Odontometrics

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Odontometrics is the measurement and study of tooth size. [1] [2] It is used in biological anthropology and bioarchaeology to study human phenotypic variation. The rationale for use is similar to that of the study of dentition, the structure and arrangement of teeth. There are a number of features that can be observed in human teeth through the use of odontometrics.

Contents

The length and width of teeth are measured from front to back and side to side using calipers. These measurements can be made directly from skeletal material or through dental casts of living humans. [1] The measurements that are reported most commonly are maximum crown length and maximum crown breadth. [3]

Uses of odontometrics

Determining age

Linking to the Past by Kenneth L. Feder states that "Dental development...provides a valuable gauge of the level of physical maturity and age." [4] The first set of teeth, or the lower central incisors, does not begin to appear until the infant is approximately six-and-a-half months old. The rest of the baby teeth, which are called deciduous teeth, will then appear “fairly consistently across the species”, until the child is about two-years-old, when the second upper molars appear; at this point in development, there are twenty teeth in all.

From the age of two-and-a-half until about six years, the deciduous teeth maintain stability, until a set of molars (also called “Six Year Molars”) appear in the lower jaw; these are the child’s first permanent teeth. From this point on, for the approximate next twelve years, the rest of the deciduous teeth will be replaced by all of the permanent teeth. Additional permanent teeth will erupt in the back of the mouth in order to enlarge the mouth. When the process of all permanent teeth coming in is over, the adult mouth will have thirty-two teeth.

The “fairly consistent” rate at which deciduous and permanent teeth appear is relevant because it allows an expert to determine the age of the human. According to Feder, based on odontometrics, “the approximate age of a living child or the age at which a deceased child died can be fairly easily and accurately determined based on which teeth are present, the stage of growth of these teeth, and which teeth have yet to erupt into the mouth.”

Determining sex

Though, when available, more standard approaches to sex identification are used, in times where the archaeological remains are not completely discovered or preserved, odontometrics are used. Because teeth are “made from the most enduring mineralized tissues in the human body”, they are resistant to many types of destruction, including physical, thermal, mechanical and chemical. According to Marin Vodanović et al., “Sex determination using dental features is primarily based upon the comparison of tooth dimensions in males and females, or upon the comparison of frequencies of non-metric dental traits, like Carabelli's trait of upper molars, deflecting wrinkle of lower first molars, distal accessory ridge of the upper and lower canines or shoveling of the upper central incisors”. When analyzing the teeth, one must also take into consideration the differences in odontometric features between different populations, or one may be led to a false conclusion in sex determination. [5]

Several studies have established that on average males have larger teeth than females, although the differences are small and not always statistically significant. [6] [7] [8] The most sexually dimorphic human teeth are the canines, with other teeth showing smaller size differences. [9] [10] Recent research looking at the dental tissues within the tooth crown indicate that male teeth have significantly greater quantities of dentine than females, both absolutely and proportionally, and such differences could be useful in estimating sex. [11] [12]

Determining population

Certain features observed in human teeth can link them to different populations. Teeth exhibit variables with a strong hereditary component that are useful in assessing population relationships and evolutionary dynamics. [3] One example is shovel-shaped incisors, in which individuals have ridges on the inside margins of their front teeth. This trait is most common in East Asian and Native American populations and occurs less frequently elsewhere. Teeth have an important role in chewing food, and different dental pathologies and patterns of tooth wear can indicate kinds of food eaten and other dietary behaviors of certain populations. The measurement and examination of teeth can also exhibit incidental and intentional modifications which reflect the patterns of different cultural behaviors. The process of tooth formation is highly reflective of environment. [1] Developmental defects observed on teeth can provide a general measure of environmental stress on a population. [3]

Odontometrics and human evolution

Denisova Molar.jpg

The study of human variation through odontometrics provides information about the past. Measurements of the teeth and jaws of modern humans are smaller than that of their hominin ancestors. However, examinations of fossil evidence have shown a decrease in the size of the masticatory system that can be mostly attributed to the changes in the dietary habits of the species. Canine teeth are believed to be small in the earliest hominins and the reduction of size continues during the early period. In Modern humans, the first molar teeth are the largest among the molars and the overall tooth size is reduced. In the earliest hominins and archaic hominins, second molars were generally the largest of the molars teeth and the third molars were closer to the size of the second molars. The evolution of human tooth size and the masticatory system are not only related to diet and food processing techniques, they are also related to brain size, bipedalism and speech. [3]

