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 Table of Contents  
ORIGINAL ARTICLE
Year : 2019  |  Volume : 5  |  Issue : 3  |  Page : 151-155

Sex determination using mandibular canine among Northeastern Nigerian population


1 Department of Human Anatomy, Faculty of Basic Medical Sciences, Northwest University, Kano State, Nigeria
2 Department of Human Anatomy, College of Medical Sciences, University of Maiduguri, Maiduguri, Borno State, Nigeria
3 Department of Anatomy, Faculty of Basic Medical Sciences, Bayero University, Kano State, Nigeria, Nigeria

Date of Web Publication18-Sep-2019

Correspondence Address:
Saleh Nuhu
Department of Human Anatomy, Faculty of Basic Medical Sciences, Northwest University, PMB 3220 Kano, Kano State
Nigeria
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jfsm.jfsm_7_19

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  Abstract 


Establishing a person's identity is important for both legal and humanitarian purposes. Sex determination is a key characteristic used in the identification of a deceased individual. The aim of this study was to determine sex by using mandibular canines among individuals in the Northeastern Nigerian population. Two hundred and eight individuals (102 men and 106 women) participated in this study. The mesiodistal widths of the mandibular canines and intercanine distances were measured using a vernier caliper and a divider. Step-wise logistic regression analyses were used to determine sex based on mandibular parameters. Male participants had significantly higher mandibular mesiodistal width than female participants. Similarly, the canine index was significantly higher in male participants than in female participants. The mesiodistal width of the left mandibular canine exhibited the highest sexual dimorphism (9.78%) and was the best characteristic for use in determining sex, with an accuracy of 75%. Among the Northwestern Nigerian population, sex can be most accurately determined using the mesiodistal width of the left mandibular canine.

Keywords: Forensic sciences, mandibular canine, Northeastern Nigeria, sex determination


How to cite this article:
Nuhu S, Dalori BM, Adamu LH, Ibrahim I, Aliyu MN. Sex determination using mandibular canine among Northeastern Nigerian population. J Forensic Sci Med 2019;5:151-5

How to cite this URL:
Nuhu S, Dalori BM, Adamu LH, Ibrahim I, Aliyu MN. Sex determination using mandibular canine among Northeastern Nigerian population. J Forensic Sci Med [serial online] 2019 [cited 2019 Dec 16];5:151-5. Available from: http://www.jfsmonline.com/text.asp?2019/5/3/151/267154




  Introduction Top


Determining the sex of individuals involved in traffic accidents, bomb explosions, mass murders, or natural disasters is among the top priorities of a forensic investigator.[1] Forensic identification of human remains is important for reconstructing an individual's profile from unidentified skeletal remains.[2],[3] Teeth are known to resist various forms of postmortem destruction.[4] Crowns of permanent teeth are formed at an early stage of development, and their dimensions remain unchanged during further growth and development, except when specific changes and disorders of functionality, pathology, and nutrition influence the normal dimensions of teeth.[5]

Often, canines are the last teeth to be extracted in older individuals, as they are least affected by abrasion from brushing, bear lesser occlusal loading, and are less affected by periodontal disease.[6] Thus, they are regarded as the “key teeth” for personal identification;[7],[8] this characterization is supported by their high degree of sexual dimorphism among all teeth.[4],[9],[10]

As there are differences in odontometric features within specific populations, it is critical to determine specific population values to facilitate identification on the basis of odontometric measurements.[11] To determine the existence of sexual dimorphism, which is instrumental in sex determination for forensic investigation, and to determine the best predictor of sex based on the mesiodistal dimension of permanent mandibular canines and intercanine distances among men and women in the Northeastern (NE) Nigerian population, the present study evaluated the mesiodistal dimension of permanent mandibular canines and intercanine distances in the NE Nigerian population.


  Materials and Methods Top


Study area

The study was conducted at the University of Maiduguri in the NE region of Nigeria.[12]

Study population

The study population comprised 208 students (102 men and 106 women, 17–35 years of age), at the University of Maiduguri. Individuals were included if they had a complete set of fully erupted, morphologically well-formed, periodontally healthy, noncarious, nonworn, nonhypoplastic teeth, including satisfactorily aligned mandibular teeth. All individuals provided informed consent to participate in the study. Individuals who had carious, restored, or hypoplastic teeth, as well as those who had teeth with prosthesis, attrition, abrasion, and/or mobility, were excluded from the study. This study was approved by the ethical committee of the institution.

