Forensic Odontology

Issues of Concern

Responsibilities of forensic odontologist include[3]:

• Identification of human remains
• Age estimation
• Identification following mass fatalities
• Assessing bite mark injuries
• Assessment abuse cases (child, spousal, elder)
• Civil cases involving malpractice

Clinical Significance

Identification of Human Remains

Every human on earth has an identity in life; empathetic societies require that this identity is acknowledged even after death. Once a person departs from this world, there may be many concerns, such as monetary dealings and family relationships, which require attention. Humanitarian causes for human identification include[4]:

• Need for authorities to return the appropriate body to the next of the family
• The need for people to know with certainty the fate of a family member
• The need for people to understand the circumstances surrounding the death of a member of the family and mark with a suitable ceremony at the end of a person's life

Forensic odontology demonstrates a central role by presenting the pieces of evidence from the oral and maxillofacial region (including the teeth), which will be used in a jurisdictional setting and acknowledged by the court of law and the general scientific community to affirmatively and rightly separate truth from untruth. Forensic identifications in general, by their nature, are multifaceted team exertions that characteristically embroil the mutual coordination of law execution bureaucrats, forensic sciences experts such as forensic odontologists, anthropologists, pathologists, serologists, criminalists and other consultants as deemed essential.

Dental identification of human being ensues at different causes and circumstances. The victims of death in violent crimes, motor vehicle accidents, workplace accidents, fires, etc. can be mutilated to a great extent, so that family member identification is not reliable or desirable.

Individuals who have long since deceased before detection and those found immersed in water are also visually challenging to identify. Proof of identity through dental structures has long been of key importance in natural and man-made disasters and in particular, mass fatalities usually related to aviation catastrophes. Dental identification remains vitally important because of the lack of an extensive database for fingerprints.[5]

Age Determination Based on Dental Data

Age assessment is a sub-discipline of the forensic sciences and is a necessary measure of the identification practice, principally when evidence concerning to the deceased is unreachable. A small variation in tooth development and eruption among individuals has made the dental estimation of chronological age, a crucial technique of age determination. Human dentition follows an unswerving and anticipated developmental sequence, beginning about four months after conception and continue until the mid-third decade of life when the development of all the permanent dentition is complete.[6]

Age determination is also formulated based on the degree of formation of crown and root structures, the stage of eruption, and the intermixture of primary and adult dentitions. It also helps in identification if an individual is having a comprehensive dental record and presence of any uniqueness like decay, malposition, overlapping, rotations, and restorations/fillings with different materials, diastema/gaps and dentures/Implants, etc.

Teeth are well known as the strongest structure of the entire human body and are thus extremely durable and identically resistant to external impacts like putrefaction, fire, explosions, and chemicals, etc., which brand them accessible for a broad post-mortem duration. Age can be assessed from the teeth by several techniques like the eruption of teeth, which is acknowledged as a good indicator of the age of the person. Other changes, which are noticeable with increasing age, are attrition, periodontal disease, secondary dentine formation, and root translucency, resorption of roots, root roughness, apposition of cementum, color change in the crown and the roots.

By analysis, the tooth development in a child and consequently comparing with developmental tables/charts can give an age estimation in the pediatric group, (including fetuses and neonates). Conclusions are generally accurate to around plus or minus 1.5 years. Graphic charts like those established by Ubelaker elucidate the dentition growth from five months in-utero to 35 years after birth, exemplifying all the stages of dentitions. Some odontologists promote the application of aspartic acid racemization and claim plus or minus four years of accuracy.[7]

In the year, 1947 a technique was developed based on structural tooth changes by Gustafson.[8] According to his technique, there are six criteria. Those include attrition, amount of recession in gingiva, secondary dentin formation, apposition of cementum, resorption, and transparency of root. These alterations were itemized with a predetermined score ranging from zero (0) to three (3), and an equation put together for linear regression aimed at calculating the age of an individual. The relationship constant achieved was 0.98. This technique is considered as the standard for human age estimation and is being used ever since its development. The core shortcoming of Gustafson method was the setting of equality for all the standards for equivalency.

