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 Table of Contents  
ORIGINAL ARTICLE
Year : 2016  |  Volume : 28  |  Issue : 1  |  Page : 11-16

Radiographic location of mental foramen in a randomly selected population of Maharashtra


1 Department of Oral Medicine and Radiology, Krishna Institute of Medical Sciences Deemed University, Karad, Maharashtra, India
2 Department of Periodontology, Krishna Institute of Medical Sciences Deemed University, Karad, Maharashtra, India
3 Department of Public Health Dentistry, School of Dental Sciences, Krishna Institute of Medical Sciences Deemed University, Karad, Maharashtra, India

Date of Web Publication8-Sep-2016

Correspondence Address:
Ashwinirani Suragimath
Department of Oral Medicine and Radiology, School of Dental Sciences, Krishna Institute of Medical Sciences Deemed University, Karad, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0972-1363.189989

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   Abstract 

Introduction: Mental foramen is usually the anterior limit of inferior dental canal, which is located in the body of mandible between the inferior and alveolar margins. The accurate identification of the position of the mental foramen is important for both diagnostic and clinical procedures on the mandible. Objectives: To determine the most common type and position of the mental foramen in a selected population of Maharashtra. Materials and Methods: A total of 448 orthopantomographs showing mental foramen bilaterally were considered for this study. The type, position, and symmetry of mental foramen on contralateral sides were noted in both the gender. Frequency and percentage of type, position, and symmetry of mental foramen were calculated statistically. Results: The majority of mental foramen were of separate type (n = 554, 61.8%) followed by the continuous type (n = 342, 38.2%). The most common position of the mental foramen was position 4 (n = 554, 61.8%) followed by position 3 (n = 289, 32.2%). The mental foramen were bilaterally symmetrical (n = 246, 54.9%) and asymmetrical (n = 202, 45.1%) in radiographs. Significant differences were observed in position between the right and left side in both the gender. Conclusion: The separate type of mental foramen was most predominant and the most common location was position 4 followed by position 3.

Keywords: Continuous type, mental foramen, orthopantomograph, separate type


How to cite this article:
Suragimath A, Suragimath G, Murlasiddiah SK. Radiographic location of mental foramen in a randomly selected population of Maharashtra. J Indian Acad Oral Med Radiol 2016;28:11-6

How to cite this URL:
Suragimath A, Suragimath G, Murlasiddiah SK. Radiographic location of mental foramen in a randomly selected population of Maharashtra. J Indian Acad Oral Med Radiol [serial online] 2016 [cited 2022 Oct 3];28:11-6. Available from: https://www.jiaomr.in/text.asp?2016/28/1/11/189989


   Introduction Top


Mental foramen (MF) is usually the anterior limit of inferior dental canal, which is located in the body of mandible between the inferior and alveolar margins. Mental nerve passes through the MF and supplies the chin, lower lip, lower incisors, canines, and premolars. Damage to the mental nerve can result when the nerve gets stretched, compressed, and partially or totally transected. The complications of damage may result in paraesthesia, hypoesthesia, dysthesia, and anesthesia of the teeth, lower lip, or surrounding skin and mucosa. Identifying the correct location of MF is important for the dentist during various operative procedures such as endodontics, placement of dental implants, periapical surgeries, periodontal surgeries, and orthognathic surgeries. In general, the MF is difficult to locate because of a lack of consistent anatomical landmarks for reference and the foramen cannot be clinically visualized or palpated.[1]Radiographically, MF appears as either round, oblong, slit-like, or very irregular radiolucent area which is partially or completely corticated. MF may be located anywhere between the root of canine to mesial root of the mandibular first molar. Differentiating MF from periapical pathologies is sometimes difficult radiographically when it is projected over the premolar roots. The type and location of MF can be well-appreciated on orthopantomographs (OPG) bilaterally.[2] OPG provides the ability to view the entire body of the mandible and allows for a more accurate location of the MF in both horizontal as well as in vertical dimensions.[3]

In 2005, Agthong et al. analyzed the position of the MF in several populations using OPG.[4] In 1989, Yosue and Brooks studied the types of MF on OPG and classified them into four types, namely, continuous type, separate type, diffuse type, and unidentified type.[5],[6] Most studies and textbooks describe the common location of MF as either below the apex of the second premolar or in between the apices of the first and second premolar. Variations in the position and shape of the MF have been reported in different ethnicity.[7],[8],[9] There is sparse data available on the type and position of MF in Maharashtra population. The present study was designed to determine the type, position, and symmetry of MF in Maharashtra population.