Methodology

Collection of biodata

A brief questionnaire (See Appendix) was completed for all participants, with age, sex, nationality, state of origin, measurement of the mesiodistal widths of their mandibular canines, mandibular intercanine distances (MnCDs), and mandibular canine indices (MnCIs).

Safety measures

The sliding vernier caliper (Tresna; Guilin, Guangxi, China) and manual divider (Starrett; Athol, Massachusetts, USA) used in the study were disinfected with chloroxylenol 4.8% after each use.

Mandibular canine width

The maximum mesiodistal dimensions of the two permanent mandibular canines were measured between the anatomic contact points directly on the participant, using a sliding vernier caliper with a resolution of 0.02 mm, held parallel to the occlusal plane in accordance with the method of Gupta et al.[13] If the placement of the sliding vernier caliper was determined to be difficult, a manual divider with a fixing device and very fine tips was used, as shown in [Figure 1]. Subsequently, the divider distance was measured with the vernier caliper.[14]
Figure 1: Measurement of mandibular canine width

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Mandibular intercanine distance

The MnCD was measured as the linear distance between the tips of the right and left mandibular canines when a divider was placed on the tip of the right canine and extended to the left canine, as shown in [Figure 2].
Figure 2: Measurement of mandibular intercanine distance

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Mandibular canine indices and percentage sexual dimorphism

The formula used to calculate the MnCI was based on the method of Rao et al. as follows:[15]



The percentage of sexual dimorphism was calculated using the formula given by Garn et al. as follows:[16]



Where Xm= mean value of male participants, and Xf= mean value of female participants.

Statistical analysis

The data collected were entered in a spreadsheet (Excel 2013, Microsoft Corp., Redmond, WA, USA) and analyzed using SPSS statistical analysis software (version 20, IBM Corp., Armonk, NY, USA). Student's t-test was used to compare differences between the sexes. Sex was predicted based on mesiodistal width, intercanine distance, and mandibular canine index using step-wise binary logistic regression analysis. P < 0.05 was considered statistically significant.


  Results Top


[Table 1] shows that there were statistically significant differences in the mean right mesiodistal mandibular canine width (MnCW) between the male and female participants (8.03 ± 0.65 mm and 7.38 ± 0.56 mm, respectively). Similarly, there was a statistically significant difference between the male and female participants in the mean left mesiodistal MnCW (8.08 ± 0.71 mm and 7.36 ± 0.56 mm, respectively). The right and left mean MnCIs were significantly different between the male and female participants (right MnCI: male participants, 2.88 ± 0.27 mm, and female participants, 2.69 ± 0.30 mm; left MnCI: male participants 2.90 ± 0.29 mm, and female participants, 2.66 ± 0.23 mm).
Table 1: Mean mesiodistal and intercanine widths of mandibular canines in male and female participants using Student's t-test

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Furthermore, the left mesiodistal MnCW showed the greatest sexual dimorphism (9.78%), whereas MnCD showed the least dimorphism (0.79%). Moreover, proportions of sexual dimorphism for right MnCI, right mesiodistal MnCW, and left MnCI were 7.06%, 8.81%, and 9.02%, respectively [Table 2].
Table 2: Sexual dimorphism in mandibular canine measurements between male and female patients

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All logistic regression equations discriminated sex at a rate better than that achieved by chance, with the value of Chi-square ranging from 58.995 to 68.103, P < 0.05. With respect to sex discrimination, left mesiodistal MnCW was the single best predictor of sex with 75% accuracy and a higher level of misclassification (Log2 likelihood = 229.278) than all other equations. However, the percentage accuracy decreased to 73.1% when three variables (left mesiodistal MnCW, right mesiodistal MnCW, and left MnCI) were included in the equation [Table 3].
Table 3: Logistic regression equations for sex discrimination based on mandibular canine measurements

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  Discussion Top


Odontometry has been performed on various tooth groups with the objective of establishing measurements that can serve as standards in dental surgery and forensic odontology.[17] Dental identification involves either a comparative method or postmortem dental profiling. The main advantage involved in the use of dental evidence for identification is that it can be preserved nearly indefinitely after death. The unique patterns of teeth enable the analysis of antemortem and postmortem dental variables.[1]

