Mental foramen morphometrics on cone-beam computed tomography determines sexual dimorphism

Satarupa Chanda; Reema Manoj; Vasavi Santosh; Arvind Shetty; Mandavi Waghmare; Hemant Bhutani

doi:10.4103/aihb.aihb_168_21

ORIGINAL ARTICLE

Year : 2023 | Volume : 13 | Issue : 1 | Page : 36-41

Mental foramen morphometrics on cone-beam computed tomography determines sexual dimorphism

Satarupa Chanda¹, Reema Manoj¹, Vasavi Santosh¹, Arvind Shetty², Mandavi Waghmare¹, Hemant Bhutani¹
¹ Department of Oral Medicine and Radiology, DY Patil University School of Dentistry, Navi Mumbai, Maharashtra, India
² Department of Periodontics and Oral Implantology, DY Patil University School of Dentistry, Navi Mumbai, Maharashtra, India

Date of Submission	01-Dec-2021
Date of Acceptance	24-May-2022
Date of Web Publication	06-Dec-2022

Correspondence Address:
Dr. Satarupa Chanda
No 169 LIC Township Madhyamgram, 24PGS North, Kolkata - 700 129, West Bengal
India

Source of Support: None, Conflict of Interest: None

Check

DOI: 10.4103/aihb.aihb_168_21

Abstract

Introduction: Identification of humans during a lifetime, as well as acknowledgment even after death, is an inalienable right and forms the core of human dignity. A pivotal step in the identification of human remains is sex determination, as age and stature discernment depends on it. Determination of sex from unknown skeletal remains is extremely challenging, especially when fragmented bony remains are available. Among the various morphological landmarks of the mandible, the mental foramen is considered to be one of the most stable that can be used in sex authentication. Hence, it was used to identify a sexual dimorphism in a mixed Indian population in the present study. Materials and Methods: Two-hundred cone-beam computed tomography (CBCT) scans were selected from the archival database and analysed for the present study using morphometric features of the mental foramen i.e., the measurement of: The distance from the superior border of the mental foramen to the inferior border of the mandible (SLM), The distance from the inferior border of the mental foramen to the inferior border of the mandible (ILM) and the distance from the superior border of the mental foramen to the inferior border of the mental foramen (VD). Results: Females showed a caudal positioning of mental foramen toward the base of the mandible as compared to males. A statistically significant difference was noted in the dimensions of SLM, ILM and VD, with all the three distances being larger in males when compared to females. Logistic regression analysis showed an overall significance of P < 0.0001 and a prediction score of 89%. Conclusion: Mental foramen morphometrics on CBCT enables sex determination in the Indian population with a predictive score of 89%.

Keywords: Cone-beam computed tomography, gender determination, mental foramen, sexual dimorphism

How to cite this article:
Chanda S, Manoj R, Santosh V, Shetty A, Waghmare M, Bhutani H. Mental foramen morphometrics on cone-beam computed tomography determines sexual dimorphism. Adv Hum Biol 2023;13:36-41

How to cite this URL:
Chanda S, Manoj R, Santosh V, Shetty A, Waghmare M, Bhutani H. Mental foramen morphometrics on cone-beam computed tomography determines sexual dimorphism. Adv Hum Biol [serial online] 2023 [cited 2023 Mar 27];13:36-41. Available from: https://www.aihbonline.com/text.asp?2023/13/1/36/362700

Introduction

Sex, age and race are the determining characteristics for every human individual, among which discerning sex is believed to be the essential aspect of human identification.^[1]

The reliability of sex determination depends on the completeness of the human remains available and the degree of sexual dimorphism in the population. When the entire adult skeleton is available, the sex can be determined with 100% accuracy.^[2] The fragmented bone-like skull can predict sex with 92% accuracy. However, when the entire skull is unavailable, the mandible can play a vital role. The mandible is the strongest bone and can withstand the taphonomic process much better than the other skeletal structures. Among various physiognomic features of the mandible that can be used in forensics, the mental foramen is considered to be one of the most stable landmarks.^[3]

It is a funnel-like opening on the lateral surface of the mandible at the terminus of the mental canal that lies near the apices of the premolars and transmits the mental nerves and vessels.^[4] The mental canal opens superiorly and posteriorly in the mandible, and due to this reason, it is usually visible only 50% of the time in a two-dimensional view.^[5] Hence, two-dimensional images have their fair share of drawbacks and inaccuracies. Due to the upswing of technology, cone-beam computed tomography (CBCT) proves to provide near accurate location and measurements of the anatomical landmarks.

