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 Table of Contents  
FORENSIC ODONTOLOGY: ORIGINAL ARTICLE
Year : 2020  |  Volume : 32  |  Issue : 2  |  Page : 154-158

Gender determination using mandibular ramus and gonial angle on OPG


1 Department of Oral Medicine and Radiology, Darshan Dental College, Udaipur, Rajasthan, India
2 Department of Oral Medicine and Radiology, Kiit University, Bhuvaneshwar, Odisha, India
3 Department of Oral Medicine and Radiology, Pacific Dental College, Udaipur, Rajasthan, India
4 Department of Ent and Head Neck Oncosurgeon, Gbh American Hospital, Udaipur, Rajasthan, India

Date of Submission20-Sep-2019
Date of Decision08-May-2020
Date of Acceptance09-May-2020
Date of Web Publication27-Jun-2020

Correspondence Address:
Dr. Kanishk Mehta
Department of ENT and HNS, GBH American Hopsital, 101, Kothi Bagh, Bhatt Ji Ki Bari, Udaipur - 313 004, Rajasthan
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jiaomr.jiaomr_169_19

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   Abstract 


Background: The forensic osteologist is usually asked to provide information that may confirm, or assist in determining, the identity of an individual from their skeletal remain. Mandibular ramus can differentiate between the two genders as the stages of mandibular development, growth rates, and duration are distinctly different in both sexes. Aim: To measure and evaluate the various dimensions of the mandibular ramus and the angle of the mandible as observed on orthopantomogram (OPG) and compare it with both sexes. Setting and Design: It is a retrospective study where OPG of 900 mandibles were studied on each side and analyzed to evaluate gender variations. Materials and Methods: KODAK 8000C Digital Panoramic and Cephalometric System and Masterview 4.5.4 software was used for data tabulation. Statistical Analysis: Descriptive analysis was used to analyze the results. Result and Conclusion: Mandibular ramus breadth and gonial angle have been found to be the most reliable parameters in gender determination

Keywords: Gender determination, gonial angle, mandibular ramus


How to cite this article:
Mehta H, Bhuvaneshwari S, Singh MP, Nahar P, Mehta K, Sharma T. Gender determination using mandibular ramus and gonial angle on OPG. J Indian Acad Oral Med Radiol 2020;32:154-8

How to cite this URL:
Mehta H, Bhuvaneshwari S, Singh MP, Nahar P, Mehta K, Sharma T. Gender determination using mandibular ramus and gonial angle on OPG. J Indian Acad Oral Med Radiol [serial online] 2020 [cited 2020 Jul 11];32:154-8. Available from: http://www.jiaomr.in/text.asp?2020/32/2/154/288125




   Introduction Top


Identification of ancestry is important in both forensic contexts and bioarchaeological research.[1] After identification of human species, accurate gender determination from skeletal remains is the first step toward making individual identification. In all human populations, adult male and female skeletons reflect different shape and size characteristics.[2] This forms the basis of forensic anthropology. Three basic criteria should guide the choice of skeletal elements that may be useful indicators of gender: Their morphology should clearly reflect anatomic and/or physiologic sex differences, they should be able to withstand the rigors of skeletonization and fossilization, and ideally the trait should be recognizable through time.

The reliability of gender determination depends upon the completeness of the remains and the degree of sexual dimorphism inherent in the population. When the entire adult skeleton is available for analysis, gender can be determined with up to 100% accuracy, but in cases of mass disasters where usually fragmented bones are found, sex determination depends largely on the available parts of the skeleton. The skull, followed by the pelvis, is the most commonly employed component of the skeleton for the purpose of gender determination. In cases where the intact skull is not found, mandible may play a vital role in sex determination as it is the most dimorphic bone of the skull. The mandible is the largest and strongest bone of the face. The presence of a dense layer of compact bone makes it very durable and hence remains well preserved than many other bones. Dimorphism in the mandible is reflected in its shape and size.[3]