Kashyap revised the Gustafson system using objective dimensions, removing the measures like the recession of gingiva and resorption of the root. He defined the age of a person by gauging the secondary dentin by its length which is the development of the pulp chamber and further accessing the root for the thickness of cementum formed.[9]

Additionally, advanced methods were developed, which include the practice of using scanning electron microscopes and energy dispersive X-ray analysis (SEM-EDXA), an advanced technique to scan dentin for age estimation. Contemporary research from the United Kingdom observed the root length usage in estimating the age of a pediatric individual. Another method developed is known as the Average stage of attrition (ASA) method which is a clinical way of measuring the attrition of molar cusps; it measures the attrition of respective molar cusps and subsequently uses them in average calculations.[10]

Socio-Economic Status

Dental restorations may indicate the economic, regional, and racial background of an individual. Restoration methods used in some countries or regions may be rare or not used in other areas. A costly restoration can indicate a person's economic status. The wear and stain patterns can suggest work or personal habits like smoking.[11]

Sex/gender Identification

Many a times identification of sex/gender using skeletal remains, presents a problem for forensic professionals, particularly when merely fragments of the body are recovered in the cases of ethnic studies, biochemical and nuclear-powered bomb blasts, mishaps, and natural catastrophe investigations. Forensic odontologist can contribute to the field through the help of other experts to conclude the gender of the remains using teeth and skull characteristics. Different topographies of teeth like crown size, shape and root length, etc. are physiognomies for different genders. There are also differences in skull patterns and qualities in different genders. These are of added advantages for forensic odontologists in identifying the genders of the deceased bodies. The presence or non - compliance of Y - chromatin and deoxyribose nucleic acid (DNA) analysis can confirm sexual identity by microscopic examination of teeth.[12]

Race Identification

There have been attempts to determine to what extent the tooth crown morphology can be used to determine expectable forms of biological relationships among humans. Initially, anthropologists and odontologists in France and Germany showed that certain morphological variants, like the number of cuspids of molars, differed between the main human races. Our global population is traditionally riven into three different categories, Caucasus, Mongolian and Negroid, by physical anthropologists.[13]

Caucasoid: The Caucasoid dental complex includes:

• The absenteeism of shovel-shaped incisors
• High incidence of bilateral counter winging or straight axial orientation of the central incisors
• The absence of premolar occlusal tubercles (enamel pearls)
• High incidence of the cusp of Carabelli
• The absence of expressions of the protostylid of the sixth cusp and the seventh cusp

Mongoloid: Mongoloid dental complex includes:

• High incidence of shovel-shaped incisors
• Enamel pearls occur more commonly on the premolars
• Cusp of Carabelli or tubercle commonly presents in the negative form with pits and grooves

Facial Reconstruction and Facial Superimposition

If the post-mortem data does not produce the distinctiveness of the dead person, it will be obligatory to recreate the person's external appearance during life, especially the facial profile; this is the forensic artist's obligation to use the dental profile to reconstruct the face. The use of ante-mortem pictures/photos to document facial superimposition of skeletal and dental fractures have been useful in identifying missing individuals. This procedure necessitates the readiness of appropriate ante-mortem pictures/photos displaying the teeth. Frequently, angulations and magnification enforce hitches in positioning and arranging the images.[14]

Other Methods of Dental Identification

The above two processes, comparative identifying and postmortem profiling, are the most common dental identifying methods. Additional new and innovative techniques are, however, necessary in some instances. Most frequently, the dental prosthesis has a label with the patient’s name or unique identification numbers or even the latest bar-coding and QR coding systems.

Also, unlabeled dentures recovered from patients can be fit to casts made and retained by the treating dentist or laboratory, which helps in the comparison. For identification purposes, other dental devices, like removable orthodontic braces are also useful. 