The literature reveals that studies^[6] on the estimation of sex by mental foramen morphometrics using CBCT are exiguous and warrant further research.

Hence, we conducted this study in the mixed Indian adult population to differentiate sex by morphometric analysis of mental foramen.

Materials and Methodology

Sample size

Three hundred CBCT scans were screened in the 1-year interval between 2018 and 2019 from the archival database of Government Dental College and Hospital, Mumbai, after receiving approval (IREB/2020/OMDR/04) from the Institutional Research and Ethical Board of D. Y. Patil University School of Dentistry, Navi Mumbai.

After meeting the given inclusion and exclusion criteria, whole mandible CBCT images of 200 patients were retrieved and analysed for morphometric measurement of the mental foramen. Only high-quality images showing the entire mandible with known patient's age, sex and origin and identifiable required features were selected. Subjects between 20 and 60 years of age were considered. Scans with completely edentulous mandible or with evidence of any developmental anomalies/large intraosseous lesions/fractures/reconstruction surgery involving the mandible were excluded. Scans with the presence of pathology in the apical area of premolars and mental foramen or with the presence of accessory mental foramen were also excluded.

Image evaluation

CBCT images were acquired and selected using the Planmeca Pro Max 3D apparatus with standard protocol: A peak kilovoltage-90kvp, tube current-10 mA and voxel size ranging between 0.2 and 0.6 mm depending on the variable field of view.

The Planmeca Romexis Viewer software was used for the reconstruction and measurement of the scans, which were done in the paraxial view. Adjustments were made using the adjustment tools for improving visibility. All scans were evaluated by a single investigator (oral radiologist) to avoid inter-observer discrepancies and were statistically analysed.

CBCT projections were analysed in different cross-sectional planes to identify the mental foramen. In order to assess its vertical position and vertical diameter (VD), three coronal sections were obtained on each side of the mandible with the least slice thickness of 0.6 mm between them, and the best image section was then utilised for analysis.

Assessment of vertical position of the mental foramen to the base of the mandible

SLM-The distance from the superior border of the mental foramen to the inferior border of the mandible
ILM-The distance from the inferior border of the mental foramen to the inferior border of the mandible.

Assessment of VD of mental foramen

VD-The distance from the superior border of the mental foramen to the inferior border of the mental foramen.

Three tangents were drawn from the superior and inferior border of mental foramen and the base of the mandible. Following this, perpendiculars were drawn from the tangents to the lower border of the mandible respectively on both the sides of the mandible using the ruler software to assess SLM, ILM and VD [Figure 1].

Figure 1: Tangents marked (black lines) to show the superior margin and inferior mergin of mental foramen and base of mandable. SLM (longer green line), ILM (shorter green line) and VD (red line) are shown respectively in the bast cross-sectional view showing the max imumdistance.

Click here to view

Data analysis

All data were entered into a Microsoft Office Excel (version 365, Microsoft Office, Mumbai, India) in a spreadsheet and checked for errors and discrepancies. Data analysis was done using windows based 'MedCalc Statistical Software' version 19.0.6 (MedCalc Software bvba, Ostend, Belgium; http://www.medcalc.rorg; 2020). Measurement data are expressed as means with standard deviation and standard error of the mean. Categorical data are expressed as numbers and percentages.

Statistical analysis

The data obtained were analysed statistically. An independent t-test was used to compare the distance between the reference points and between the sexes. Wilcoxen's correlation coefficient test was used to assess the strength of the correlation between the right and left sides. Comparison between age groups was analysed by Mann–Whitney U-test. Confidence intervals at 95% of each parameter were calculated. Further logistic regression analysis was made, and the predictive percentage was calculated.

Results

Among 200 CBCT images, 101 images were of males, and 99 were of females between 20 and 60 years of age. The mean age of the patients was 37.04 ± 14.36. As the position and location of mental foramen are relatively stable in adulthood, when compared to pediatrics and adolescents, adults of 20–60 years were considered for the study.

