Forensic Odontology: A Handbook for Human Identification

By Anshu Nanda and Jaskaran Singh

This concise yet comprehensive book provides conceptual knowledge about forensic odontology in medical, dental, allied and litigation purposes. Written by authors that are highly knowledgeable, experienced and well-established in the field, this handbook lucidly explains basic and advanced components of dental forensics, beginning with anatomical attributes of the tooth, age assessment, dental anomalies and moving ahead to DNA fingerprinting from dental pulp, disaster victim identification from dentures, bite marks and oral autobiography which is a pragmatic approach in identification. Key features: - Gives an insight into basic and advanced aspects necessary to become an expert practitioner in forensic dentistry with a focus on how to provide apt evidence and explanations - Brings out remedial measures for challenges in disaster victim identification which can prove to be very helpful in crisis management - Provides references for further reading This book is intended as a handbook for readers who require a basic exposure to forensic dentistry. It will benefit learners and working professionals in forensic medicine, clinical settings, legal review, litigation, disaster management and allied roles involved in the criminal justice system.

• Language: English
• Publisher: Bentham Science Publishers
• Release date: Jul 18, 2023
• ISBN: 9789815124392

Book preview

Anatomical Attributes of the Tooth

Aman Chowdhry¹, *, Priyanka Kapoor²

¹ Department of Oral Pathology, Faculty of Dentistry, Jamia Millia Islamia, New Delhi, India

² Department of Orthodontics, Faculty of Dentistry, Jamia Millia Islamia, New Delhi, India

Abstract

Anatomical variations in the human species can be attributed to interactions between genetic influences and environmental factors. These variations also permeate dental morphology, and dental morphological traits are of value for understanding variations among populations. Dental anthropologists have cataloged this diversity, and these traits have been used in various disciplines.

To establish population-based data, both metric and nonmetric dental trait frequencies are required. These anatomical attributes have applications in forensic odontology and archaeological contexts. Both nonmetric and metric traits are being used in the fields of dental profiling (assessing age, sex and ethnicity) and bite mark analysis.

A trait that is higher in number in one population may be considered normal in the population. In contrast, if a trait is found at a low frequency, it could inadvertently be considered an anomaly. It can help in determining the relationship with ancestry, which justifies the significance of data pools of dental traits in human forensic identification.

Although numerous studies of dental anatomical landmarks and peculiarities have been carried out in search of population patterns worldwide, India has yet to establish a database for its population. This highlights the need for an area-specific, gender- and ethnicity-based database of dental traits for the population of the Indian continent, which does not exist at present.

Keywords: ASUDAS, Carabelli’s traits, Dental identity, Disaster victim identification.

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* Corresponding author Aman Chowdhry: Department of Oral Pathology, Faculty of Dentistry, Jamia Millia Islamia, New Delhi, India; E-mail: [e-mail]

CONCEPT AND DEFINITIONS

Archaeology and Anthropology

Archaeology: Etymological archaeology is derived from the Greek word archaiologia, where archaio means ancient and logos means study. Thus, archaeology is a branch of science to study, discover and understand skeletons and artifacts that remain left behind by humans.

Anthropology: Etymologically, anthropology is derived from the word anthropos, which means man, and logos, which means study. Thus, anthropology is the branch of science that deals with learning about human and human behaviour and societies in the past and present.

Dental Anthropology

Teeth have a wide array of variables, which are controlled by genes and the environment. The study of these morphological variations in teeth is called dental anthropology.

Dental Trait

Dental traits are distinguishing characteristics, peculiarities, or attributes of a tooth that can be metric and nonmetric in nature (Fig. 1).

Fig. (1))

Dental traits.

These traits help to distinguish the set, arch, class, or type of each tooth, i.e:

Set Traits (Dentition Traits)

Difference in primary and secondary sets of dentitions.

E.g., Difference in deciduous and permanent central incisors.

Arch Traits (Upper and Lower Teeth Traits)

Difference in maxillary and mandibular arch teeth.

E.g., Difference in permanent maxillary central incisor and mandibular central incisors.

Class Traits (Interclass Traits)

Differences in four classes of teeth (Incisor, Canine, Premolar and molars).

Type Traits (Intraclass Traits)

Difference in teeth within one class.

E.g., Difference in central incisor and lateral incisor or difference in first and second premolars.

