Sex estimation using diagonal diameter measurements of molar teeth in African American populations

Estimation of sex assigned at birth using dental crown and cervical measurements in a modern global sample

Despite developing prior to the appearance of secondary sexual characteristics of the skeleton, the permanent dentition exhibits sexual dimorphism. Therefore, teeth can serve as a means to estimate sex assigned at birth even in young individuals. This project takes a large global sample of maximum dimensions of the crown as well as measurements of the crown at the cervix to explore sexual dimorphism. Dimorphism is noted in teeth throughout the dental arcade, particularly in the canines. We provide sectioning points as well as the probability of correct classification (ranging from 50.9% to 81.3%) for each measurement to aid the practitioner in sex estimation from the dentition. This research provides a method to estimate sex without arbitrary population specifications. We argue for a global approach that incorporates more population variation to remove the need to estimate "ancestry," (which in actuality is translated to a social race category) and therefore does not force sexual dimorphism-related variation into these mutable and ambiguous categories. Further, this paper demonstrates the utility of the dentition as an additional indicator to aid with the estimation of sex assigned at birth in forensic anthropology. The goal of this research is to better understand the expression of sexual dimorphism across the skeleton in a global context.

How teeth can be used to estimate sexual dimorphism? A scoping review

INTRODUCTION

Teeth are biological structures with a high degree of hardness, density, calcification, and capacity to adapt to extrinsic factors at physical, biological, and physiological levels. Subsequently, they resist for a longer period in deteriorating environmental conditions. With dental analysis, it is possible to acquire biographical data about a person. The aim of this scoping review was to identify publications using human teeth tissues to estimate sexual dimorphism.

METHODS

The scoping review was carried out in the following databases: Jstor, Scielo, Science Direct, PubMed, and Scopus, using ten search strategies in English and guaranteeing completeness and reproducibility of the phases stipulated in the PRISMA guide.

RESULTS

143 studies on sexual dimorphism based on dental tissue traits were included, of which 40.6% (n = 58) were done in Asia and 27.2% (n = 39) in America. 80% of the studies (equivalent to 114 articles) focused their observations and measurements on the dental crown; 4.2% in enamel, dentin, and pulp together; 3.5% in dental pulp; 2.1% in the entire tooth; 2.8% in enamel, root, and the enamel-cementum junction, and only 0.7% in dentin and pulp. In addition, 92.3% of the studies used metric methods, while only 4.9% and 2.8% used biochemical and non-metric method respectively.

CONCLUSION

For sexual dimorphism establishment, enamel has been the most analyzed dental tissue in permanent canines and molars mainly. Likewise, the most widely and accurately used methods for this purpose are the metrics, with the odontometry as the most implemented (intraoral or by using dental plaster models, digital scanning or software) with prediction percentages ranging from 51% to 95.9%. In contrast to biochemical methods, that can achieve the highest precision (up to 100%), the non-metric methods, to a less extent, reported prediction percentages of 58%.

Accuracy comparison of tooth volume and mesiodistal diameter measurements for sex dimorphism based on cone-beam computed tomography: a study for the northern Chinese population

Sex estimation based on teeth could help to narrow the scope for individual identification. According to the different teeth morphology among both genders, we plan to establish a sex estimation method for the northern Chinese population through mesiodistal diameter and teeth volume measurements and compare the accuracy of the two methods. In this study, measurements were taken from cone-beam computed tomography images collected from 142 males and 140 females aged 21-59 years. The mesiodistal diameter and volume of the left canines and the first molars in both upper and lower jaws were measured and analyzed for suitable coefficients. We selected 80% samples as the training set to set up the logistic regression formulas and 20% as the test set to obtain accuracy. The accuracy of sex estimation by mesiodistal diameter can reach 87.50%, and the volume is up to 78.57%. The measurement of mesiodistal diameter is less time-consuming. This work established and tested a method to estimate sex for the northern Chinese population. Results showed that sex estimation based on the mesiodistal diameter of teeth has higher accuracy than the method based on teeth volume.