Mental foramen was present on both sides of all the images, and SLM ILM and VD were compared among males and females [Table 1]. On comparing the right side with the left side among all the parameters, no statistically significant difference was found, suggesting any of the sides could be used for sex determination [Table 2]. When age groups were divided into two categories i.e 20-39yrs and 40-60yrs, there was no significant difference in the male and female numbers suggestive of equal gender distribution [Table 3].

Table 1: Comparison of SLM, ILM, VD on each side between males and females

Click here to view

Table 2: Comparison of SLM, ILM, VD on right and left side

Click here to view

Table 3: Age versus gender distribution

Click here to view

Comparison of the measurements in different age groups

Males and females were divided into two age groups – 20–39 years and 40–60 years and all the parameters, namely SLM, ILM and VD, were compared between males and females, respectively. All the parameters showed a statistically significant difference between sex in both the age groups [Table 4] and [Table 5].

Table 4: Comparison of SLM, ILM, VD on each side between males and females in the age Group of 20-39 years

Click here to view

Table 5: Comparison of SLM, ILM, VD on each side between males and females in the age group of 40-60 years

Click here to view

On comparing SLM, ILM and VD across the two age groups, it showed no statistically significant difference, suggestive of no difference in the parameters with respect to age [Graph 1].

Logistic regression analysis

Using enter LR method showed an overall significance of P < 0.0001 and a prediction score of 89.00%. Male = 1; Female = 0 [Table 6].

Table 6: The prediction accuracy model

Click here to view

Using individual parameters, VD on the left side showed the highest predictive power of 79.50%.

Discussion

Various methods have been considered by forensic experts for analysing sex from a skeletal specimen which includes molecular, morphological and morphometrical techniques.^[1] Molecular analysis of DNA for sex determination can create challenges for forensic experts as a result of sample degradation and contamination.^[7] Morphological features, on the other hand, are subjective and have higher chances of inaccuracy, while morphometric methods are considered expeditious, simple, reliable and cost-effective.^[8] Hence, these parameters were considered in our study.

The morphometric parameters of the mental foramen can be established using a human cadaver mandible as well as by means of various radiographic techniques.^[9] Panoramic radiographs were used to a great extent due to their large availability but had their share of discrepancies. The radiographic mental foramina on an orthopantomogram represent a section of the mental canal and not the foramen itself.^[6] Other than this, the technique has certain limitations such as magnification, geometric distortion, artifacts and sensitivity to positioning errors due to narrow focal trough, all of which may contribute to the inaccurate reproducibility of dimensions and locations of the mental foramen.^[8] But with advancements and the advent of 3D imaging cone-beam computed tomography, which provides images in 1:1 ratio, these pitfalls of panoramic radiographs could be avoided providing better accuracy and hence was used in our study for sex identification.

In the present study, adults in the age group of 20–60 years were considered as the position and diameter of mental foramen are relatively stable during this stage when compared to the pediatric and adolescent age groups.^{[10],[11],[12]}

In our study, the vertical positioning of mental foramen was determined by measuring the SLM and ILM. These parameters showed significant sexual dimorphism, with males having an average greater distance than females. This was in accordance with the study conducted by Subash et al. in 2018 in the south Indian population.^[6] Similar results were obtained in other non-Indian population studies such as in the Polish (2019),^[13] Egyptian (2020),^[9] and Peruvian population (2020).^[14] However, in contrast, a study conducted in the Iranian population by Shams et al. in 2019 showed no sexual dimorphism with respect to vertical positioning of the mental foramen.^[15] This could be due to the difference in the racial population and sample size.

