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FORENSIC ODONTOLOGY: ORIGINAL ARTICLE
Year : 2021  |  Volume : 33  |  Issue : 2  |  Page : 208-214

Sex Determination by Odontometric Diagonal Measurements Using Discriminant Function


Department of Oral Medicine and Radiology, SDKS Dental College and Hospital, Nagpur, Maharashtra, India

Date of Submission07-Dec-2020
Date of Decision26-Apr-2021
Date of Acceptance13-May-2021
Date of Web Publication23-Jun-2021

Correspondence Address:
Dr. Gunjan V Moon
Department of Oral Medicine and Radiology, SDKS Dental College and Hospital, Nagpur - 441 110, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jiaomr.jiaomr_260_20

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   Abstract 


Introduction: Forensic odontology is one of the most unexplored and captivated branches of forensic sciences. Teeth are far excellent material for the anthropological, genetic, odontogenic, and forensic scenario as the morphology of teeth remains unchanged in extreme environmental conditions even after a long period. Aim and Objectives: The study aims to determine the sex of an individual by odontometric diagonal measurements using discriminant function. The objectives are to measure and compare the diagonal measurements of teeth in males and females using crown diagonal diameters of the permanent dentition and to evaluate their sexual dimorphism. Material and Methods: The study sample included 380 maxillary and mandibular dental casts obtained by alginate impressions of 190 subjects (95 males and 95 females) in the age range of 19–35 years selected from Out patient department of Oral Medicine and Radiology. Mesiolabioincisal-distolinguoincisal (MBDL) and distolabioincisal-mesiolinguoincisal (DBML) measurements of right permanent maxillary and mandibular teeth excluding third molars were taken separately using a digital Vernier caliper. Results: The highest mean tooth dimension of MBDL and DBML in both the jaws is of the first molar. The accuracy rate for males (100% for MBDL and 97.89% for DBML) is greater than females (MBDL 93.68% and DBML 94.21%). The overall accuracy rate of maxillary and mandibular MBDL is greater (96.8%) than DBML measurement (95.8% and 94.8%, respectively). Conclusion: The overall accuracy rate for sex determination is 96.8% for MBDL dimensions. The maxillary and mandibular second premolars are the strongest predictors for sex determination.

Keywords: Distobuccal-mesiolingual measurements, discriminant function, mesiobuccal-distolingual, odontometric diagonal measurements, sex determination


How to cite this article:
Moon GV, Sathawane RS, Chandak RM, Lanjekar AB, Bhakte K, Sukhdeve VA. Sex Determination by Odontometric Diagonal Measurements Using Discriminant Function. J Indian Acad Oral Med Radiol 2021;33:208-14

How to cite this URL:
Moon GV, Sathawane RS, Chandak RM, Lanjekar AB, Bhakte K, Sukhdeve VA. Sex Determination by Odontometric Diagonal Measurements Using Discriminant Function. J Indian Acad Oral Med Radiol [serial online] 2021 [cited 2021 Jul 29];33:208-14. Available from: https://www.jiaomr.in/text.asp?2021/33/2/208/319073




   Introduction Top


Forensic dentistry plays a crucial role in the identification of humans during natural calamities and manmade disasters. Based on the recognition of distinct features present in an individual's dental structures, it helps in the identification of living and dead persons.[1] The establishment of gender is an essential step in reconstructing biological profiles from remains utilizing tooth dimensions, craniofacial morphology, and DNA analysis.[2],[3] Teeth dimensions play a vital role in sex determination in young individuals where secondary sexual characteristics are underdeveloped.[4],[5],[6] In natural disasters, the dentition is often preserved due to its physical characteristics.[7],[8],[9],[10],[11]

Various odontometric methods used for sex determination are mandibular canine index and width measurements.[11],[12] Crowding, abrasions, attrition, interproximal facets, and calculus in the cervical third pose problems in taking accurate width measurements. In such cases, diagonal measurements have an advantage over width measurements.[11],[13] Therefore, the present study is designed to determine gender using diagonal measurements.


