|Year : 2014 | Volume
| Issue : 1 | Page : 16-20
Sex determination by mandibular canine index and molar odontometrics: A comparative study
Ramandeep S Narang1, Adesh S Manchanda1, Ranjan Malhotra2, Harsimranjit Singh Bhatia2
1 Department of Oral and Maxillofacial Pathology, Sri Guru Ram Das Institute of Dental Sciences and Research, Amritsar, Punjab, India
2 Department of Periodontology and Oral Implantology, National Dental College and Hospital, Derabassi, Punjab, India
|Date of Submission||03-Sep-2012|
|Date of Acceptance||27-Nov-2013|
|Date of Web Publication||7-Apr-2014|
Adesh S Manchanda
Department of Oral and Maxillofacial Pathology and Microbiology, Sri Guru Ram Das Institute of Dental Sciences and Research, Amritsar, Punjab
Source of Support: None, Conflict of Interest: None
Introduction: Establishment of a person's individuality is important, both for legal and humanitarian purposes. The concept of "identity" is a set of physical characteristics, functional or psychic, normal or pathological, that defines an individual. Sex determination is one of the prime factors employed to assist with the identification of an individual.
Aims and Objective: To investigate the accuracy of mandibular canine index and mandibular first molar mesio-distal odontometrics in sex determination/personal identification in the age group of 20-40 years in a North Indian population.
Materials and Methods: The study sample comprised 410 individuals (200 males and 210 females) of an age group ranging from 20 to 40 years, in a North Indian population. Maximum mesiodistal (MD) diameter of mandibular canines, the linear distance between tips of mandibular canines, and MD diameters of the permanent first mandibular molars were measured using digital vernier callipers on study models.
Results: Sex could be predicted accurately in 67.8% (68% males and 67.6% females) population by mandibular canine index. In molar odontometrics considering the accuracy for individual sex; 84% and 79% accuracy was seen for males in MD dimension of left and right molar respectively followed by 57% and 56% accuracy for females in MD dimension of left and right molar.
Conclusion: Sexual dimorphism of teeth is population specific and among the North Indian population, MD dimensions in mandibular canine and first molar can aid sex determination.
Keywords: Forensic, mandibular canine index, molar odontometrics
|How to cite this article:|
Narang RS, Manchanda AS, Malhotra R, Bhatia HS. Sex determination by mandibular canine index and molar odontometrics: A comparative study. Indian J Oral Sci 2014;5:16-20
|How to cite this URL:|
Narang RS, Manchanda AS, Malhotra R, Bhatia HS. Sex determination by mandibular canine index and molar odontometrics: A comparative study. Indian J Oral Sci [serial online] 2014 [cited 2020 Apr 3];5:16-20. Available from: http://www.indjos.com/text.asp?2014/5/1/16/129944
| Introduction|| |
One of the challenges faced by man in earlier days was to establish the identity of an individual. The concept of "identity" is a set of physical characteristics, functional or psychic, normal or pathological that defines an individual. Identification of an individual is a pre-requisite for certification of death and for personal, social and legal reasons. This establishment of identity is accomplished by age, sex, race and communal characters, dactylography, footprint, complexion, features, hair, stature, deformities, tattoo marks, scars, occupational stigmata, anthropometry, trace evidence factors, etc. 
Sex determination is one of the prime factors employed to assist with the identification of an individual. Correct sex identification limits the pool of missing persons to just one half of the population. In forensic contexts, however, it is not uncommon to recover partial remains, with fragmentary skull and pelvic bones. 
Teeth being the central component of the masticatory apparatus of the skull are good sources of material for civil and medico-legal identification. In addition, the degree to which they provide resistance to damage in terms of bacterial decomposition, fire, and fracture, it makes them valuable for forensic investigation and research. ,
Information concerning tooth size aids in age and sex determination of human remains.  Sex determination using dental features is primarily based upon the comparison of tooth dimensions in males and females or upon the comparison of frequencies of non-metric dental traits like Carabelli's trait of upper molars, deflecting wrinkle of the lower first molars, distal accessory ridge of the upper and lower canines or shoveling of the upper central incisors.  This is based on the fact that although the morphology of the tooth structure is similar in males and females, the size of the tooth does not necessarily remain the same, as the tooth size is determined by cultural, environmental, racial, and genetic factors. 
"Sexual dimorphism" refers to those differences in size, stature, and appearance between male and female that can be applied to dental identification because no two mouths are alike. The existence of sexual dimorphism in the size of the permanent teeth is a well-known attribute of primates, particularly so for the canine teeth, in which the magnitude of the sex difference in the mesiodistal (MD) crown diameter may equal 50% or even more. 