   Materials and Methods Top


A total of 500 participants in the age group between 18 and 50 years undergoing conventional OPG were considered for the study from the Department of Oral Medicine and Radiology. The subjects were undergoing OPG for diagnostic, periodontal, surgical, or orthodontic purposes. The study participants were explained about the objectives of the study and an informed consent was obtained before enrolling them in the study. All OPGs were captured using Xtropan 2000 system (Xtronics Imaging Systems, Mumbai, India, tube potential: 50–85 kV, tube current: 12 mA and time: 14 s) using Carestream (T-Mat GIRA) films. The magnification factor reported by the manufacturer was 1.2.

Inclusion criteria

  • Patients over 18 years of age
  • High quality radiographs with respect to angulation and contrast
  • Dentate patients, especially with erupted mandibular premolars and first molars.


Exclusion criteria

  • Patients with drifted, crowded, spaced, or rotated lower teeth
  • Patients with previous history of orthodontic treatment
  • Missing teeth in mandibular premolars and first molar regions
  • Radiographs showing radiolucent or radiopaque lesions in the mandibular premolars, canine, and first molar region
  • Radiographs of low contrast and quality
  • Patients with supernumerary teeth in the premolar and molar regions
  • Radiographs showing magnification and artifacts.


Out of 500 OPGs, only 448 (215 males and 233 females) were considered because 52 radiographs did not meet the inclusion criteria. The study was conducted during the period from July 2013 to March 2014 after obtaining the institutional ethical clearance. OPGs were observed by a single Oral Medicine and Radiologist with help of an X-ray viewer. Intraobserver variability was reproducible more than 90%. The types of MF were classified according to Yosue and Brooks classification. When multiple foramina were seen, the true radiographic MF was considered to be the uppermost one, nearest to the mandibular canal [Figure 1] and [Figure 2].
Figure 1: Panoramic radiograph showing separate type of MF bilaterally

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Figure 2: Panoramic radiograph showing continuous type of MF bilaterally

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Yosue and Brooks classification:[5],[6]

Type I: Continuous type, the mental canal is continuous with the mandibular canal

Type II: Separate type, the foramen is distinctly separated from the mandibular canal and appears as a well-defined radiolucency with a distinct border

Type III: Diffuse type, the foramen has an indistinct border

Type IV: Unidentified type, the foramen cannot be seen.

After locating the MF, lines were drawn along the longitudinal axis of teeth using a marker pen on the OPGs. The position of MF was recorded in relation to these lines, as explained by Anshuman et al.[10] The position of MF was classified according to Tebo and Telford classification.[11] The OPGs were also analyzed to check whether MF was symmetrical or asymmetrical bilaterally in both the gender [Figure 3] and [Figure 4].
Figure 3: Panoramic radiograph showing bilateral position 4 MF

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Figure 4: Panoramic radiograph showing asymmetrical position of MF, right side position 3, and left side position 4

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Tebo and Telford classification:[11]

Position 1: The foramen that lay on a longitudinal axis which passed between the canine and the first premolar

Position 2: The foramen that lay on the longitudinal axis of the first premolar

Position 3: The foramen that lay on the longitudinal axis which passed between the first and second premolars

Position 4: The foramen that lay on the longitudinal axis of the second premolar

Position 5: The foramen that lay on the longitudinal axis which passed between the second premolar and the first molar

Position 6: The foramen that lay on the longitudinal axis of the first molar.

The data obtained was entered in an MS excel sheet. Type, frequency, and percentages were calculated. The differences in both sides in gender were calculated using two-tailed unpaired t-test.


   Results Top


Out of 448 OPGs (896 MF) observed, 215 were of males and 233 were of females. Separate type of MF was observed in 61.8% (554), followed by continuous type in 38.2% (342). The most common position of the MF was position 4 (61.8%) followed by position 3 (32.2%), position 5 (3.2%), and position 2 (2.6%). There were no OPGs with position 1 and position 6 in our study participants [Table 1]. In males, the percentage of Position 4 was more on right side than on the left side followed by position 3 with significant differences between right and left sides in relation to position 2, position 3, position 4, and position 5 [Table 2]. In females, the percentage of Position 4 was more on the right side than on the left side followed by position 3, which was more on the left side than the right. Significant differences were observed between right and left sides in relation to position 2, position 3, position 4, and position 5 [Table 3]. The MF was bilaterally symmetrical in 54.9% (n = 246) of cases and asymmetrical in 45.1% (n = 202) of cases [Table 4].
Table 1: Position of the MF in horizontal relation to the apices of teeth on the OPGs of 448 Indian subjects (n=896)