Automatic sex estimation using deep convolutional neural network based on orthopantomogram images

Sex estimation is very important in forensic applications as part of individual identification. Morphological sex estimation methods predominantly focus on anatomical measurements. Based on the close relationship between sex chromosome genes and facial characterization, craniofacial hard tissues morphology shows sex dimorphism. In order to establish a more labor-saving, rapid, and accurate reference for sex estimation, the study investigated a deep learning network-based artificial intelligence (AI) model using orthopantomograms (OPG) to estimate sex in northern Chinese subjects. In total, 10703 OPG images were divided into training (80%), validation (10%), and test sets (10%). At the same time, different age thresholds were selected to compare the accuracy differences between adults and minors. The accuracy of sex estimation using CNN (convolutional neural network) model was higher for adults (90.97%) compared with minors (82.64%). This work demonstrated that the proposed model trained with a large dataset could be used in automatic morphological sex-related identification with favorable performance and practical significance in forensic science for adults in northern China, while also providing a reference for minors to some extent.

New Approach to Dental Morphometric Research Based on 3D Imaging Techniques

Recent progress in imaging and image processing techniques has provided for improvements in odontological research in a variety of aspects. Thus, the presented method has been developed precisely in order to assess metrically 3D reconstructions of teeth. Rapidly and accurately obtained data of a wide range and appropriate density are sufficient enough for morphometric studies rather than tooth size assessments which are inherent to conventional techniques. The main contributions providing for holistic and objective morphometric analysis of teeth are the following: (1) interpretation of basic dental morphological features; (2) automated of orientational coordinate system setup based on tooth surface analysis; (3) new tooth morphometric parameters which could not be obtained through application of conventional odontometric techniques; (4) methodological novelty for automated odontomorphometric analysis pipeline. Application of tomographic imaging, which has been used for obtaining 3D models, expands the proposed method potential further through providing detailed and comprehensive reconstructions of teeth. The current study was conducted on unique material from the archaeological site of Sunghir related to the Upper Palaeolithic period. Metric assessments of external and internal morphological layers of teeth were performed in common orientation and sectioning. The proposed technique allowed more profound analysis of Sunghirian teeth which date back to the times of modern human morphology formation.

Sex estimation in a Turkish population using Purkait’s triangle: a virtual approach by 3-dimensional computed tomography (3D-CT)

Sex estimation is considered one of the first steps in the forensic identification process. Morphological and morphometrical differences between males and females have been used as means for morphoscopic and metric methods on both cranial and postcranial skeletal elements. When dry skeletal elements are not available, virtual data can be used as a substitute. The present research explores 3-dimensional (3D) scans from a Turkish population to test a sex estimation method developed by Purkait (2005).

Overall, 296 individuals were used in this study (158 males and 138 females). Purkait’s triangle parameters were measured on computed tomography (CT) scans obtained from both right and left femora of each patient at the Bakirkoy Dr. Sadi Konuk Training Research Hospital (Istanbul, Turkey). Intra- and inter-observer errors were assessed for all variables through technical error of measurements analysis. Bilateral asymmetry and sex differences were evaluated using parametric and non-parametric statistical approaches. Univariate and multivariate discriminant function analyses were then conducted.

Observer errors demonstrated an overall agreement within and between experts, as indicated by technical error of measurement (TEM) results. No bilateral asymmetries were reported, and all parameters demonstrated a statistically significant difference between males and females. Fourteen discriminant models were generated by applying single and combined parameters, producing a total correct sex classification ranging from 78.4% to 92.6%. In addition, over 67% of the total sample was accurately classified, with 95% or greater posterior probabilities.

Our study demonstrates the feasibility of 3D sex estimation using Purkait’s triangle on a Turkish population, with accuracy rates comparable to those reported in other populations. This is the first attempt to apply this method on virtual data and although further validation and standardisation are recommended for its application on dry bone, this research constitutes a significant contribution to the development of population-specific standards when only virtual data are available.