Arizona State University Dental Anthropology System

ASUDAS is a standard protocol plaque crafted by Scott and Turner in 1991 for objectively scoring more than 30 morphological traits of teeth. They have suggested that unique dental traits have been formed over the years due to genetic and environmental factors that influence various populations. These traits can be consistently reproduced and gauged between observers. For consistency, plaques are utilised; this gives a visual explanation for various traits. A novel web-based application of ASUDAS (i.e., rASUDAS) has been tested on osteological remains excavated from Ptuj, Eastern Slovenia [1].

Carabelli’s Trait (Tuberculum Anomale)

In 1842, the Cusp of Carabelli was one of the most studied traits and was first recorded by Sir George Carabelli [2]. Morphological variation appears on the lingual surface of the mesiolingual cusp of the upper molars (Fig. 2). It presents itself as a fifth separate cusp and is less prominent if present in the upper second and third molars [3, 4]. Bhavya R et al. (2020) found an increased risk for caries in the Carabelli cusp in primary maxillary second molars [5].

Fig. (2))

Cusp of Carabelli.

Shovelling

The occurrence of lingual marginal ridges (mesial and distal) on maxillary or mandibular incisors and canines. These can be slightly developed or very prominently present as well (Fig. 3a and 3b). ASUDAS plaque number 12 is designed for shovelling in the permanent upper incisor, and the plaque classification of shoveling into eight variants (0-7), from none (type 0) to barrel-shaped (type 7). Carayon D et al. (2019) suggested a novel quantitative geometric morphometric method for the quick and effective assessment of shoveling levels in maxillary central incisors [6].

Fig. (3))

Shovelling.

Sexual Dimorphism

This is the systemic distinction in form between individuals of different sexes in the same species. Homosapiens have a low level of sexual dimorphism, in contrast with many species [7].

INTRODUCTION

Teeth are unique, just as people are individuals, Dr. Aman Chowdhry.

Each tooth is specific to a person and has unique traits that distinguish them from each other. The teeth can be distinguished from other teeth, both by intermouth and intramouth analysis. There can be metric (e.g., tooth size, i.e., features based on measurements) and nonmetric traits (e.g., tooth shape, i.e., features based on the presence or absence of some peculiarity). The size, shape, composition, and overall appearance of each tooth attribute specific traits of the teeth. These traits are utilised by experts not only to restore the tooth but also in forensic odontology and archaeological contexts. These traits have applications in dental profiling (assessing age, sex and ethnicity) and bite mark analysis. A trait that is at high frequency in a population may be considered normal in a population, whereas a trait found at low frequency could inadvertently be considered an anomaly [8].

Human tooth shape varies greatly among individuals and populations. In addition, Dental traits can be used in population genetic studies when DNA is not available [9, 10]. Various scientists have worked on the analysis and comparison of various dental traits for various reasons. This chapter explores anatomical attributes/peculiarities/uniqueness of teeth and dentition, which can help a dentist in the forensic context, which includes distinguishing various teeth types and their marks from each other. The anatomical attributes of teeth and dentition can be metric and nonmetric, where metric traits are measurable (e.g., length of root or mesiodistal width of canine) and nonmetric traits are just features that are unique to teeth anatomically (e.g., Cusp of Carabelli, Shovelling).

PARTS OF TOOTH

Any complete tooth can be divided into two parts: Crown and Root. The crown and root of the tooth are separated from each other by a cervical line.

Tooth Crown

This is an anatomical part of teeth covered by the enamel in the crown. The crown can be an anatomical and clinical crown on the basis of the position of the crown in the oral cavity.

Anatomical Crown: Part of the tooth crown is covered by enamel.

Clinical Crown: Part of tooth crown that is visible clinically.

Tooth Root

The anatomical part of teeth covered by cementum is the root. A tooth can be mono-rooted (single root) or multiple-rooted. Single roots are present in anterior teeth (incisors and canines). Multiple roots are seen in premolars and molars. Bifurcation and trifurcation are the terms used when the root is divided into two or three parts.

Fig. (4))

Parts of teeth: Crown and Root.

DENTAL IDENTITY

Dental identity is defined as the total of all characteristics of the teeth and their associated structures which, while not individually unique, when considered together, provide a unique totality [11].

It is said that no two mouths are alike [12]. A total of 32 teeth can generate 1.8 x 10¹⁹ combinations. No minimum count of positive features (trait match/pattern match) has been suggested to derive a positive match for the identity of an individual. A single unique feature or peculiar pattern may be enough to conclude a positive identification match. However, X-rays of the entire mouth may not indicate a positive match [11].