Homo habilis

Between 1.9 million and 1.44 million years ago. The teeth of Homo habilis are generally smaller than those of most australopiths, but are still somewhat larger than those of most living humans. [1]

Homo erectus

Arose 1.9 million years ago. The jaws and teeth of Homo erectus are still large compared to those of modern humans but smaller than those of earlier hominins, particularly the back teeth. Microscopic analyses of the teeth show wear patterns characteristic of extensive meat eating. [1]

Homo heidelbergensis

Between 800,000 and 200,000 years ago. Teeth of Homo heidelbergensis were arranged in the jaw so that they formed a parabolic shape (curved at the front). The teeth were also smaller than those of earlier species but still larger than those of modern humans. Some members of this species possessed a gap called a retromolar space, behind the wisdom teeth at the back of the jaw. [1]

Homo neanderthalensis

Between 130,000 and 28,000 years ago. The Neanderthal face acted to withstand stresses brought about by the use of their relatively large front teeth. The front teeth of Neanderthals are large relative to their back teeth and often show considerable wear, suggesting that they were used as tools. [1]

Applying odontometrics

Sumter jane doe teeth chart.jpg

Forensic investigations

Odontometric studies are also utilized for age and sex determination in forensic investigations. [13] They are often used in the forensic cases along with craniofacial morphology. [13] Teeth are good sources of material for civil and medicolegal identification because they provide resistance to damage in terms of bacterial decomposition and fire when the rest of the body is damaged beyond recognition. [14] Odontometrics play an important role in the determination of sex in young individuals when secondary sexual characteristics have not yet developed. [13]

Mass disasters

When a mass disaster occurs, either natural or man-made, odontology can be used to help identify victims. Some natural disasters include tornadoes, hurricanes, wildfires and floods. Man-made disasters can be either intentional or unintentional and include transportation accidents, chemical spills and explosions. Once a mass fatality occurs, forensic odontologists are called in to conduct dental autopsies on remains and compare ante and post mortem dental records. [15]

Case studies

Odontology has been used in many historical cases of identification in crimes and mass disasters. [15]

1952- In Doyle V. Texas, Doyle was convicted of burglary based on a bite mark left on a block of cheese found at the crime scene. This was the first U.S case to result in a conviction based on bite mark analysis. [16]

Other famous cases using odontometrics include:

See also

Related Research Articles

<i>Paranthropus</i> Contested extinct genus of hominins

Paranthropus is a genus of extinct hominin which contains two widely accepted species: P. robustus and P. boisei. However, the validity of Paranthropus is contested, and it is sometimes considered to be synonymous with Australopithecus. They are also referred to as the robust australopithecines. They lived between approximately 2.9 and 1.2 million years ago (mya) from the end of the Pliocene to the Middle Pleistocene.

<span class="mw-page-title-main">Human tooth</span> Calcified whitish structure in humans mouths used to break down food

Human teeth function to mechanically break down items of food by cutting and crushing them in preparation for swallowing and digesting. As such, they are considered part of the human digestive system. Humans have four types of teeth: incisors, canines, premolars, and molars, which each have a specific function. The incisors cut the food, the canines tear the food and the molars and premolars crush the food. The roots of teeth are embedded in the maxilla or the mandible and are covered by gums. Teeth are made of multiple tissues of varying density and hardness.

<span class="mw-page-title-main">Dentition</span> Development and arrangement of teeth

Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, it is the characteristic arrangement, kind, and number of teeth in a given species at a given age. That is, the number, type, and morpho-physiology of the teeth of an animal.

