Mental foramen of mandible in South Kerala population - A digital radiographic study

Introduction

Mental foramen is defined as an opening of the mental canal onto the lateral surface of mandible.1 The mental nerve which is a branch of inferior alveolar nerve exits the mandible through the mental foramen. The most common shape of mental foramen found in Indian population is round followed by oval horizontal.2 Personal identification using metric and nonmetric features is important in forensic studies.3 The position of mental foramen can guide in determining the age and sex of an individual.4 Identification of individuals from the features of teeth and jaw has been used from the time of Romans. Forensic dentists and anthropologists use the morphological features of mandible in determination of sex.5 Among different landmarks in human skull, mental foramen is a stable landmark in mandible.6 The position of mental foramen can be located with the help of orthopantomogram.

The aim of the present study was to compare the vertical distance of the lower border of mandible from the superior border and inferior border of mental foramen in both males and females using orthopantomogram.

Materials and Methods

A quantitative observational study of two-year duration was done in Government Dental College, Alappuzha. The sampling technique used was convenient sampling technique. The digital orthopantomogram of patients vising the outpatient department of Dental College for orthodontic corrections were selected for the study. Radiographs meeting the inclusion and exclusion criteria were included in the study.

Results

The mean distance from the upper border of mental foramen to lower border of mandible in males is 13.60mm compared to 12.09mm in females (Figure 1, Figure 2). A statistically significant difference obtained in the mean distance from the upper border of mental foramen to the lower border of mandible between males and females (P<0.001) (Table 1). The mean distance from the lower border of mental foramen to lower border of mandible in males is 11.21mm compared to 10.02mm in females (Figure 1, Figure 2). A statistically significant difference obtained in the mean distance from the lower border of mental foramen to the lower border of mandible between males and females(P<0.005) (Table 2).

Figure 1

(a): Showing the distance from superior border of mental foramen to base of mandiblein males (b): Showing the distance from inferior border of mental foramen tobase of mandible in males

Figure 2

(a): Showing the distance from superior border of mental foramen to base of mandiblein females (d): Showing the distance from inferior border of mental foramen tobase of mandible in females

Discussion

Sexual dimorphism in humans is used for personal identification in forensic odontology. Men requires more calories than women to maintain a healthy body weight.7 The greater masticatory muscle size and greater maxillary molar bite force may be responsible for the facial sexual dimorphism.8 Identification of skeletal remains is important in anthropology and forensic investigations. Previous studies show that there are significant differences in relation to race and sex in mandible. These differences are determined by different growth factors and environmental factors.9 As there is an increase in population intermixing, population specific standards are important in the present situation.10

Mandible is one of the most durable and hardest bone of facial skeleton. Mandible is subjected to great stress due to the process of mastication.11 Mandible can be used with increased sensitivity and specificity for identifying both males and females.12 Sexual dimorphism of mandible is due to the difference in growth pattern and maturation rate of bone which occurs early in females compared to males. Mandible in males found to be more robust than in females. Among the skull bones, mandible is the last bone to stop growth.13 The size of mental foramen has a tendency to increase with age in females and has tendency to decrease with age in males and it is due to the influence of sex hormones.14

In the present study, the distance of the superior and inferior border of mental foramen from the base of mandible found to be greater in males compared to females. Rashid and Ali in 2011 studied the position of mental foramen in Iraqi population and obtained similar results.15 Chandra A et al in 2014 found similar findings in their study in North Indian population.6 Sheikhi M and Kheir M K in 2016 studied the position of mental foramen using CBCT in Irani population and found the distance of mental foramen from lower border of mandible to be greater in males than females.16 Malik M et al in 2016 found similar results in Haryana population.17 Elgazzar et al in 2016 in Egyptian population found sexual dimorphism in the position of mental foramen.18 Rodriguez Cardenar YA in 2018 studied the distance of lower border of mental foramen to base of mandible in Peruvian subjects and found the measurements were found to be greater in males.19 Rani A et al in 2019 studied the position of mental foramen in West Bengal population and found results similar to our study.20 Renjith G et al in 2019 studied the position of mental foramen in Chinese population and confirmed the presence of sexual dimorphism with the help of discriminant function analysis.21 Atallah H N et al in 2019 studied the position of mental foramen using Computed Tomographic analysis in Iraqi population and found similar results.22 Subhash T S et al in 2019 got similar results in Karnataka population.

TM Wang et al in 100 Chinese cadavers measured the distance of lower border of mandible from lower border of mental foramen and found to be 14.7mm.23 Mandible exhibits high degree of sexual dimorphism.11 The mental foramen lies below the depressor labii inferioris muscle. The greater distance of the mental foramen from lower border of mandible may be due to the decrease in size of mental foramen due to increase in muscle pull in males compared to females.

Conclusion

The results from this study focus on the sexual dimorphism of mental foramen in an Indian sub-population. The study can be carried with more sample size to know the specificity of the results. Location of mental foramen can be used as an adjunct tool in forensic identification of sex.

Source of Funding

This research did not receive any funding.

Conflict of Interest

Nil.

Acknowledgement

Authors acknowledge technical help done by radiographers Smt. Jaseem Sajil and Mr. Aravindakshan.