Rugoscopy/Palatoscopy

In forensic odontological identifications, the stomatognathic system plays a very significant role due to the immutable anatomy of the teeth, jaws and associated soft tissues. In certain conditions, if teeth are missing due to any reason, then the habit of using the palatine rugae has been advocated as an alternate technique for identification. Palatoscopy or palatal rugoscopy is the name given to define an identity of the person through the study of palatal rugae. Palatal rugae start developing in the 3 months of intra-uterine life from the calcified mesenchymal tissue wrapping the bone. The exact arrangement, configuration, and orientation takes place by approximately 12 to 14 weeks of prenatal life and remains robust until the oral-mucosal structures regress after the demise of the person. The palatal rugae display distinctive features that can be used in conditions when it is challenging to recognize a deceased person through fingerprints and dental hard tissue records.[15]

Rugae are protected against trauma by their inner position in the head and by the tongue and buccal pad of fat from heat. Research shows that no two individual’s palates are identical in their formation, arrangement, and alignment and that the palate-print does not alter during growth; it remains unwavering and in one position throughout life. Hence, this method is regarded as an alternative means for human identification.

Lip prints (Cheiloscopy)

The wrinkles and grooves in the labial mucous membrane (sulci labiorum) form a distinctive pattern, known as "lip prints," and this study is known as cheiloscopy. There are many elevations and depressions on the external lip surface. These are unique to individuals like fingerprints. A lip print demonstrates a surface with visible elements of furrow lines. This feature helps to identify an individual's gender.[12]

DNA in Forensic Odontology

The dental tissues are an excellent source of DNA because of their resistance against environmental attacks such as incineration, immersion, trauma, and decomposition. This biological material may provide the necessary link to demonstrate identity when conventional methods of dental identification fail. This evidence source is becoming increasingly popular among researchers with the advance of the polymerase chain reaction (PCR), a technique that enables DNA amplification at a preselected location. The antemortem specimen from any DNA source, including toothbrush and hairbrush or blood samples, biopsy, clothing or another individual item that has belonged to the deceived, is here matched with the DNA extracted from a human remains at disaster sites.[16]

If the genomic DNA is not concentrated enough for conclusive identification, then mitochondrial DNA (mtDNA) exists in a high number of copies in every cell and is very useful. The study of mtDNA is a powerful tool in forensic cases if the maternal form of mtDNA that matches with parents and siblings of the deceased and there is no antemortem comparison sampling.

Dentinal fluids contain species-specific antisera information, which is capable of assisting in identifying and differentiating the remains of human beings from non-humans for as long as 12 months after the death of the victim. When the only cellular residue is recouped from bone or teeth fragments, it may be possible to establish the gender of an individual by the presence or absence of BARR bodies or sex chromosomes.[17]

Bite Mark

The pattern in a bite mark is unique, like fingerprints, radiographs, and DNA. Teeth are often used as a weapon in mortal combat circumstances such as life and death struggles between attackers and victim. The teeth may be the only defensive method available for a victim to inflict serious harm on an attacker. The pattern of bite-mark can be present, depending on the circumstances, in foodstuffs, other objects, or on an attack or homicide victim itself. It is also well known that sexual assailants, including sexual assassination, rape, and child sex abuse, often bite their victims to express domination, fury, and animalized conduct. The teeth are an essential part of our natural arsenal. When violent abuse involves the use of teeth as a weapon, the morphological and anatomical features of bite marks may be useful to identify the victim. Comparisons of bite-marks include dental arch size and shape, tooth positions and individual dental characteristics. The sizes, shapes, and patterns in the upper and lower dental arches and the biting edges of the anterior teeth are considered unique to that individual. The main reason for this is the sequence of anterior and posterior teeth eruptions. The resulting dental configuration creates a pattern that is identifiable compared to similar patterns in bitten objects, which determines the likelihood of a particular person leaving their "calling card." These include human skin, clothing, envelopes, gum, telephone receivers, and food. Human bite-marks are most common in the victim's skin and may be present nearly every part of the human body. In sexual attacks, women are bitten in their breasts and legs, whereas bites on their arms and shoulders are most common in males. Arms and hands often receive bites when the arms are held up to prevent an assaulter from attacking as a defensive mechanism.[18]

Teeth injuries can range from bruises to scrapes and cuts or lacerations. It is certainly possible to produce enough force to allow the biting edges of the teeth to penetrate the deep skin layers. When a lot of time from injury to discovery elapses, the diffuse nature of the contusions and changes associated with injuries may further reduce the evidence; this is especially true in the case of living bite victims but also for the deceased.[19]

Non-human bite injuries can sometimes present on victims. The differences in aligning and the specific morphology of the teeth commonly distinguish animal bites from human bite lesions. Animal bites often lead to skin laceration, shear injuries and open wounds, instead of impact injuries. Dog bites characteristically demonstrate a narrow anterior dental arch and consist of deep tooth wounds over a small area, and perhaps it is the most common nonhuman bite. During violent biting, a dog (or other carnivorous mammals) is more likely than a human to cause human tissue avulsion. Cat bites are small and round with sharp cuspid-tooth impressions resulting from the teeth’s conical shape.