   Materials and Methods Top


The study comprised 190 subjects in the age range between 19 and 35 years.The sample size is derived considering the predictive accuracy of permanent dentition in sex determination as to the main outcome measure from the following assumption from the study of Vodanovic et al.[8]

  1. Anticipated predictive accuracy = 86%
  2. Confidence interval = 95% (α =5%)
  3. Relative precision = 10%


Required sample size n = 185

Included study sample size n = 190 subjects.

Therefore, total sample sizen190 subjects (95 males and 95 females) will be included in the study n=z2 p (1-p)/d2

z= 1.96

therefore z2 = 3.84 approximately 4

p= 0.86

1-p= 0.14

d= (0.10 x 0.86) where z= standard normal value for α=5%

The sample subjects were selected by convenience sampling from the outpatient department of Dental College and Hospital, Nagpur. Subjects fulfilling the inclusion and exclusion criteria were selected by simple random sampling, namely, fully erupted teeth from right permanent central incisor to right second molar, no fillings, no crowns/missing teeth, no crowding of teeth, no fractured teeth, no orthodontic appliances, and no developmental anomalies that could affect odontometric measurements. The study was approved by the Institutional Ethics Committee vide no. SDKS/PG/Syn/OMR/1/21/2017. We followed the ethical principles as per Helsinki declaration. The written informed consent was obtained from the subjects willing to participate in the study. Subjects were divided into two groups which are as follows:

  1. 95 males between 19 and 35 years of age.
  2. 95 females between 19 and 35 years of age.


Upper and lower jaw impressions were taken with alginate impression material followed by the preparation of models with dental stone and casts that were labeled by putting Out Patient Department registration number (OPD) number. For subsequent procedures, the observers were single-blinded. Using these casts, mesiobuccal-distolingual or mesiolabioincisal-distolinguoincisal (MBDL) and distobuccal-mesiolingual or distolabioincisal-mesiolinguoincisal (DBML) measurements of seven right permanent teeth (incisors, canine, premolars, and molars) of each jaw were taken using a digital Vernier caliper.

The following points are defined by Hillson et al.[14] were considered as a guide during the measurements while placing the caliper parallel to the occlusal or incisal surface:

  • MBDL: The largest distance between the mesiobuccal corner of the cementoenamel junction point and the distolingual corner.
  • DBML: The largest distance between the distobuccal corner of the cementoenamel junction point and the mesiolingual corner.


The collected data were subjected to statistical analysis using the SPSS software version 24.0. For the determination of the size of the tooth, the mean and standard deviation were calculated. An independent sample t-test was used to compare mean tooth sizes. Canonical discriminant function analysis was performed to develop a formula to find out the accuracy of various parameters to determine sex. Group centroids/coefficients were the mean discriminant score for each sex. Discriminant function score was calculated using an unstandardized coefficient. To assess the sex, tooth dimensions were multiplied with the respective unstandardized coefficients and added to the constant with the help of the following formula:

that is, y = a + b (x)

where x is the dimension of the tooth in millimeters, a is the constant of function, and b is the unstandardized coefficient of that specific tooth.

If the value was greater than the sectioning point, the individual was identified as a male and if the value was less than the sectioning point, the individual was a female.

For calculating the percentage of sexual dimorphism, the following equation was used:

Percentage of sexual dimorphism = [(xm/xf) -1] × 100

where xm is the mean tooth dimension in males and xf is the mean tooth dimension in females.

P value ≤ 0.05 was considered for significance.


   Results Top


The present study consisted of 190 randomly selected healthy subjects of whom 95 were males and 95 were females.

[Table 1] shows descriptive statistics and percentage dimorphism for maxillary and mandibular MBDL dimensions in males and females. In comparison, the highest percentage of sexual dimorphism for maxillary MBDL measurement was 32.88% observed in the first premolar followed by 32.3% in the second premolar, and the lowest 5.2% seen in the central incisor. The highest mean dimensions observed for maxillary MBDL was 12.12 mm in male and 10.53 mm in female for the first molar. The lowest mean dimensions observed for maxillary MBDL was 6.56 mm in male and 6.06 mm in female for lateral incisor. The P value for all seven teeth was found highly significant.
Table 1: Descriptive statistics, % sexual dimorphism, and t value for MBDL dimensions

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In comparison, the highest percentage of sexual dimorphism for mandibular MBDL measurement of 27.33% was seen for second premolar and lowest percentage of 12.25% for lateral incisor. The highest mean dimension for mandibular MBDL was 11.69 mm in males and 10.06 mm in females for the first molar. The lowest mean dimension for mandibular MBDL is 5.93 mm in males and 5.09 mm in females for central incisors. The P value for all teeth was found highly significant.