Although some researchers have devised discriminant functions that make use of parameters pertaining to individual parts of the mandible (Giles, 1964; Saini et al., 2011), but the results obtained are population specific. Therefore, there is a need for development of population specific discriminant function. Panoramic radiographs (OPG) are a useful tool for the measurement of mandible.[4] Several studies have been conducted on dry adult mandibles for gender determination, but a literature search did not reveal any study with regard to measurements on ramus of the mandible and gonial angle using a OPG. This study was conducted with the aim to measure and evaluate the various dimensions of mandibular ramus and the angle of mandible as observed on OPG and compare with both sexes.


   Materials and Methods Top


The present study is a retrospective quantitative analytical study. Data was obtained from the records of 1800 patients who visited the department of oral medicine and radiology, Pacific Dental College, Udaipur and underwent a radiolographic investigation of panoramic radiograph (OPG) from July 2015 to June 2016 using KODAK 8000C Digital Panoramic and Cephalometric System and Masterview 4.5.4 software. Due to unavailability of cone-beam computed tomography (CBCT) in the institute at the time of commencement of the study, OPG was selected for radiological analysis. Single observer readings were computed to avoid any interobserver variations. The mean of right and left side of ramus was calculated for parameter on each OPG, and finally the values obtained for males and females were compared. Denatate subjects between the age group of 20 years to 50 years of age were included in the study while OPGs taken for trauma and fractures involving the mandibular ramus, developmental disturbances of the mandible, magnification errors (vertical and horizontal), and the distortion and presence of supernumerary teeth were excluded. The following parameters were measured on both sides and mean values were taken [Image 1] and [Image 2]:



  • Maximum Ramus breadth: The distance between the most anterior point on the mandibular ramus and a line connecting the most posterior point on the condyle.
  • Minimum Ramus breadth: The distance between the most posterior point on the anterior border of the ramus to the most anterior point on the posterior border of the ramus.
  • Condylar height (maximum ramus height): Height of the ramus of the mandible from the most superior point on the mandibular condyle to the tubercle or most protruding portion of the inferior border of the ramus.
  • Projective height of the ramus: Projective height of ramus between the highest point of the mandibular condyle and lower margin of the bone.
  • Coronoid height: Projective distance between coronoid and lower wall of the bone.
  • Angle of Mandible: Angle formed between tangents to inferior border of body and posterior border of ramus of mandible


The data obtained were tabulated and subjected to statistical analysis using paired sample t-test to compare the difference between males and females.


   Results and Observations Top


The total number of OPGs included in this study was 1800. There were 900 males and 900 females. Male: female ratio is 1:1. All subjects were divided into 3 categories of 10 years each i.e., 20–30 years of age, 30–40 years of age, and 40–50 years of age [Table 1]. The mean age of males was 33 years while that of females was 30 years.
Table 1: Age vs sex distribution

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Descriptive statistics of all the mandibular ramus parameters on OPG is shown in [Table 2]. All the six measurements were found to be statistically significant (P value < 0.001), and hence each variable was a significant predictor in classifying the gender. All the parameters have higher male measurements than females except gonial angle, which was significantly higher in females than in males. When the discriminant value was obtained and accuracy of these parameters was calculated, it was found that ramus breadth (minimum and maximum) along with mandibular angle had highest accuracy in sexing the mandible on OPG with rates of 77.3%, 76.7%, and 76%, respectively while projective height showed least reliability to predict the gender accurately among the parameters under study with a rate of 72.4% [Table 3]. The overall accuracy rate was around 75%. However, the accuracy increases to more than 85% when two or more predictors were cumulatively calculated for gender determination of the mandible.
Table 2: Table showing summary of descriptive statistical analysis among males and females

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Table 3: Table showing percentage (%) accuracy of all parameters towards gender determination

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In the present study, there were 335 males and 374 females of 20–30 years of age group; 236 males and 250 females of 31–40 years of age group; and 330 males and 275 females of 41–50 years of age group.


