| Abstract|| |
Background and Aim: Teeth are excellent material for anthropological, genetic and odontologic investigations in both living and dead population. Canines are the ideal teeth for identification of sex, due to its sexual dimorphism and durability in the oral cavity. This study tests the effectiveness of the canine tooth in predicting sex of an individual.
Materials and Methods: This study involved 60 males and 60 females between the age group of 20-30 years. Mesio-distal (MD) widths of maxillary and mandibular right and left canines and inter-canine distance of both arches were measured clinically and on cast for all patients. Standard canine indices were derived from these dimensions and tested for sexual dimorphism and reliability of canine teeth in gender determination by comparison with the known gender of the population under investigation.
Results: All measurements showed significant sexual dimorphism. Standard mandibular canine index (CI) was found to be more reliable in gender estimation than the MD width of canine and CI values.
Interpretation and Conclusion: Use of the standard mandibular CI in gender determination is recommended for forensic procedures as it was found to have an acceptable accuracy. MD width of canine may be used in a setup when only the single tooth or a fragment of a jaw is available for analysis, with due consideration to its relatively low accuracy.
Keywords: Cuspid, forensic dentistry, gender identity, odontometry
|How to cite this article:|
Paramkusam G, Nadendla LK, Devulapalli RV, Pokala A. Morphometric analysis of canine in gender determination: Revisited in India. Indian J Dent Res 2014;25:425-9
Forensic medicine, plays a major role in identification of dead bodies, which may be required in cases of sudden and unexpected death, fires, explosions, railway or aircraft accidents, mutilated or hidden decomposed bodies, or foul play.  Today, dentist's opinion is respected widely as a source of valuable data that can be used to answer questions that arise during a death investigation. Forensic dentists can use this data to provide significant conclusions.  The only method that can give a totally accurate result is the DNA technique, but in many cases and for several reasons it cannot be used. , An important initial step in identification of the dismembered remains of mass disaster victims is the separation of sexes.  Osteometry is considered the preferred technique because it is more effective in determining sex.  Those bodies, which are less complete and consisting of parts of a skeleton only, present more problems in identification and in many instances may not be identified at all.  In fragmented cranial bones, mandible could be obtained and measurements of canine tooth and the inter-canine distance (ICD) might prove as one of the means of determining sex.  Canines are also better likely to survive severe trauma such as air disasters, hurricanes or conflagration, indicating that mandibular canines can be considered as the key teeth for personal identification. , Various studies have been conducted to test the reliability of canine teeth in gender establishment, but the results are conflicting. Most of the studies have shown a greater mesio-distal (MD) diameter in males compared to females. ,,,,,, Reverse dimorphism has also been shown by some of the studies, ,, and it has been concluded that the finding can be attributable to evolution resulting in a reduction in sexual dimorphism, causing an overlap of tooth dimensions in modern males and females. Furthermore, it has been stated that "the mandibular canine showed a greater degree of sexual dimorphism than the maxillary canine."  However, other investigators, , reported that maxillary canine showed a higher degree of sexual dimorphism compared to the mandibular canine in a Japanese population. Thus, the controversy exists regarding the degree of sexual dimorphism between mandibular and maxillary canine teeth in different ethnic groups. There lies a strong reason for selection of the mandibular canine in most of these studies of odontometry. The mandibular canines are not exposed to less plaque,  calculus,  abrasion from brushing, or heavy occlusal loading than other teeth, but they are less severely affected by periodontal disease,  the least frequently extracted because of periodontal disease, and the last tooth to be extracted in respect to age.  The reason for this increased resistance to damage is not known, but is presumed to be of systemic origin.  This study was undertaken to investigate the reliability of canines in predicting sex and also to compare the role of maxillary and mandibular canines in gender establishment based on the morphometric criteria of canine teeth.