<span class="mw-page-title-main">Canine tooth</span> Long pointed tooth in mammals

In mammalian oral anatomy, the canine teeth, also called cuspids, dog teeth, eye teeth, vampire teeth, or vampire fangs, are the relatively long, pointed teeth. In the context of the upper jaw, they are also known as fangs. They can appear more flattened however, causing them to resemble incisors and leading them to be called incisiform. They developed and are used primarily for firmly holding food in order to tear it apart, and occasionally as weapons. They are often the largest teeth in a mammal's mouth. Individuals of most species that develop them normally have four, two in the upper jaw and two in the lower, separated within each jaw by incisors; humans and dogs are examples. In most species, canines are the anterior-most teeth in the maxillary bone. The four canines in humans are the two upper maxillary canines and the two lower mandibular canines. They are specially prominent in dogs (Canidae), hence the name.

<span class="mw-page-title-main">Forensic anthropology</span> Application of the science of anthropology in a legal setting

Forensic anthropology is the application of the anatomical science of anthropology and its various subfields, including forensic archaeology and forensic taphonomy, in a legal setting. A forensic anthropologist can assist in the identification of deceased individuals whose remains are decomposed, burned, mutilated or otherwise unrecognizable, as might happen in a plane crash. Forensic anthropologists are also instrumental in the investigation and documentation of genocide and mass graves. Along with forensic pathologists, forensic dentists, and homicide investigators, forensic anthropologists commonly testify in court as expert witnesses. Using physical markers present on a skeleton, a forensic anthropologist can potentially determine a person's age, sex, stature, and race. In addition to identifying physical characteristics of the individual, forensic anthropologists can use skeletal abnormalities to potentially determine cause of death, past trauma such as broken bones or medical procedures, as well as diseases such as bone cancer.

<span class="mw-page-title-main">Forensic dentistry</span> Aspect of criminal investigation

Forensic dentistry or forensic odontology involves the handling, examination, and evaluation of dental evidence in a criminal justice context. Forensic dentistry is used in both criminal and civil law. Forensic dentists assist investigative agencies in identifying human remains, particularly in cases when identifying information is otherwise scarce or nonexistent—for instance, identifying burn victims by consulting the victim's dental records. Forensic dentists may also be asked to assist in determining the age, race, occupation, previous dental history, and socioeconomic status of unidentified human beings.

<i>Gigantopithecus</i> Genus of primate

Gigantopithecus was a genus of ape from roughly 2 million to 350,000 years ago during the Early to Middle Pleistocene of southern China, represented by one species, Gigantopithecus blacki. Potential identifications have also been made in Thailand, Vietnam, and Indonesia. The first remains of Gigantopithecus, two third molar teeth, were identified in a drugstore by anthropologist Ralph von Koenigswald in 1935, who subsequently described the ape. In 1956, the first mandible and more than 1,000 teeth were found in Liucheng, and numerous more remains have since been found in at least 16 sites. Only teeth and four mandibles are known currently, and other skeletal elements were likely consumed by porcupines before they could fossilise. Gigantopithecus was once argued to be a hominin, a member of the human line, but it is now thought to be closely allied with orangutans, classified in the subfamily Ponginae.

Hypodontia is defined as the developmental absence of one or more teeth excluding the third molars. It is one of the most common dental anomalies, and can have a negative impact on function, and also appearance. It rarely occurs in primary teeth and the most commonly affected are the adult second premolars and the upper lateral incisors. It usually occurs as part of a syndrome that involves other abnormalities and requires multidisciplinary treatment.

<span class="mw-page-title-main">Malocclusion</span> Medical condition

In orthodontics, a malocclusion is a misalignment or incorrect relation between the teeth of the upper and lower dental arches when they approach each other as the jaws close. The English-language term dates from 1864; Edward Angle (1855-1930), the "father of modern orthodontics", popularised it. The word "malocclusion" derives from occlusion, and refers to the manner in which opposing teeth meet.

<i>Paranthropus robustus</i> Extinct species of hominin of South Africa

Paranthropus robustus is a species of robust australopithecine from the Early and possibly Middle Pleistocene of the Cradle of Humankind, South Africa, about 2.27 to 0.87 million years ago. It has been identified in Kromdraai, Swartkrans, Sterkfontein, Gondolin, Cooper's, and Drimolen Caves. Discovered in 1938, it was among the first early hominins described, and became the type species for the genus Paranthropus. However, it has been argued by some that Paranthropus is an invalid grouping and synonymous with Australopithecus, so the species is also often classified as Australopithecus robustus.