The present article was carried out to investigate the accuracy of mandibular canine index (MCI) and mandibular first molar MD odontometrics in sex determination/personal identification in the age group of 20-40 years in a North Indian population.
| Materials and Methods|| |
The study sample comprised 410 individuals (200 males and 210 females) of an age group ranging from 20 to 40 years, in a North Indian population. This particular age group was studied as ante-mortem insults such as regressive alterations (attrition and abrasion) affecting occlusal and approximal tooth surfaces are minimal. The inclusion criteria for the study are as follows:
- Healthy state of gingiva and periodontium
- Caries free teeth
- Normal overjet and overbite (2-3 mm)
- Absence of spacing in the anterior teeth
- Class I molar and canine relationship bilaterally.
Following informed consent, impressions of the mandibular arch were made with irreversible hydrocolloid (alginate) material and cast poured immediately in type II dental stone to minimize dimensional change. On the study model the following measurements were taken for all the subjects using a digital vernier caliper.
Mandibular canine width was measured as the greater MD dimension of mandibular canine on either side of the jaw. The intercanine distance was measured as the linear distance between the cusp tips of right and left mandibular canine. The observed mandibular canine width and intercanine width were subjected to statistical analysis to assess sex difference using the unpaired t0-test. Intraobserver error was assessed using the paired Student t-test on 50 randomly selected casts. The observed mandibular canine index (MCIo) was calculated using the following formula.
For molar odontometrics the MD diameter of the mandibular first molars was measured using digital vernier calipers on study cast.
MD diameter of the crown: This measurement is the greatest MD dimension between the contact points of teeth on either side of jaw.
The measurements were performed by one person and all values were rounded to two decimal places. Intraobserver error was assessed using the paired Student t0-test on 50 randomly selected casts as done for MCI. The measurements were analyzed using Student's t-test. Statistically significant sexual dimorphisms in male and female odontometric features were tested by the unpaired t0-test.
The mean values of M-D dimensions of males and females were subjected to the following formula  to calculate sexual dimorphism:
Percentage of sexual dimorphism = [(Xm/Xf)-1] ×100
Where Xm = mean male tooth dimension; Xf = mean female tooth dimension.
Data obtained from various measurements was further analyzed using stepwise discriminant function statistics using SPSS version.
| Results|| |
The results of MCI are shown in [Table 1] and [Table 2]. It is evident that the various parameters (inter-canine distance, mandibular canine width, MCI) measured for males and females when compared are statistically different. On comparing the right and left mandibular canine width and indices between males and females, a highly statistically significant difference was found. The intra-observer error was assessed at P < 0.05 level and showed no statistically significant differences. The calculated standard MCI for both males and females were found to be 0.249. With these calculations, we could predict sex correctly in 67.8% of the study population.
|Table 2: Percentage of cases correctly predicted using mandibular canine index|
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On observing the MD diameter of right and left mandibular first molars on the study casts it was seen that the mean values of parameters showed statistically significant differences between males and females with P < 0.05 [Table 3]. Sexual dimorphism was found to be 5.9% and 4.4% in MD dimension of right and left mandibular molar [Table 4], respectively.
|Table 3: Comparison of mean values of different parameters in males and females measured on study casts|
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For MD dimension assessed, several stepwise univariate discriminant function statistics were used to develop a formula to determine sex [Table 5]. Coefficients and sectioning points were calculated for each dimension. The group centroids indicated the average discriminant scores for each sex. Sectioning point is the average of male and female group centroids.
|Table 5: Summary of canonical discriminant function coefficient for the MD dimensions|
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Raw coefficients are the discriminant function coefficients used to calculate the discriminant score. To assess the sex, tooth dimensions are multiplied with the respective raw or unstandardized coefficients (b) and added to the constant (a). If the values (y) thus obtained were greater than the sectioning point the individual was considered a male and if less than the sectioning point the individual was considered female.
i.e. y = a + b (x)
where x is dimension of the tooth in centimeters.
Considering the accuracy for individual sex; 84% and 79% accuracy was seen for males in MD dimension of left and right molar respectively followed by 57% and 56% accuracy for females in MD dimension of left and right molar. The accuracy of sex determination was deliberated with an overall accuracy ranging from 67.5% for MD dimension of right molar to 70.5% for MD dimension of left molar [Table 6].
| Discussion|| |
Although the DNA profile gives accurate results yet measurement of linear dimensions such as arthopometric or odontometric parameters can be used for determination of sex in a large population because they are simple, reliable, inexpensive, and easy to measure. The fact that most teeth complete development before skeletal maturation makes the dentition a valuable sex indicator, particularly in young individuals. 