|How to cite this URL:|
Paramkusam G, Nadendla LK, Devulapalli RV, Pokala A. Morphometric analysis of canine in gender determination: Revisited in India. Indian J Dent Res [serial online] 2014 [cited 2019 Aug 21];25:425-9. Available from: http://www.ijdr.in/text.asp?2014/25/4/425/142514
| Materials and methods|| |
The study was conducted in Department of Oral Medicine and Radiology, Kamineni Institute of Dental Sciences, India after approval by the Institutional Ethics Committee. 60 male and 60 female patients between the age group of 18 and 25 years were selected for the study. Inclusion criteria included healthy state of gingiva and periodontium, normal Angle's Class 1 molar-canine relationship, caries free teeth, absence of spacing in the anterior teeth and normal overjet and overbite. Patients with partial anodontia, supernumerary teeth, hypoplastic teeth, teeth showing physiologic or pathologic wear and tear and patients with parafunctional habits were excluded from the study. Measurements of MD widths of the four canines and ICD between the maxillary and mandibular canines were measured clinically [Figure 1] and [Figure 2] using digital Vernier calipers with a resolution of 0.01 mm. Alginate impressions of both maxillary and mandibular arches were taken for all subjects and casts were poured with dental stone. MD widths of the four canines and ICD between the maxillary and mandibular canines were measured on the dental casts using digital Vernier calipers with a least count of 0.01 mm [Figure 3] and [Figure 4]. Clinical measurements were compared with that of cast measurements and found to be almost similar. With the measurements on cast, canine index (CI) was derived as the ratio of the average canine width to the corresponding arch width. Sexual dimorphism was also calculated.  A mean value of the CI was calculated for males and females, which were then used to derive the standard maxillary and mandibular canine indices.
|Figure 1: Measurement of mesio-distal width of canines clinically on the patient|
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|Figure 2: Measurement of inter-canine distance clinically on the patient|
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SCI = (Mean CI of males − SD of males)+(Mean CI of females + SD of females)/2.
Xm = Means of MD width of canine's of males, Xf = Mean of MD width of canine's of females.
SCI = Standard Canine Index, CI = Canine Index, SD = Standard Deviation.
Student's t-test was used to compare the mean difference of all measurements between males and females. The individuals with CI value less than the standard CI (SCI) were designated as females and those with higher values as males. The estimated gender was then compared with the known gender and percentage accuracy of the determination of sex using standard maxillary, and mandibular canine indices were derived.
| Results|| |
This study results suggested that the mean values of all measurements [Table 1] in males were greater compared to females except for the CI and though statistically significant difference was found for all four canines, it was highly significant for left mandibular canine with a P = 0.001. Though the mean values of MD widths of canine and ICD are statistically significant, CI values calculated using them are not statistically significant for both the maxilla and mandible. This statistically insignificant results of CI may be because it is a relative value, and it is obtained as the ratio of two absolute measurements (MD dimension of canines and ICD), and does not reﬂect sex differences that exist in absolute measurements, and these sex differences might have got cancelled because of the division between these absolute measurements.
|Table 1: Mean values of MD dimensions of canines and inter-canine distance and CI of maxilla and mandible and mean difference between males and females |
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Sexual dimorphism was calculated based on MD width of canines and was found to be highest for the left mandibular canine [Table 2].
Standard canine index values for both maxillary and mandibular arches were derived [Table 3] and gender determination was done. Subjects with CI values greater than SCI were considered as males and subjects with CI values less than SCI were considered as females. The percentage accuracy of gender determination using such assumption based on SCI value was calculated [Table 4]. Percentage accuracy using both standard maxillary and mandibular canine indices was >70%. It was also observed that standard mandibular CI value is more reliable than standard maxillary CI value with a higher percentage of (about 78%) accuracy in gender determination. It was also found that the gender prediction in males is more reliable than in females with higher percentage of accuracy (around 78%).
Considering the standard mandibular CI to be more reliable in determining the sex of an individual, the standard mandibular CI values of other similar studies were tabulated and percentage accuracy of gender determination using mandibular CI of other studies on this study data were calculated [Table 5], showed that the standard mandibular CI value of our study was very close to other studies and the percentage accuracy was also found to be >70% except for the standard mandibular CI value derived by Rao et al.
|Table 5: Percentage accuracy of gender determination for the present data using standard mandibular CI value derived from various studies |
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| Discussion|| |
This study results suggested that the MD width of both the mandibular and maxillary canines was significantly larger in males compared to females, consistent with the results of the previous studies, ,,,,,,, in contrast to a study by Al-Rifaiy et al.,  where the differences between males and females were not statistically significant. They also suggested that the canine teeth were bilaterally symmetrical in both arches and found 55% and 65.5% correct classification of females and males respectively using MD canine width and ICD. Whereas our study showed differences between dimensions of right and left canines with greater sexual dimorphism (8.4) for mandibular left canine, a finding in agreement with earlier studies by Kaushal et al.,  Kapila et al.,  showed a statistically significant dimorphism in mandibular canines with 8.8 and 9.7, respectively.