VD obtained in the present study also showed sexual dimorphism, with males having an average larger diameter than females. This corresponded with other CBCT studies conducted in non-Indian populations by Zmyslowska-Polakowska et al., Gungor et al., Zhang and Zheng, and Kalender et al.^{[13],[16],[17],[18]} Various panoramic studies conducted in the Indian population also showed similar results.^{[3],[4],[19],[20],[21]}

Our study suggested any side of the mandible could be used for sex identification with no significant difference in the parameters between the right and left sides of the mandible. However, Subash et al. concluded statistically significant differences in SLM distance between the right and left sides with no significant difference between the right and left ILM distance.^[6] This could be due to the difference in sample selection. Von Arx et al.,^[10] and Kalender et al.,^[18] however, found no changes in the right and left side of the vertical position of mental foramen with respect to the lower border of the mandible. Our study also suggested no changes in the vertical position of the mental foramen and VD with the advancement of age. This did not corroborate with the study conducted in the Egyptian population, where the mental foramen-lower border of mandible position of some Egyptians was not constant and changed with advancements of age.^[22] This could be due to ethnic differences. However, no similar study was done in the Indian population using CBCT imaging, suggesting the requirement of more such studies to establish the relationship. According to a study in the Jordan population in 2018,^[23] there is a tendency for an increase in MF size with age in females as opposed to a tendency for size reduction with age in males, suggesting a role of sex hormones in influencing MF size.

Confidence interval analysis in the present study showed 95% suggesting that if SLM is more than 16.85 mm, ILM more than 13.32 mm and VD more than 3.46 mm, the sex will be made in 95% of the cases. Similarly, if SLM is < 14.27 mm, ILM < 11.74 mm and VD < 2.37 mm, the sex will be female in 95% of the cases. The results were similar to the study conducted on a south Indian population by Subash et al. in 2018.^[6]

The accuracy of sex prediction in the present study, based on logistic regression analysis, was 89% using cumulative measurements of all six parameters. Using individual parameters, VD on the left side showed the highest predictive power of 79.50%.

Limitations and future prospects

As observed in this study, identification of the superior border of the mental foramen, which is generally in continuation with the body of the mandible, was challenging in certain cases, which could also be one of the attributing factors in the variations of the result.

Future studies on a larger scale on the Indian population must be done using CBCT for the identification of sex, keeping different age groups into consideration.

Transgenders and transsexuals form an integral part of our society that disrupts the binary concept of gender. The alteration in their sexual hormones may have an indirect impact on the skeletal growth of the individual, which in turn may lead to an inaccurate gender identification from unknown skeletal remains. Hence, researchers should continue to explore the full biological spectrum of the human body as well as contribute to an important discussion about the remains that do not fit the standard binary model.

Conclusion

Based on the results of the present study, it is possible to conclude that the population exhibited sexual dimorphism where females had a more caudal or lower position of the mental foramen to the base of the mandible and a smaller diameter when compared to males. We could also conclude that SLM, ILM and VD remain considerably constant in the different age groups of adults.

The cumulative measurements of all these parameters provided a powerful predictive score of 89% and hence could be used as a stable morphometric assessment tool in future studies for assessing sex.

Acknowledgment

(1) Government Dental College and Hospital, Mumbai, for acquiring of CBCT Scans. (2) Dr. Deepak Langade - Statistical Analysis.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