HUMAN TEETH AND DENTITION

Dentition refers to the growth and development of teeth and their arrangement in the oral cavity. Humans’ dentition has two sets of teeth (i.e., Diphyodont), which are embedded in sockets (i.e., Thecodont). The first dentition is the primary dentition (a.k.a. deciduous dentition or baby teeth, or milk teeth), and the second set of dentitions is the secondary set of dentition (a.k.a. permanent dentition or adult dentition). Both sets have different numbers and classes of teeth. The presence of different classes of teeth (incisors, canines, premolars and molars) makes human dentition a Heterodont. Hence, human dentition can be described as:

Diphyodont,

Thecodont and

Heterodont.

NUMBERING SYSTEM OF TEETH FOR DENTITIONS [13-15]

Many dental notation systems are used by dentists to identify/denote each tooth (both deciduous and permanent), similar to the chemical symbols used for representing elements in a periodical table. These systems help in recording relevant dental data under a standard format. The notation system acts as a unique address of teeth and is required for clear communication. Various details about the tooth notation/numbering system are enumerated in Table 1.

The commonly used tooth numbering systems or shorthand systems of teeth are as follows:

FDI World Dental Federation notation

Universal numbering system/American system

Zsigmondy system/Palmer notation method/Grid system

Victor Haderup System

Zsigmondy-Palmer notation system (a.k.a. Military system/Symbolic system/Grid system)

Table 1 Details about tooth notation/numbering systems.

It is the oldest tooth notation system. It has a symbolic representation of quadrants, is user-friendly, is easily adaptable for taking history notes, and is still the notation of choice for teaching purposes in many dental schools and with many private practitioners while taking handwritten notes. The only major limitation is making it conducive for computer applications, as the symbols denoted in this system are difficult to use on computer keyboards. Hence, the digital storage aspect of using this system is extremely limited. Additionally, there is no differentiation in the right upper, right lower, left upper and left lower teeth, and only segments can differentiate. Verbal communication is a major challenge.

Permanent dentition:

Deciduous dentition:

Fédération Dentaire Internationale (a.k.a. ISO 3950 notation system)

This tooth notation is the most widely used system of tooth notation. It represents a two-digit system where the first digit represents the quadrant, in deciduous [5-8], in permanent [1-4], and the second digit denotes the tooth type, deciduous [1-5] and permanent [1-8].

Permanent dentition:

Deciduous dentition:

The advantages include being easily represented verbally, in print, and on computer programs. It uses a specific number representing each quadrant and tooth and is more accurate, easy to teach, and memorise. It may provide a tooth-notation language that is easily communicable and understood, even at the beginner level.

The Victor Haderup tooth system is an extension of the FDI tooth notation system where the positioning of +/- next to a number decides the quadrant of the tooth.

Universal notation system (a.k.a. American system)

It includes a sequence of Arabic numbers (1 - 32) for permanent dentition and an alphabetical system (A-T) for deciduous dentition. The numbering starts from the upper right quadrant, moves clockwise to the upper left and lower left, and finally, the lower right quadrant, both in deciduous and permanent dentition.

Permanent dentition:

Deciduous dentition:

It is mostly used in the United States. Advantages are being computer friendly, as the data are easier to be entered in the digital format due to specific numbers being allotted to specific teeth. However, it is not user-friendly for beginners. It becomes confusing as the number allotted to each tooth is counted in sequence even if not present in the mouth. Additionally, it is not easy to remember the number of each tooth.

Tuzoff DV 2019 proposed an interpretation of radiographs by detecting the tooth and its corresponding notation based on CNN. Their proposed computer-aided diagnosis solution interpretation performance was compared to expert levels [16].

ANATOMICAL DIFFERENCE IN DECIDUOUS AND PERMANENT TEETH

Primary dentition consists of 20 teeth in number, and permanent dentition has 32 teeth (Table 2, where 1.1 is for the Primary Dental Formula and 1.2 for the Permanent Dental Formula). Deciduous teeth resemble corresponding permanent teeth; however, the mandibular first molar is an exception since it does not resemble any tooth of secondary dentition. Anatomical differences between deciduous and permanent teeth are compiled and mentioned in Table 3. These differences can be very useful in dental profiling and bitemark analysis.

Table 2 Dental Formulas for primary and permanent dentition.

Table 3 Anatomical differences in primary and deciduous lesions.

Fig. (5))

Mamelons.

