Sex Determination Methods in Forensic Odontology

and Jasdeep Kaur1

(1)

Earth and Life Sciences Vrije Universiteit Amsterdam and ILEWG, Amsterdam, The Netherlands
 
Abstract
Sex determination of skeletal remains is part of forensic investigations. The methods vary and depend on different factors. The only method that can give a totally accurate result uses DNA, but in many cases it cannot be used for several reasons, such as cost. Teeth are excellent material for forensic investigations and can be used in the determination of sex. This chapter focuses on the use of teeth and facial bones in sex determination.

5.1 Introduction

Determining the sex of unknown human remains is the important step in the triad of building a dental profile. Forensic odontology plays an important role in establishing the sex of the victims with bodies damaged beyond recognition due to major mass disaster. Sex can be determined based on data from the morphology of the skull and mandible, soft tissues, and metric features, as well as by DNA analyses of teeth.

5.2 Determining Sex from Craniofacial Morphology and Dimensions

The use of morphological features of the skull and mandible is a common approach used by anthropologists in sexing (Sweet 2001). A number of features are known to show variation between the sexes. The use of multiple features tends to be more accurate when used with young adults and the middle-aged. Williams and Rogers (2006) achieved 96% success in determining the sex using different features of the skull and the mandible. They also observed that using a constant six traits—mastoid, supraorbital ridge, size and architecture of skull, zygomatic extension, nasal aperture, and mandibular gonial angle—the accuracy was 94%. This indicates that craniofacial morphology can be used to determine the sex of skeletal specimen with a high degree of precision. The mandible is the largest and hardest facial bone and keeps its shape better than other bones in the forensic and dental anthropologic fields. It has been reported that of 13 nonmetric items of the mandible, the characteristic that best permitted the sexes to be distinguished was the contour of the lower border of the mandible: Rocker-shaped mandibles predominated in males (68.1%), whereas most females (84.6%) exhibited a straight mandible. In addition, the mental region was shaped differently between the sexes: The shape of the chin in most males was generally bilobate or square (91.7%), whereas the chin in females was either square (45.5%) or pointed (54.5%). In this study, the positive predictive values of male and female were 92.5% and 73.7%, respectively (Hu et al. 2006). Five variables were developed from the complete cranium, vault, face, mandible, and bizygomatic breadth. Dimensions from the complete cranium provided the best accuracy. In the mandible, bigonial breadth was the most dimorphic of the measurements taken. Average accuracies ranged from 80% (bizygomatic breadth alone) to 86% (cranium). Diagnostic accuracy, however, was lower than that obtained from the femur and tibia (Steyn and Iscan 1998). Rai et al. (2007) proposed that five BR criteria of sex determination from mandible parameters such as intercanine distance, intercondylar distance, interlingula (covering inferior alveolar foramen), mesiodistal diameter of mandibular canines, and mental foramen to lingula (covering inferior alveolar foramen). BR criteria for determination of sex reveal that the probability of male sex is 95% if three or more of the dimensions are greater than their deviation values. Krogman’s cranioscopy for sex determination is based on 14 characteristics of the skull (Table 5.1). On the other hand, a modified Krogman’s cranioscopy trait by grading was used to simplify gender classification since it was based on a four-point grade (i.e., 0, smooth; 1, small or rough; 2, medium or rougher; and 3, large or very rough) of only three external characteristics of the skull: supraorbital torus, glabella region, and external occipital protuberance (Krogman and Iscan 1986). These authors conducted a study to evaluate the sexual dimorphism in the cranium and mandible of North Indians using Krogman’s cranioscopy and the modified Krogman’s cranioscopy trait by ­grading (Table 5.2).

Table 5.1

Discrimination of gender
Traits
Male
Female
General size
Large
Small
Architecture
Rugged
Smooth
Supraorbital ridge
Medium to large
Small to medium
Mastoid processes
Medium to large
Small to medium
Occipital area
Muscle lines and protuberance marked
Muscle lines and protuberance not marked
Frontal eminence
Small
Large
Parietal eminence
Small
Large
Orbits
Squared, lower, relatively smaller, with rounded margins
Round, higher, relatively larger, with sharp margin
Forehead
Steeper, less rounded
Rounded, full, infantile
Cheekbones
Heavier, more laterally arched
Lighter, more compressed
Mandible
Larger, higher symphysis, broader ascending ramus
Small, with less corpal and ramus dimensions
Palate
Larger, broader, tends to be U-shaped
 
Occipital condyle
Larger
Small
Teeth
Larger, lower M1 more often cusped
Small, more often 4-cusped
Source: From Krogman and Iscan (1986)
Table 5.2

Discrimination of gender using modified Krogman’s cranioscopy trait by grading in North Indian population
Characteristics
Male (%)
Female (%)
p value
Supraorbital torus
Smooth
6.2
71.3
 
Small
23.3
20.0
 
Medium
35.4
6.0
0.05
Large
34.3
2.7
 
Glabella region
0
0
0.001
Smooth
1.4
68.7
 
Rough
6.2
23.9
 
Moderately rough
13.2
8.7
 
Very rough
80.0
6.7
 
External occipital protuberance
 
0
0.001
Smooth
2
37.3
 
Rough
13.3
51.3
 
Moderately rough
29.3
6.7
 
Very rough
56.4
4.7
 

5.3 BR Regression Equation for Sex Determination

Teeth may be used for differentiating sex by measuring their mesiodistal (MD) and buccolingual (BL) dimensions. Various studies have shown significant differences between male and female permanent and deciduous tooth crown dimensions. In the majority of studies, the canines have consistently shown the maximum sex difference. It has been reported that sex can accurately be determined from maxillary and mandibular canines and mandibular second molar in 77% of cases (Is˛can and Kedici 2003). Canines showed the greatest univariate sex dimorphism, followed by the buccolingual (BL) dimension of maxillary first and second molars in Nepalese (Acharya and Mainali 2007). The mandibular canines are considered to demonstrate high sexual dimorphism among teeth in their mesiodistal width. Maxillary first molars (BL diameter), especially the right side, have a higher sexual dimorphism (8.49% casts, 8.27% intraorally) as compared to the left side and hence help in forensic dentistry during an impacted canine (Rai et al. 2008).
Rai et al. (2004) proposed a regression for sex determination from teeth as follows: Sex =1.528 (Maxillary central incisor B-L) – 1.322 (Premolar B-L) + 1.94 (Maxillary first molar B-L)-0.97 (Canine M-D) + 0.837 (Canine B-L)
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Oct 18, 2015 | Posted by in General Dentistry | Comments Off on Sex Determination Methods in Forensic Odontology
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