Hashim and Murshid  studied 720 teeth on pretreatment orthodontic casts in a Saudi population aged 13-20 years noticed that the canines were the only teeth to exhibit the dimorphism and also determined that there was no statistically significant difference between the left and right canines, suggesting that measurement of teeth on one side could be truly representative when the corresponding measurement on the other side was unobtainable. 
In contrast to our study, few studies showed reverse sexual dimorphism, where the females show larger teeth than males. Boaz and Gupta  in their study on 100 dental casts of a South Indian population in the age group of 14-20 years, observed that the mean of the buccolingual and MD dimensions of the mandibular left canine and the mean of the MD dimensions of the mandibular right canine in females were greater compared to males without significant statistical difference. Acharya and Mainali  found reverse dimorphism in the MD dimension of mandibular second premolars in a Nepalese population. Yuen et al.  measured MD crown diameters in both primary and permanent teeth in a Chinese population and observed reverse dimorphism in the mandibular incisors. However, their findings were not statistically significant.
Rao et al.  calculated the mandibular CI on a sample of on 384 females and 382 males of the South Indian population in the age group of 15-21 years, found significant sexual dimorphism. Mandibular CI values between males and females, in our study were not statistically significant similar to the study by Acharya and Mainali.  However, the absolute measurements used to derive the mandibular CI, viz. MD dimension of canines and ICD were both signiﬁcantly larger in males (P < 0.01).
Using standard mandibular CI value, Rao et al.  obtained a healthy 85.9% accuracy in sex identiﬁcation. Later, Muller et al.  tested Rao et al.'s standard mandibular CI on a French sample of 210 girls and 214 boys and could correctly identify the sex in just 59.4% of cases. In an attempt to improve the accuracy they derived a separate standard mandibular CI on their sample, which marginally improved sex classiﬁcation to 63%. Considering this improvement, we also derived a standard mandibular CI on our sample and compared its effectiveness of this standard mandibular CI, as well as those derived earlier, in determining sex of our sample [Table 6]. The standard mandibular CI of our study was also close to that derived in the previous studies and proved equally effective in determining sex. The ability of identifying males was slightly higher in our study, similar to a study by Reddy et al.  whereas few studies had relatively high ability to identify females.
|Table 6: Comparing percentage accuracy of gender determination with various similar studies |
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In conclusion, though the results are in agreement with most of the previous studies, the present study has its own limitations. Smaller sample size, single examiner might have resulted in few errors or bias in the dimensions and results. This study measured only linear dimensions because of the simplicity, reliability, and inexpensivity. More accuracy could have been obtained by the application of Moire's topography and Fourier's analysis that however require sophisticated equipment and the use of complex mathematical equations, respectively. Future studies have to include larger sample size, multiple observers to check intraobserver variation and interobserver agreement.
| Conclusion|| |
Left mandibular canine showed significant sexual dimorphism and the standard mandibular CI is a quick and easy method for determining sex with an accuracy of around 70-80%, when the standard for the population is available. It is better to confirm the results by using other methods of determining sex like the morphometric criteria because sex determination using the pelvis and skull bones shows an accuracy of 95% and above,  but the accuracy of mandibular CI in identification of sex have never exceeded 87.5%. Hence, it can only be used as a supplement tool.
| Acknowledgments|| |
We would like to thank Mr. Ramesh, Statistician, Department of Community Medicine, Kamineni Institute of Medical Sciences, Narketpally.
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Revath Vyas Devulapalli
Department of Oral Medicine and Radiology, Kamineni Institute of Dental Sciences, Sreepuram, Narketpally, Nalgonda, Andhra Pradesh
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]