<span class="mw-page-title-main">Shovel-shaped incisors</span> Possible shape of human incisor teeth

Shovel-shaped incisors are incisors whose lingual surfaces are scooped as a consequence of lingual marginal ridges, crown curvature, or basal tubercles, either alone or in combination.

Dental anatomy is a field of anatomy dedicated to the study of human tooth structures. The development, appearance, and classification of teeth fall within its purview. Tooth formation begins before birth, and the teeth's eventual morphology is dictated during this time. Dental anatomy is also a taxonomical science: it is concerned with the naming of teeth and the structures of which they are made, this information serving a practical purpose in dental treatment.

<span class="mw-page-title-main">Postcanine megadontia</span>

Post-canine megadontia is a relative enlargement of the molars and premolars compared to the size of the incisors and canines. This phenomenon is seen in some early hominid ancestors such as Paranthropus aethiopicus.

<i>Nakalipithecus</i> Extinct species of ape

Nakalipithecus nakayamai, sometimes referred to as the Nakali ape, is an extinct species of great ape from Nakali, Kenya, from about 9.9–9.8 million years ago during the Late Miocene. It is known from a right jawbone with 3 molars and from 11 isolated teeth. The jawbone specimen is presumed female as the teeth are similar in size to those of female gorillas and orangutans. Compared to other great apes, the canines are short, the enamel is thin, and the molars are flatter. Nakalipithecus seems to have inhabited a sclerophyllous woodland environment.

<i>Lufengpithecus</i> Extinct genus of primates

Lufengpithecus is an extinct genus of ape, known from the Late Miocene of East Asia. It is known from thousands of dental remains and a few skulls and probably weighed about 50 kg (110 lb). It contains three species: L. lufengensis, L. hudienensis and L. keiyuanensis. Lufengpithecus lufengensis is from the Late Miocene found in China, named after the Lufeng site and dated around 6.2 Ma. Lufengopithecus is either thought to be the sister group to Ponginae, or the sister to the clade containing Ponginae and Homininae.

<span class="mw-page-title-main">Sexual dimorphism in non-human primates</span>

Sexual dimorphism describes the morphological, physiological, and behavioral differences between males and females of the same species. Most primates are sexually dimorphic for different biological characteristics, such as body size, canine tooth size, craniofacial structure, skeletal dimensions, pelage color and markings, and vocalization. However, such sex differences are primarily limited to the anthropoid primates; most of the strepsirrhine primates and tarsiers are monomorphic.

Serial extraction is the planned extraction of certain deciduous teeth and specific permanent teeth in an orderly sequence and predetermined pattern to guide the erupting permanent teeth into a more favorable position.

Changes to the dental morphology and jaw are major elements of hominid evolution. These changes were driven by the types and processing of food eaten. The evolution of the jaw is thought to have facilitated encephalization, speech, and the formation of the uniquely human chin.

<span class="mw-page-title-main">ASUDAS</span> References system for human tooth morphology

The ASUDAS is a reference system for collecting data on human tooth morphology and variation created by Christy G. Turner II, Christian R. Nichol, and G. Richard Scott. The ASUDAS gives detailed descriptions for common crown and root shape variants and their different degrees of expression. It also comprises a set of reference plaques illustrating dental variants as well as showing their expression levels in 3D. The ASUDAS was designed to ensure a standardized scoring procedure with minimum error in order to warrant comparability between data collected by different observers.

The analysis of dental remains is a valuable tool to archaeologists. Teeth are hard, highly mineralised and chemically stable, so therefore preserve well and are one of the most commonly found animals remains. Analysis of these remains also yields a wealth of information. It can not only be used to determine the sex and age of the individual whose mandibular or dental remains have been found, but can also shed light on their diet, pathology, and even their geographic origins through isotope analysis.

References

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