Key points

CT analysis using Purkait’s triangle is a suitable tool for assessment of sex in unidentified individuals.

The best overall estimation rate was achieved with the F11 model, with around 92% of accuracy.

The results suggested 78.4% to 92.6% correct sex identification rates.

More research is needed to expand the sample set and verify the results.

Sex estimation by odontometrics of nonadult human remains from a contemporary Italian sample

OBJECTIVES

The objective was to develop an odontometric technique for sex estimation based on dental measurements from adult individuals, and to evaluate its applicability and reliability for diagnosis of sex of nonadult skeletal remains.

MATERIALS AND METHODS

This study was conducted on the permanent dentition of 132 individuals (70 males, 62 females) from the identified human skeletal collection of the Certosa Cemetery (Bologna, Italy) of the University of Bologna. Binary logistic regression equations were developed based on dental measurements of the permanent teeth of the adult individuals, and these equations were subsequently applied to the permanent dentition of nonadult individuals to estimate their sex.

RESULTS

These data show that the canine teeth of both the maxilla and mandible are the most sexually dimorphic teeth in adults, followed by the mandibular second molar, maxillary and mandibular second and first premolars, and mandibular first molar. These data provided correct assignment of sex in 80.4-94.9% of cases, which depended on the measurements used. Of the 26 nonadult individuals of the experimental sample, sex diagnosis was possible for 22, which represented an applicability rate of 84.6% of the individuals. Comparing the sex of these 22 nonadult individuals estimated by odontometrics with the known biological sex, correct assignment was obtained in 90.9% of cases.

CONCLUSION

As a method of sex estimation, odontometric analysis of permanent dentition can be used successfully for nonadult human skeletal remains in both forensic and archeological contexts.

Deep Neural Networks for Chronological Age Estimation From OPG Images

Chronological age estimation is crucial labour in many clinical procedures, where the teeth have proven to be one of the best estimators. Although some methods to estimate the age from tooth measurements in orthopantomogram (OPG) images have been developed, they rely on time-consuming manual processes whose results are affected by the observer subjectivity. Furthermore, all those approaches have been tested only on OPG image sets of good radiological quality without any conditioning dental characteristic. In this work, two fully automatic methods to estimate the chronological age of a subject from the OPG image are proposed. The first (DANet) consists of a sequential Convolutional Neural Network (CNN) path to predict the age, while the second (DASNet) adds a second CNN path to predict the sex and uses sex-specific features with the aim of improving the age prediction performance. Both methods were tested on a set of 2289 OPG images of subjects from 4.5 to 89.2 years old, where both bad radiological quality images and images showing conditioning dental characteristics were not discarded. The results showed that the DASNet outperforms the DANet in every aspect, reducing the median Error (E) and the median Absolute Error (AE) by about 4 months in the entire database. When evaluating the DASNet in the reduced datasets, the AE values decrease as the real age of the subjects decreases, until reaching a median of about 8 months in the subjects younger than 15. The DASNet method was also compared to the state-of-the-art manual age estimation methods, showing significantly less over- or under-estimation problems. Consequently, we conclude that the DASNet can be used to automatically predict the chronological age of a subject accurately, especially in young subjects with developing dentitions.

Three-dimensionally derived interlandmark distances for sex estimation in intact and fragmentary crania