Sujitha P. (2021) in a cross-sectional study on nonmetric traits in primary molars found the frequency of traits to be in descending order of [17]:

1. Metaconule

2. Cusp of Carabelli

3. Deflecting wrinkles

4. Second primary molars

5. Distal trigonid crest

6. Parastyle

COMPARATIVE CHARTING AND ARCH FORM (HUMAN VS ANIMAL)

Homodont have all teeth similar (e.g., reptilian dentition has single cusp teeth that are conical and are used for grasping food objects), whereas Heterodont possesses more than a single tooth morphology (mammalian dentition). Thus, a heterodont can possess incisors, canines, and molars at the same time and is generally omnivorous.

Table 4 enumerates dental formulas of various animals that can be very useful in identifying what animal the skull came from [18]. Additionally, differences in arch forms of human and animal dentition are enumerated in Table 5. A very important part of bite mark investigation is to identify if the bite mark that is being investigated is a human or an animal mark produced by teeth. Anatomical attributes, arch placement and jaw movement dynamics should be performed at length to derive a report.

Table 4 Dental Charting of various animals.

Table 5 Differences in arch forms of human and animal dentition.

DENTAL PROFILING FROM ANATOMICAL TRAITS OF TEETH

Teeth have unique features, such as being hard and resilient to many factors, including chemicals, putrefaction, and fires. The can serve as a durable source of identification with or without comparison with antemortem dental records. Maxillary lateral incisors show the maximum number of variations and can be peg shovel, round, etc.

Dental profiling or dental reconstruction is performed to establish identity when antemortem records are not present. Dental profiling of an individual from teeth comprises assessing age, sex or ethnicity of teeth. We discuss how anatomical attributes of teeth can help in the following:

• Determining age from teeth,

• Determining sex from teeth, and

• Determining ethnicity from teeth.

Dental Age Assessment (DAA) from Anatomical Traits of Teeth

DAA has applications in many disciplines, including paediatric dentistry, orthodontics archaeology, anthropology, forensic science and forensic odontology. Some of the DAA methods include Demirjian's method, Willems' method, Cameriere's method, Nolla's method, Smith's method, Haavikko's method and Chaillet's method [19].

There are two methods of DAA [20]:

Radiography and clinical visualisation of the eruption of teeth.

The clinical method to assess dental age is based on the emergence of teeth in the mouth.

Unique and comparable traits of age-related regressive alterations in teeth along with dental procedures can be used in determining age [21].

Sex Determination from Anatomical Traits of Teeth

Before discussing this topic, it is important to understand the terms sex and gender. They cannot be used interchangeably since they have different meanings. Sex has been defined as ethnic and biological dissimilarity in the human body. Gender is an expression of the exclusive features that a society or culture delineates as masculine or feminine. Therefore, the term sex determination should be used instead of gender determination when identifying the sex of an individual [22].

Odontometric studies have revealed that teeth exhibit sexual dimorphism. Forensic odontologists can assist other experts in determining the sex of the remains using teeth and skull traits [23]. Many anatomically differentiating features have been reported, of which acquired peculiarities such as increased tooth abrasion in males due to comparatively more masticatory forces and certain oral habits that require special attention. However, these methods have the major disadvantage of being subjective and hence have not been proven in sex determination [22].

P. R. da Silva et al. (2019) systematically reviewed the tooth crown sexual dimorphism pattern. Sexual dimorphism of mesiodistal crowns of teeth was found in the following order [24]:

1. Mandibular canines (5.73%)

2. Maxillary canines (4.72%)

3. Mandibular second molars (3.54%)

4. Maxillary second molars (3.20%)

5. Mandibular first molars (3.14%)

6. Maxillary first molars (2.64%).

Canine-based metric studies are useful for sex determination, as canines exhibit a high degree of dimorphism [25-27].

It should be of interest that deflecting wrinkles on the lower first molars and distal accessory ridges on the canines are the most commonly reported morphological traits of teeth, which helps distinguish men from women. Here, DW is the ridge that deflects towards the distolingual cusp and is usually an anatomical attribute present in males. However, DAR is a strong and more common trait seen in females [22].

The sex of an individual can be determined from teeth dimensions by utilising statistical methods, which include logistic regression analysis and discriminant functional analysis.

Ethnicity Determination from Anatomical Traits of Teeth

Routine scientists are dependent on dental anatomical attributes to rely on human dental anatomical traits for the reconstruction of genetic affinities among past populations. This is even more important since teeth along with human skeleton parts are often preserved [1, 28]. Teeth form is considered to be highly heritable and selectively neutral and, therefore, to be an excellent proxy for DNA when none is available [28].

Traditionally, human species are classified into mainly Caucasians, Negroids and Mongoloids races [22]. The significant race types of human species are enumerated in Fig. (6). Determining the race of an individual from teeth/dentition is a