et al.  and Olasoji et al.  in Northern Nigerian adults showed that the most common location of the mental foramen was between the two premolars. These findings are consistent with our results. But studies done in other populations such as Malays, Asian Indians, Kenyan Africans, and Saudis, as well as the studies done by Phillips et al., have indicated that the mental foramen is most commonly positioned in line with the second premolar tooth. ,,,,,,,
In our review of literature we found that according to most authors the mental foramen is usually located between the lower premolars. ,, However, there were some studies that reported that it most commonly lies near the apex of the second premolar. ,,, Other studies have found that both locations are common. ,
In this study we used panoramic radiographs because the mental foramen is seen more consistently on the wide field of mandible view in panoramic radiographs than on periapical radiographs. 
We selected patients over the age of 18 because we needed patients with completed skeletal growth. The presence of periodontal lesions and also previous orthodontic treatment could cause tooth migration; we, therefore, omitted these cases from our study.
In conclusion, the most common locations of the mental foramen are between the two premolars and in line with the second premolar (below and/or mesial to the second premolar). This agrees with the results of previous studies in other populations. The mental foramina are usually symmetrically located on both sides.
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