Various odontometric dimensions have been used for the purpose of sex estimation such as MnCI,[18] the buccolingual dimension of the teeth,[11] and the height of the teeth.[5] Garn et al.[16] studied the magnitude of sexual dimorphism by measuring the mesiodistal width of canine teeth and showed that mandibular canines showed a greater degree of sexual dimorphism than maxillary canines. However, Minzuno [19] reported that maxillary canines showed a greater degree of sexual dimorphism than mandibular canines in a Japanese population. This notable discrepancy in the use of canines for determining sex was presumed to be due to the influence of the Y chromosome, which was not uniform in all teeth. In contrast, the X-linked genetic influence on tooth width was relatively uniform in all teeth.[15] Furthermore, the mean mesiodistal MnCW recorded in this study was similar to that observed in a North Indian population,[13] but greater than those obtained in Egyptian,[20] South Indian,[21] and Croatian populations.[5] This distinction may be due to differences in geographical location, genetic makeup, and dietary habits.

The accuracy of odontometric analysis for gender determination was investigated by Pettenati-Soubayroux et al.[22] who studied sexual dimorphism in the permanent teeth of 146 skeletons dating from 1722 AD in Marseilles. Pettenati-Soubayroux et al. found lower canines to be the most accurate teeth for the analysis of dental sexual dimorphism; they recommended the use of this method to determine sex in fragmentary adult skeletons, immature materials, missing pieces, or ambiguities on postcranial remains in forensic medicine and anthropology.

To predict sex based on body variables, some researchers use discriminate function analysis, whereas others use logistic regression analysis. Shah et al.[23] reported that logistic regression analysis provided greater accuracy than discriminate function analysis. Notably, we used logistic regression analysis to predict sex in the present study. Based on the analysis of sexual dimorphic traits, we found that the left mesiodistal MnCW was the best predictor of sex in the study population. However, ideal variables to predict sex are known to vary among populations, such that region-specific equations are needed.[23]

Although DNA profiles give accurate results, measurements of linear dimensions (e.g., anthropometric or odontometric parameters) can be used to determine sex in a large population because these measurements are simple, reliable, and inexpensive. In the context of several mass murders and occupation of Boko Haram insurgents in the NE region of Nigeria,[24] there is a need of a simple, reliable, and inexpensive method that can be used in the identification of individuals. The present study findings thus can be used in determining sex among individuals in the NE Nigerian population.

Despite the dimorphic nature of the dimensions considered in the study, different measurements can serve as predictors with varying degrees of accuracy. The sex of an individual in NE Nigeria can better be determined using a single mandibular canine tooth variable – left mesiodistal MnCW – with 75% accuracy. Although the 75% accuracy suggests that it could be increased by combination with other variables, the accuracy decreased when other variables were included in the prediction equation. Therefore, the results of this study indicate that left mesiodistal MnCW comprises the best predictor of sex among individuals in the NE Nigerian population. However, this study was limited in that it only assessed individuals aged 17–35 years. Therefore, a degree of caution is needed when attempting to generalize the data obtained in this study to individuals outside of this age range.

Sex determination based on skeletal remains constitutes the most important aspect of identification in the context of medicolegal examinations. This study determined sexual dimorphism and the potential for the use of mandibular canine tooth measurements in the sex determination of individuals in the NE Nigerian population. Among the parameters assessed in this study, left mesiodistal MnCW comprised the best predictor of sex among individuals in the NE Nigerian population.

Acknowledgment

We thank Ryan Chastain-Gross, Ph.D., from Liwen Bianji, Edanz Group, China (www.liwenbianji.cn/ac), for editing the English text of a draft of this manuscript.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.


  Appendix Top


Sample Questionnaire

This is a study on “sex determination using mandibular canine measurements in the Northeastern Nigerian population” which will provide baseline data regarding the population of Northeastern Nigeria. Kindly spare your time, as it will require just a few minutes. Thank you.

Bio Data

Age _____________________________

Gender __________________________

Nationality________________________

State of origin_____________________

Mandibular canine measurements





 
  References Top

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Khangura RK, Sircar K, Singh S, Rastogi V. Sex determination using mesiodistal dimension of permanent maxillary incisors and canines. J Forensic Dent Sci 2011;3:81-5.  Back to cited text no. 2
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    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]



 

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