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Table 2: Position of MF in horizontal relation to the apices of teeth on the OPGs of 215 male subjects (n=430)

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Table 3: Position of MF in horizontal relation to the apices of teeth on the OPGs of 233 female subjects (n=466)

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Table 4: Distribution of symmetrical and asymmetrical position of MF

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   Discussion Top


The accurate identification of position of the MF is important for both diagnostic and clinical procedures of the mandible. In children, before tooth eruption, MF is closer to the superior margin of the body of the mandible, and during the eruption period, MF descends to halfway between the superior and inferior margins of the body of the mandible; in adults, with the teeth preserved, the MF is closer to the inferior border of the body of the mandible. During old age, when the alveolar bone resorption starts, the MF is placed near to the superior border of the mandible, and in severe cases of resorption, the MF and adjacent part of the mandibular canal are open at the superior margin of the body of the mandible.[12]

Previous studies conducted to study the position, size, and shape of MF on the dry mandible have shown a close correlation with the radiographic location of the MF.[5],[7] Radiologically, intraoral periapical radiographs, OPGs, cephalometric radiographs, conventional tomograph, and computed tomograph are used to locate MF. In the present study, OPGs were used because they are more accurate in the localization of MF in both the horizontal and vertical dimensions bilaterally. A study conducted by Santini and Land et al. reported that, in Chinese population, the MF was in line with second premolar, and in British people, between first and second premolars.[8] The studies conducted on different races have reported that MF is positioned more posteriorly in Blacks than in Whites.[13]

In our study, the most common position of MF was position 4 followed by position 3 in both the genders. The results are in accordance with other studies.[9],[14],[15],[16],[17],[18],[19],[20],[21] Santini and Alayan [22] conducted an anthropometric study on the position of the MF based on evaluation of 76 Chinese, 46 European, and 33 Indian skulls. The modal position of the foramen in the Chinese samples was position 4 (in line with the long axis of the second premolar), whereas among Europeans and Indians it was position 3 (in between the first and second premolar). They concluded that population-based differences occur in the position of MF. Studies by Udhaya et al. and Rastogi et al. on dry skull found 51.5% and 53% of position 4, respectively, which was lesser than our study; this may be due to the small sample size in the previous studies.[15],[19]

A morphometric study on the analysis of MF in human mandibles of south Gujarat by Agarwal and Gupta found that the most common position was position 4, which accounts for 81.5% on both the right and left sides. The percentage of position 4 was higher in their study compared to our study.[9] The studies by Shankland on Asian Indians and Gupta done in India showed that the most common position was position 4, which accounted for 75.4% and 75.8%, respectively.[20],[21] The results of our study in relation to position was also in accordance with the studies done in different populations of the world like the Ngeow and Yuzuwati studies done in Malaysian population,[16] Nanayakkara study conducted in SriLanka,[23] Wang et al. study conducted in Chinese,[24] and Kim et al. study conducted in Korean populations,[25] and Apinhasmit et al. in Thai population.[26]

The results of the present study regarding the position of MF were contradictory to the studies of Rupesh et al. conducted in Asian Indians,[27] Anshuman et al. conducted in Jaipur population,[10] Shah et al.,[28] in Gujarat population, and Haghanifer et al.[29] in Iranian population, where position 3 was most common followed by position 4. Comparison of position of MF on the right and left side showed significant differences in both the gender for position 2, position 3, position 4, and position 5. As per our knowledge, till now no study has compared between right and left sides. In general, the overall percentage of position 4 and position 3 accounts for 80–95%. The overall percentage in the present study was 94.6%, which was similar to the study conducted by Haghanifer et al.[29] on Iranian population, where they found it to be 93.2%.

The most frequent type of MF in the present study was separate type (61.8%) followed by continuous type (38.2%), which is in accordance with the study conducted by Shah et al. in Gujarat population.[28] In both the males and females and on both sides, the separate type was the most common. Regarding the symmetry of MF, it was symmetrically located in majority (54.9%) of our cases. The higher percentage of symmetry was observed in other populations; for example, 90.4% in Turkish, 77% in North Jordanian, 82.7% in Kurdish, 85.7% in Iranians. Few studies have shown lower percentage of symmetry among Asian Indians.[27],[30] No single study showed 100% of symmetry of MF positioning on both sides, which clearly indicates that MF is not always symmetrical in same individuals.


   Conclusion Top


Based on the present study, we can conclude that the separate type of MF was the most common in both genders. The MF was situated along the longitudinal axis of second premolar (position 4) predominantly. It may be symmetrical or asymmetrical in an individual with no differences among genders.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
   References Top

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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

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