[Table 2] shows a comparison of mean DBML dimensions among males and females. In comparison, the mean dimension for maxillary DBML with highest percentage of sexual dimorphism of 36.52% was observed in the second molar and the lowest 11.15% in lateral incisor. The highest mean dimension for the maxillary DBML was 11.34 mm in males and 8.76 mm in females for the first molar. The lowest mean dimension for maxillary DBML was 6.58 mm in males and 5.92 mm in females for lateral incisors. The P value for all teeth was found highly significant.
Table 2: Descriptive statistics, % sexual dimorphism, and t for DBML dimensions

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In a comparison of mean dimensions for mandibular DBML, the highest percentage of sexual dimorphism was 28.17% observed in the second premolar and lowest percentage 7.09% in lateral incisor. The highest mean dimension for mandibular DBML was 11.08 mm in males and 9.84 mm in females for the first molar. The lowest mean tooth dimension for mandibular DBML was 5.60 mm in males and 5.06 mm in females for central incisors. The P value was found statistically highly significant for all teeth.

[Table 3] shows a comparison of mean maxillary and mandibular MBDL dimensions. In comparison, it was observed that the mean dimension of maxillary MBDL was greater than the mandibular MBDL. The highest mean dimension of maxillary MBDL was 11.33 mm and mandibular MBDL was 10.87 mm observed in the first molar. The lowest mean dimension of maxillary MBDL was 6.31 mm seen in the lateral incisor and mandibular MBDL was 5.51 mm seen in the central incisor. The P value for the second molar was found statistically not significant.
Table 3: Comparison of mean dimensions among all subjects for maxillary and mandibular MBDL

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[Table 4] depicts a comparison of mean dimensions for maxillary and mandibular DBML. In comparison, it was observed that the mean value of maxillary DBML was greater than the mean value of the mandibular DBML except for the first and second molars. The highest mean dimensions were 10.05 mm and 10.45 mm observed in the first molar for maxillary and mandibular DBML, respectively. The lowest mean DBML was 6.25 mm seen in the maxillary lateral incisor and 5.31 mm in the mandibular central incisor. The P value for all teeth was found highly significant.
Table 4: Comparison of mean dimensions among all subjects for maxillary and mandibular DBML

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[Table 5] illustrates the canonical discriminant function coefficient for MBDL. Maxillary second premolar (0.468) was the strongest predictor to determine sex followed by first premolar (0.378), canine (0.238), second molar (0.217), and lateral incisor (0.005) which were the next important predictors for sex determination, whereas central incisor (−0.435) and first molar (−0.060) were found less successful predictors. For mandibular MBDL, the second premolar (0.543) was the strongest predictor to determine sex followed by canine (0.326), central incisor (0.271), first molar (0.267), second molar (0.070), and lateral incisor (0.048), whereas first premolar (−0.124) was found less successful predictors.
Table 5: Canonical discriminant function coefficient for maxillary and mandibular MBDL

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[Table 6] shows the canonical discriminant function coefficient for DBML. Maxillary first premolar (0.561) was the strongest predictor to determine sex followed by second molar (0.238), lateral incisor (0.188), first molar (0.175), and canine (0.005), whereas central incisor (−0.409) and second premolar (−0.009) were found less successful predictors.
Table 6: Canonical discriminant function coefficient for maxillary and mandibular DBML

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Mandibular second molar (0.561) was the strongest predictor to determine sex followed by second premolar (0.501), central incisor (0.241), lateral incisor (0.113), first premolar (0.094), and first molar (0.015), whereas canine (−0.197) was found less successful predictor.