   Discussion Top


The identification of sex from human remains is of fundamental importance in forensic medicine and anthropology, especially in criminal investigations as well as in the identification of missing persons and in attempts at reconstructing the lives of ancient populations. Identification of sex based on morphological marks is subjective and likely to be inaccurate, but methods based on measurements and morphometry are accurate and can be used in the determination of gender from the skull.[5] Mandibles were used for the analysis for two simple reasons: firstly, there appears to be a paucity of standards utilizing this element, and secondly this bone is often recovered largely intact. The population specificity of the discriminant function method of sex determination using the mandible has been put forward by many authors.

Sexual dimorphism exhibited by the skull is mainly dependent upon changes that occur in the male at puberty that reflect increased muscle attachment, whereas the female skull tends to retain pedomorphic features.[6] The male mandible generally has a greater body height, more prominent chin and robust lower border, and more prominent muscle markings than in the female.[7] The gonial angle formed between the body and ramus is less obtuse than in the female. Calcagno (1981) and Maat et al. (1997) found that accuracy of gender determination was seriously affected by the size of the mandible. More recently Loth and Henneberg (1996, 1998) described a flexure in the posterior border of the ramus that was present in male but absent in female mandibles, which they claimed determined the gender with an accuracy of 94%. There is also good evidence showing that dietary factors can influence the expression of sexual dimorphism. It has been proposed that males are more susceptible to fluctuations in nutritional quality, hence growth is reduced to a greater degree than in females, thus resulting in a more equal body size and reduced dimorphism. Moss demonstrated that hypertrophy of the “masseter”muscle is associated with expansion and flaring of the angular process. Cultural activities, such as daily chewing of a tough material (tobacco, betel nut, resin etc) has been shown to increase facial height, with other flow-on effects to the mandible, including, but not limited to, increased prognathism and a reduction in gonial angle.

Orthopantomogram has been advocated routinely and widely used by the clinicians as an appropriate screening tool for the diagnosis of oral diseases.[8] It is considered as an adjuvant radiographic method to differentiate gender as it provides ground for the measurements of various landmarks from skeletal remains.[9] The principal advantages of panoramic images are their broad coverage, low patient radiation dose, and the short time required for image acquisition. Other advantages are that interference of superimposed images is not encountered. Also the contrast and brightness enhancement and enlargement of images provide an accurate and reproducible method of measuring the chosen points.[10] The limitations of this technique are magnification and geometric distortion, the vertical dimension in contrast to the horizontal dimension is little altered, and this technique is quite sensitive to positioning errors because of relatively narrow image layer.[11] However, in our study, this limitation did not affect our results since all images were uniformly magnified. Kambylafkas et al. concluded that the use of the panoramic radiograph for evaluation of total ramus height is reliable and an asymmetry of more than 6% is an indication of a true asymmetry.

This study includes total 1800 mandibles, which is one of the largest study samples available in literature. Each of the six variables measured on mandibular ramus using orthopantomograph showed statistically significant gender differences, indicating that ramus expresses strong gender dimorphism. The mandibular ramus demonstrated greatest univariate dimorphism in terms of maximum and minimum ramus breadth, condylar height, followed by the projective height of ramus. This is consistent with other studies in literature. Overall prediction accuracy rate using maximum ramus breadth was 77.3% while that of minimum ramus breadth was 76%. This is comaprable to the findings of Indira et al. who concluded an accuracy rate of 76% and Franklin et al. who got an accuracy rate of 77%.[12],[13]