Considering the fact that there are differences in odontometric features in specific populations, even within the same population in the historical and evolutional context, it is necessary to determine specific population values in order to make identification possible on the basis of dental measurements.  The present study established the impact of sex factor on the morphometry of permanent mandibular canines and first molars in a North Indian population.
Canines differ from other teeth with respect to survival and sex dichotomy. The usefulness of canines as an aid in gender determination by odontometric analyses, in forensic dentistry for example, is supported by their high level of survival in the dentition. The mandibular canines are not only exposed to less plaque, calculus, abrasion from brushing, or heavy occlusal loading than other teeth, they are also less severely affected by periodontal disease and so, usually are the last teeth to be extracted with respect to age.  These findings indicate that mandibular canines can be considered as the "key teeth" for personal identification. 
Mandibular canines are found to exhibit the greatest sexual dimorphism among all teeth.  The notable difference between canine in determining sex was noted to be due to the influence of the Y chromosome which was not uniform in all teeth. On the other hand, the X-linked genetic influence on tooth width was rather uniform for all teeth. 
The measurements of linear dimensions which includes the MD width of canine teeth has the advantage of being able to use a large sample of population because it is simple, inexpensive, and easy to perform. Aggarwal  found that males exhibit larger MD width than females. It is consistent with Nair  who conducted a study on South Indian males and females in the age group of 16-28 years and found that the canines in both jaws exhibited a significant sexual difference. In spite of the tooth size variability factors, the studies conducted by Ghose and Baghdady  on Iraqi population, Lysell and Myrberg  on Swedish population and by Bishara  on populations of Egypt, Mexico, and Iowa showed consistent findings that the MD width of the mandibular canines is more in the males than the females and the difference is statistically significant.
Studies performed on the lower canines using the ratio between the maximum crown width and canine arc width, resulting in a MCI, have shown an ability to determine gender when performed on 384 females and 382 males of the South Indian population in the age group of 15-21 years with an accuracy of 84.3% in males and 87.5% in females by comparing the observed MCI with a standard MCI value.  In a similar study by Muller et al. the population involved the students enrolled in the University of Nice-Sophia Antipolis 210 girls and 214 boys were randomly sampled. The results were found to be statistically significant. In the present study, both these parameters as measured in males and females were compared and the difference was found to be statistically significant.
For molar odontometrics, the comparison of mean values of parameters measured between males and females showed statistically significant differences with P < 0.05 in the MD dimensions of mandibular first molars and these results were in agreement with the studies done by various researchers ,, in which they have observed that the males had larger teeth than females in all the dimensions.
A high level of sexual dimorphism of 5.9% was found for the right side and 4.4% for the left side in the MD dimension of the mandibular molar. This variation in the magnitude of dimorphism can be a result of various factors. Some authors have explained that such a variation could be due to environmental influences on tooth size. A variation in food resources exploited by different populations has been explained as one such environmental cause. Others have suggested the interference of cultural factors with biological forces.  According to Garn et al. teeth have behaved in many ways through the course of evolution, ranging from reduction of the entire dentition to reduction of one group of teeth in relation to another.
Univariate analysis of the study showed that statistically significant dimorphism was obtained in MD dimensions of mandibular first molar. The mean value of these dimensions in male dentition was greater than those of the females.
In the present study, the MD dimension of right and left mandibular first molar showed 67.5% and 70.5% accuracy respectively in determination of sex correctly.
The overall accuracy of sex determination by MCI and mandibular molar odontometrics ranged from 56% to 84% in the current study which is in accordance with the study conducted by Iscan and Kedici  where the canines could correctly classify the sex by 77%. This wide range of accuracy suggests that both these teeth should be used as an adjunct to each other for greater accuracy in determining sex.
It is important to emphasize that although the accuracy of sex determination increases when a multivariate analysis is done using combination of values for all first molars but in the present study a univariate analysis on molars was found to be equally informative in determination of sex. The preference of univariate analysis over multivariate analyses for sex determination in the present study highlights the importance of situations when only a single molar is available for examination.
On the whole, the study concludes that the sexual dimorphism of teeth is population specific and among the North Indian population, MD dimensions in mandibular canine and first molar can aid sex determination. It is recommended to conduct similar studies on various populations taking greater sample size for further confirmation as such a method of sex determination has its limitations due to variations of this parameter with geographic distribution. Further on, it is inferred that optimal results in dental sex assessment can be obtained when odontometric methods along with skeletal traits are used.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]