[Table 7] depicts the accuracy rate of sex determination from MBDL dimensions. Hundred percent males and 93.68% females were correctly classified with an overall accuracy of 96.8%. This demonstrates that a greater percentage of males were correctly identified using dimensions of both maxillary and mandibular MBDL.
Table 7: Accuracy of sex determination with dimensions of maxillary and mandibular MBDL

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[Table 8] shows the accuracy of sex determination from DBML dimensions. About 98.95% males and 94.74% females were correctly classified by maxillary DBML dimensions with an overall accuracy of 95.8%. This suggests that a greater percentage of males were correctly identified by maxillary DBML dimensions.
Table 8: Accuracy of sex determination with dimensions of maxillary and mandibular DBML

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About 96.84% of males and 93.68% of females were correctly classified by mandibular DBML dimensions with an overall accuracy of 94.8%. This suggests that a greater percentage of males were correctly identified by mandibular DBML dimensions.


   Discussion Top


Teeth are considered a particular organ as their durability even with fire or blast and microbial decomposition makes them indispensable in forensic investigations.[15] Identification of sex from skeletal remains is an important step in establishing the biological profile which helps to recover the ante-mortem records for comparing or constructing an identity and to search files of missing persons.[16]

There are two methods of gender identification using dental characteristics: metric and nonmetric methods. Metric methods depend on tooth dimensions.[17] Nonmetric methods depend on the existence of specific morphological features like the cusp of carabelle, upper incisor shoveling, hypocone, and protostylid which can be employed for the identification of population group.[18]

The coronal morphology and dimensions of the permanent tooth may get affected in conditions such as nutritional deficiency, inherited disorders, and other pathological conditions, but they remain unchanged during normal growth and development. Hence, odontometric features can be used in determining the sex after the tooth has erupted.[19],[20]

The difference in the size of teeth is attributed to the alterations in the hormonal production between the sexes consequent to the differentiation of either male or female gonads during the sixth or seventh week of embryogenesis rather than any direct effect of sex chromosomes.[21],[22] The male teeth are usually larger as compared to females, due to the presence of relatively more dentin in the crowns of male teeth and modulation of enamel thickness regulated by the X chromosome resulting in sexual dimorphism.[2],[23],[24] Hillson et al.[14] emphasized that diagonal measurements are as reliable as width measurements and thereby remain a promising method for sex determination.

In the present study, males showed greater MBDL and DBML dimensions as compared to females. On comparison of MBDL and DBML dimensions, it was found to be statistically highly significant except for maxillary and mandibular MBDL diagonal measurement for the second molar which was not statistically significant.

The gender was determined by multiplying tooth dimensions with the respective unstandardized coefficients and adding to the constant in the formula as mentioned in the “Material and Method” section.

The accuracy rate for maxillary and mandibular MBDL was 100% and 93.68% for males and females, respectively, with an overall accuracy rate of 96.8%. The accuracy rate of maxillary DBML was 98.95% and 94.74% for males and females, respectively, whereas the accuracy rate of mandibular DBML was 96.84% and 93.68% for males and females, respectively. The overall accuracy rate of maxillary and mandibular DBML was 95.8% and 94.8%, respectively. This suggests that maxillary and mandibular MBDL dimensions are showing more sexual dimorphism between the sexes. Similar observations were reported by Peckmann et al.,[25] Zorba et al.,[26] and Rai et al.[27].

Limitations and future prospects

Taking diagonal measurements has got certain limitations as the measurements might go wrong if the caliper is not positioned properly parallel to the tooth axis and require more attention while taking measurements. The method used in the present study “odontometric diagonal measurements” is simple, easy to perform, and inexpensive. The overall accuracy rate of sex determination is found highest. Hence, it is recommended that this method should be applied in future forensic investigations in establishing the identity of a person from fragmented jaws and dental remains.


   Conclusion Top


  • Diagonal measurements of all the seven teeth of males were greater than that of females, thus exhibiting sexual dimorphism between the sexes.
  • The overall accuracy rate of 96.8% for MBDL and 95.3% for DBML suggest that MBDL dimensions determine better sexual dimorphism between the sexes.
  • The maxillary and mandibular second premolars are the strongest predictors to determine sex by both MBDL and DBML dimensions.
  • Maxillary second molar is the next strongest predictor to determine gender by DBML dimensions.


Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient (s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8]



 

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