Earliest studies on mandible by Morant et al. (1936), Martin (1936), and Hrdlicka (1940) (cited in Humphrey et al.) have established the usefulness of mandible for the determination of gender. They found that the gender differences were highest in height of the ramus, thus emphasizing that the differences are more pronounced in mandibular ramus than in body.[14] Humphrey et al. emphasized that almost any site of mandibular bone deposition, or resorption, or remodeling for that matter, seems to have a potential for becoming sexually dimorphic. Hence, mandibular condyle and ramus in particular are generally the most dimorphic as they are the sites associated with the greatest morphological changes in size and remodeling during growth. Minimum ramus breadth measurement was found to be the best parameter in the present study, which is consistent with other osteometric studies by Giles (1964)[15] and Vodanovic (2006).[16] This is related to the differences in musculoskeletal development and to the differences related to a different growth trajectory in males and females. However, Neeru (2018) concluded that condylar ramus height has highest dimorphism, whereas ramus breadth had minimum.[17]

Mandibular angle values in males and females range from 123.4° to 132.8° with a mean value of 128.1°. Kumar (2013) had similar findings with a mean of 122.55°.[18] The eversion of angle is characteristic of male and inversion is that of female.[19] It was concluded that round chin mandible with inversion or eversion cannot be a female one and 76.7% percent of accuracy in gender determination is possible with mandibular angle.[20] In the present study, those that are considered as females presented with higher mandibular angle and males with lower mandibular angle. These findings are in agreement with the findings of literatures.

Haun (2000) questioned the predictive accuracy of mandibular ramus as a single indicator of sexual dimorphism and suggested that caution be used when applying this technique in the absence of other morphological and osteometric indicators, especially in the case of fragmentary forensic or rare fossil remains.[20] Giles measured mandibles of known sex using anthropometric measurements and reported mandibular ramus height, maximum ramus breadth, and minimum ramus breadth as highly significant, with an accuracy of 85% in American whites and Negroes. Steyn and Iscan (1998) achieved an accuracy of 81.5% with five mandibular parameters (i.e. bigonial breadth, total mandibular length, bicondylar breadth, minimum ramus breadth, and gonion–gnathion) in South African whites, which is comparable with the present study results.[21],[22] The overall accuracy rates increases to 80.28% while the individual accuracy rates range from 72%–77%. Saini et al. and Neeru et al. conducted a study on dry adult mandibles of the northern part of India and found that ramus expresses strong sexual dimorphism in this population.[23],[24] The overall prediction rate using five variables was 80.2%. There is no study available in literature that combines the ramus measurements with mandibular angle together, which this study elaborates. It was found that when mandibular angle was used along with ramus breadth, the overall accuracy rates increased to 81.1%, which was higher than the two used individually. Thus we can conclude that use of multiple factors when used together were more accurate than any single factor when used alone for gender determination using panoramic radiographs. This is also concluded by Leena James et al. in their elaborate study.[10]

Thus, it has been established that socio-environmental factors (e.g., malnutrition, climate, pathologies, occupation etc.) influences the development and the appearance of bones.[11] Numerous studies have demonstrated that skeletal characteristics differ in each population and have emphasized the need for population-specific osteometric standards for gender determination.[17],[25] Obviously, the highest probability of correct diagnosis of gender comes from a complete examination of all bones known to belong to a given individual-no single skeletal indicator should be relied upon exclusively if other proven dimorphic areas are available.


   Conclusion and Summary Top


In conclusion, the present study has suggested that the accuracy of gender determination using mandibular measurements of the Indian population can be improved by deriving a discriminant function, which utilizes a combination of the six respective dimensions. Our study showed that minimum ramus breadth and maximum ramus breadth are most accurate in predicting gender on OPG while projective height was least reliable. Also, the combinations of multiple measurements used in the study are highly reliable discriminators. Orthopantomogram is a reliable and accurate tool to record the various measurements in order to determine the gender of the given mandible.

Ethical considerations

Requisite ethical clearance was obtained from the Ethical Committee to carry out the study (Ref no PDCH/16/EC -41).

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Tables

  [Table 1], [Table 2], [Table 3]



 

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