1.	Capitaneanu C, Willems G, Thevissen P. A systematic review of odontological sex estimation methods. J Forensic Odontostomatol 2017;35:1-19.
2.	Alias A, Ibrahim A, Abu Bakar SN, Swarhib Shafie M, Das S, Abdullah N, et al. Anthropometric analysis of mandible: An important step for sex determination. Clin Ter 2018;169:e217-23.
3.	Sahni P, Patel RJ, Shylaja, H. M J, Patel A. Gender determination by pantomographic (OPG) analysis of mental foramen in north Gujarat population- A retrospective study. Med. Res. Chron [Internet]. 2015; 2:701-6.
4.	Chandra A, Singh A, Badni M, Jaiswal R, Agnihotri A. Determination of sex by radiographic analysis of mental foramen in North Indian population. J Forensic Dent Sci 2013;5:52-5. [PUBMED] [Full text]
5.	Rani A, Kanjani V, Kanjani D, Annigeri RG. Morphometric assessment of mental foramen for gender prediction using panoramic radiographs in the West Bengal population – A retrospective digital study. J Adv Clin Res Insights 2019;6:63-6.
6.	Subash TS, Balaraj BM, Hema C. Determination of sex by cone-beam computed tomography analysis of mental foramen in South Indian population. Int J Forensic Odontol 2019;4:21-6. [Full text]
7.	Alonso A, Andelinović S, Martín P, Sutlović D, Erceg I, Huffine E, et al. DNA typing from skeletal remains: Evaluation of multiplex and megaplex STR systems on DNA isolated from bone and teeth samples. Croat Med J 2001;42:260-6.
8.	Heena M, Bhuvaneshwari S, Singh Mohit P, Prashant N, Kanishk M, Tulika S. Gender determination using mandibularramus and gonial angle on OPG. J Indian Acad Oral Med Radiol 2020;32:154-8.
9.	Mousa A, El Dessouky S, El Beshlawy D. Sex determination by radiographic localization of the inferior alveolar canal using cone-beam computed tomography in an Egyptian population. Imaging Sci Dent 2020;50:117-24.
10.	von Arx T, Friedli M, Sendi P, Lozanoff S, Bornstein MM. Location and dimensions of the mental foramen: A radiographic analysis by using cone-beam computed tomography. J Endod 2013;39:1522-8.
11.	Carruth P, He J, Benson BW, Schneiderman ED. Analysis of the size and position of the mental foramen using the CS 9000 cone-beam computed tomographic unit. J Endod 2015;41:1032-6.
12.	Muinelo-Lorenzo J, Fernández-Alonso A, Smyth-Chamosa E, Suárez-Quintanilla JA, Varela-Mallou J, Suárez-Cunqueiro MM. Predictive factors of the dimensions and location of mental foramen using cone beam computed tomography. PLoS One 2017;12:e0179704.
13.	Zmyslowska-Polakowska E, Radwanski M, Ledzion S, Leski M, Zmyslowska A, Lukomska-Szymanska M. Evaluation of size and location of a mental foramen in the Polish population using cone-beam computed tomography. Hindawi Biomed Res Int 2019;2019:8.
14.	Rodríguez-Cárdenas YA, Casas-Campana M, Arriola-Guillén LE, Aliaga-Del Castillo A, Ruiz-Mora GA, Guerrero ME. Sexual dimorphism of mental foramen position in peruvian subjects: A cone-beam-computed tomography study. Indian J Dent Res 2020;31:103-8.
15.	Shams N, Razavi M, Mehrabi A, Salehin S, Sarikhani P. Determining gender and age by mandibular anatomy landmarks in computed tomography with cone-beam (CBCT). J Mol Biol Res 2019;9:8.
16.	Gungor E, Aglarci OS, Unal M, Dogan MS, Guven S. Evaluation of mental foramen location in the 10-70 years age range using cone-beam computed tomography. Niger J Clin Pract 2017;20:88-92. [PUBMED] [Full text]
17.	Zhang L, Zheng Q. Anatomic relationship between mental foramen and peripheral structures observed by cone-beam computed tomography. Anat Physiol 2015;5:182.
18.	Kalender A, Orhan K, Aksoy U. Evaluation of the mental foramen and accessory mental foramen in Turkish patients using cone-beam computed tomography images reconstructed from a volumetric rendering program. Clin Anat 2012;25:584-92.
19.	Thakur M, Reddy KV, Sivaranjani Y, Khaja S. Gender determination by mental foramen and height of the body of the mandible in dentulous a radiographic study. J Indian Acad Forensic Med 2014;36:13-8.
20.	Ghouse N, Nagaraj T, James L, Swamy NN, Jagdish C, Bhavana TV. Digital analysis of linear measurements related to the mental and mandibular foramina in sex determination. J. Med. Radiol.Pathol. Surg. 2016;2:5-9.
21.	Suragimath G, Ashwinirani SR, Christopher V, Bijjargi S, Pawar R, Nayak A. Gender determination by radiographic analysis of mental foramen in the Maharashtra population of India. J Forensic Dent Sci 2016;8:176. [PUBMED] [Full text]
22.	Shaaban A, El-Shall O. Study of Age and Gender Related Variations in Position of Mental Foramen of Some Egyptians Using Digital Panoramic Radiography. Ain Shams Journal of Forensic Medicine and Clinical Toxicology, 2017;29:36-47.
23.	Alsoleihat F, Al-Omari FA, Al-Sayyed AR, Al-Asmar AA, Khraisat AS. The mental foramen: A cone beam CT study of the horizontal location, size and sexual dimorphism amongst living Jordanians. Homo : internationale Zeitschrift fur die vergleichende Forschung am Menschen 2018;69: 335-9.