Odontometric Analysis of Permanent Mandibular Canine to Determine Sexual Dimorphism: A Preliminary Study

Introduction: Crown diameters of a teeth are reasonably accurate predictors of sex and are good adjuncts for sex determinations. The aim of the study was to determine the reliability of mesiodistal width of mandibular canine in sexual dimorphism. Materials and methods: Medical students of Nepalgunj Medical College, Chisapani, Banke, Nepal were selected for data collection. Sample consisted of 300 subjects which included 150 males and 150 females of age group 18-25 years. The mesiodistal width of the mandibular right and left canine teeth were recorded by Vernier calliper. Descriptive statistical analysis was done from odontometric measurements data to calculate sexual dimorphism for mandibular right and left canine. The student t-test was used to determine the level of significance among the parameters measured. Results: The mean values for mesiodistal width of mandibular right canine for male and female subjects were 7.1665±0.28576 and 6.3777±0.37875 respectively. The sexual dimorphism for mandibular right canine was calculated to be 12.368%.The mean values for mesiodistal width of mandibular left canine for male and female subjects were 7.3875±0.35506 and 6.2847±0.41115 respectively. The sexual dimorphism for mandibular left canine was calculated to be 17.5%. Conclusion: Statistical analysis showed significant sexual dimorphism in odontometric analysis of permanent mandibular canines between male and female with the mandibular left canine showing the highest percentage.


Introduction
S exual dimorphism refers to the diff erences in size, stature and the appearance between male and female in relation to various structures of the human body. The skeleton as a whole in general and individual bones such as vertebrae, especially the fi rst cervical (or Atlas) vertebra, sacrum, pelvis, clavicle in particular have been reported to be of great signifi cance in relation to the sex diff erences in various population. Odontometric analyses have also been reported to be of immense value for sex identifi cation because no two mouths are alike 1 . In cases of mass disasters, where there are no personal items of the victims, or the circumstances of the accident destroys soft tissue of body that might help us for identifi cation of the individual; we can use techniques such as facial reconstruction; use of diff erent laboratory procedures of bones and identifi cation from DNA study etc. But of all morphological structures including human skeleton there is only one structure that does not change in size or shape after the initial development that is the teeth.
In the process of identifi cation of skeletal human remains subjected to deterioration by chemical or physical agent, teeth play a fundamental role 2 . Teeth have been identifi ed to show extreme durability because of being the hardest as well as chemically the most stable tissues in the body. The permanent canines off er defi nite advantages as: they are less aff ected by periodontal diseases, are the least extracted ones, are exposed to less plaque, show minimal abrasion from brushing and are the last teeth to be extracted with advancing age 3 . The above causes led earlier workers to use measurements of mesiodistal and buccolingual width of practically all human teeth in the assessment of the sexual dimorphism in world-wide population. Mandibular canines are regarded to show the greatest sexual dimorphism amongst all teeth 4,5 .
Studies on the mandibular canines by earlier workers 5-9 indicated them as key teeth for personal identifi cation of individuals. Teeth in general, have been reported to be larger in size in males when compared with those of female [10][11][12][13][14][15] .
Only scanty reports are available on the abovementioned dental measurements and associated indices in Nepalese population. Hence, the present work related with the mesiodistal widths of the mandibular canine would be of great importance for comparison with the data analysed by the earlier workers in non-Nepalese subjects.

Materials and Methods
This cross-sectional study was conducted in Nepalgunj Medical College, Department of Anatomy after the approval from the ethical review board. Duration of study was 12 months. Medical students of Nepalgunj Medical College, Chisapani, Banke, Nepal were selected for data collection. Each individual was informed regarding objective and method of the study and written consent was obtained from them. Personal informations regarding name, age and sex were recorded. The resultant study sample consisted of 300 subjects which included 150 males and 150 females of age group 18-25 years.
Inclusion criteria of the subjects were medical students of Nepalgunj Medical College between ages of 18-25 years, with healthy anterior teeth free of any pathology, with standard over-jet and overbite (between 2 to 3 mm) and absence of spacing and rotation in anterior region of the jaw.
Missing anterior teeth on either side with prosthesis on concerned teeth and past history of any trauma/ surgical treatment on the concerned teeth were excluded in this study.

Measurement of Mesiodistal width
Each individual was asked to sit comfortably on a chair. Intraoral examination of the anterior mandibular teeth was done to detect occlusion, over-jet, overbite, and rotation and/or malpositioning. The mesial and distal surfaces of right and left mandibular canine were identifi ed (fi gure 1) and the distance between the crests of the curvature on the mesial and distal surface was recorded by Vernier caliper (fi gure 2).

Calculation of Sexual dimorphism
From the above obtained odontometric measurements, sexual dimorphism for right and left mandibular canine was calculated by using following formula 17 .
Where, X m = mean mesio-distal width in males: X f = mean mesio-distal width in females.

Statistical Analysis
Descriptive statistics were calculated from the obtained measurements and indices. For each parameter the diff erences between the means for the male and female were assessed for statistical signifi cance by using SPSS version 16 at the p=< 0.05 level of signifi cance. The student t-test was used to determine the level of signifi cance among the parameters measured.

Mesiodistal width of Mandibular Right Canine:
The mean mesiodistal width of mandibular right canine for male and female subjects (Table1) were 7. 1665±0.28576 and 6.3777±0.37875 respectively. The mean value for total sample was 6.7721±0.51794. Independent t-test revealed p>0.001, which was statistically highly signifi cant. The sexual dimorphism for mandibular right canine was calculated to be 12.368%.

Mesiodistal width of Mandibular Left Canine
The mean mesiodistal width of mandibular left canine for male and female (

Discussion
Gender determination in damaged and mutilated dead bodies or from skeletal remains constitutes the foremost step for identifi cation in medicolegal examination and bioarchaeology. Whenever it is possible to predict sex, identifi cation is simplifi ed because the missing person of only that sex need to be considered 18 .
Although DNA profi le give accurate results, yet odontometric parameters has to be used for determination of sex in a large population because of being simple, reliable, cost eff ective and easy.  There are diff erences in odontometric features in specifi c population, even within the same population in the historical and evolutional context, it is necessary to determine specifi c population values in order to make identifi cation possible on the basis of dental measurements 19 . Doris et al have indicated that early permanent dentition provide the best sample for tooth size measurements because early adulthood dentition has less mutilation and attrition 20 . Consequently, the eff ect of these factors on the actual mesiodistal width would be minimum. Thus only subjects in the 18-25 years age group were included in the study sample. Most commonly, the width and length of the crown were taken in consideration, among this former is considered to be more reliable 21 .
In the present study, the mean values for mesiodistal width was found to be 7.16±0.28mm in males and 6