The skull is the element most frequently presented to forensic anthropologists for analysis yet weathering, corpse maiming, and scavenger activity often result in damage and fragmentation. This fragmentation results in a reduction in the number of traditional calliper derived measurements that can be obtained and subjected to discriminant based analyses for sex estimation. In this investigation, we employed three-dimensional geometric morphometric methods to derive novel interlandmark distance measures across six regions of the cranium including the basicranium, basipalate, zygoma, orbits and the cranium globally to create functions to discriminate sex with high efficacy, even in the event of fragmentation. Forty-five homologous landmarks were digitised across each of 227 (114 males and 113 females) South African crania of European descent (white) sampled from the Raymond A Dart Collection of Human Skeletons, housed in the School of Anatomical Sciences, University of the Witwatersrand, South Africa. A total of 990 interlandmark distances (ILDs) were mathematically derived using Pythagorean geometry. These ILDs were then filtered by region and subjected to both direct and stepwise discriminant function analyses. Discriminant equations where derived for each region and achieved the following average cross-validated sex estimation accuracies: basicranium-74%; basipalate-80.2%; zygomatic-82.4; orbits-71.8%; nasomaxilla-83.7%; global cranium-88.2%. A large number of the ILDs used to derive the discriminant functions are novel, demonstrating the efficacy of geometric morphometric methods and illustrating the need to reassess old methods of data collection using modern methods to determine whether they best capture biological differences. The results of this study provide an invaluable contribution to forensic anthropology in South Africa as it provides an accurate, practical means of assessing sex using fragmentary material that may otherwise have been disregarded. These will undeniable aid in accurate sex estimation and ultimately, victim identification.

A systematic review of odontological sex estimation methods

BACKGROUND

In human identification sex estimation plays an important role in the search for ante-mortem data.

AIM

To systematically review studies describing and testing/validating methods of odontological sex estimation. The set research question was: What odontological sex estimation method is the most accurate?

MATERIALS AND METHODS

An electronic search until November 29th 2016 was performed in 5 databases: MEDLINE/PubMed, Cochrane, SciELO, LILACS and Grey literature. The PRISMA guidelines were used. Studies were assessed and included based on the reported data. In particular data criteria were set regarding the considered population, sample size, age range, sex estimation method, type of statistical analysis and study outcome. The extracted data enabled to classify the included studies. Meta-analysis was used to compare the study outcomes per obtained study group.

RESULTS

The established search string detected 4720 studies. 103 were considered eligible after review of title, abstract and full-text. The odontological sex estimation methods were classified based on dental metric and non-metric measurements (n=65), cephalometric analysis (n=13), frontal and maxillary sinuses (n=5), cheiloscopy (n=4), palatal features (n=3) and biochemical analysis of teeth (n=13). Teeth measurements for sex estimation were mainly performed on casts (n=34), followed by skeletal remains (n=13), medical imaging (n=5), intraoral measurements/ photography (n=4), and cascades of the above (n=4).

CONCLUSION

The variety of published odontological sex estimation methods highlights the importance of sex estimation in human identification. Biochemical analysis of teeth proved to be the most accurate method, but in forensic practice, a need to select the most appropriate evidence based odontological sex estimation method exists.

Odontometric sex estimation from clinically extracted molar teeth in a North Indian population sample

BACKGROUND

Different dental features have contributed significantly toward sex determination in the forensic anthropological contexts. Population-specific standards (discriminant functions or regression formulae) have been suggested for various population groups to identify the sex of an unknown individual from dental dimensions and other odontometric features. The main purpose of the present investigation was to examine the degree of sexual dimorphism exhibited by the human teeth of North Indians and identify importance as a forensic tool in sex determination.

MATERIALS AND METHODS

The linear and diagonal dimensions were recorded at both crown and cementoenamel junction levels of 58 upper and 72 lower molars of 130 Northwest Indian subjects (73 males and 57 females). The measurements were subjected to appropriate statistical analyses to estimate the sex estimation accuracy from lower and upper molars separately.

RESULTS

Univariate analyses revealed that molar teeth had greater dimensions in males than the females and the mesiodistal cervical diameter (MDCV) was found to be the most suitable variable for sex determination of the molars. The classification results were in agreement with the previously conducted studies. The index of sexual dimorphism (ISD) was calculated to be higher in lower molars than the upper molars, and the highest sex differences were observed for MDCV based on the ISD. The overall sex estimation accuracy obtained from multivariate discriminant function analysis and regression analysis of pooled data was 70.0% (74% males, 64.9% females) and 66.9% (78.1% males, 52.6% females), respectively.

CONCLUSIONS

Odontometrics can play a significant role in establishing the biological identity of an unknown individual even from a single tooth in the absence of other sophisticated molecular or biochemical techniques used for this purpose.