Documentation of Bite Mark Evidence

As the physical and biological evidence from the bite mark soon deteriorates, photographs provide the most reliable information, preservation, and require careful documentation. Photographs may be in black and white or color, with dimensions included in the pictures/photos. Other methods of documentation include the collection of saliva washings and suitable impressions.[20]

More than 80% of the global population secrete certain specific ABO antigens in their saliva.  The cellular contents of saliva have proven to be an appropriate source of genomic DNA, which can be an excellent aid to identify suspected abusers.  The double swab technology is used as a protocol for the collection of saliva samples. First, the surface contacts of the tongue and lips are washed using light pressures and circular movements by a cotton swab moistened with distilled water. Then, the remaining moisture left on the skin by the first swab is collected with a second dry swab. At room temperature, both swabs are thoroughly air-dried for at least 45 minutes before release for testing by legal authorities.

An additional technique for capturing bite mark evidence is the exact impression of the bitten surface to record any teething irregularities, such as cuts, abrasions, etc. Polyether impression material, vinyl polysiloxane, is commonly used to record impressions. The impression material can be rigidly supported with dental acrylic or plaster; this permits accurate recording of the skin's curvature.

Forensic odontologists also use advanced techniques to improve photographic evidence. These advanced techniques include electron microscopy scanning (SEM), videotape analysis, and enhancement of computerized images.[21]

Identification in Mass Disasters

Dental identification has always been of key importance in natural and man-made disasters and, in particular, in aviation-related mass disasters. In a mass disaster situation, the identification process is the same as in routine dental identification of a deceased, but the conditions under which the process is carried out are much more complicated. The impact of mass fatality is a significant challenge for local governments. The infrastructural damage including hospitals, transport, and communications hampers recovery is another great burdened challenge.[22]

Flaws in the standardization of dental records (which means there will be a great variety of details in antemortem and postmortem documents), poor working conditions, psychological stress, decomposition, the maiming of human remains at a disaster site, all complicate the identification processes. Disaster preparedness is the basic requirement for the correct management of these situations. In those situations, a hierarchy of an antemortem, postmortem and reconciliation teams must be established to identify the deceased victims. Team leaders must coordinate the work with liaison officials. The results are communicated to the identification board headed by a commander; the operation requires teamwork involving experts from different specialties. Only if well trained key experts with the selection of the appropriate forensic diagnostic devices can disaster victim identification be successful. The forensic odontologist has an active role in all phases of an identification process as a key member of the identification team. More destruction, fragmentation, and mangling of human bodies than ever before may be part of catastrophe scenarios, making it much more difficult to identify victims.[23]

The forensic odontologist is helped by knowledge of the site and equipment to perform procedures quickly. Pre-planning of the facilities is obligatory. The field of operations and the magnitude of the catastrophic effect drives the size and structure of the forensic dental team. Training and practice in different areas of forensic dental medicine at various levels - administrative, technical, coordinating, etc. results in a polished group that has a high potential to achieve successful results on an as need basis. These new challenges are met by forensic dentists who use modern scientific methods to identify them. The key to successful disaster management is the planning, organization, coordination and disaster response exercises.  Forensic dentists have helped resolve many large-scale disasters. The tsunami in 2004 in the Indian Ocean is probably the most prominent example of forensic dentists identifying numerous victims. In Thailand, almost half of the victims were identified by dental methods alone.[22]

The organization of the identification center divides into subsections, which include forensic dentistry as a sub-section. The section on forensic dentistry is further broken down into three sections and is led by a team leader responsible for the operations of the identification center. The role of the forensic dentistry chief is the responsibility of the whole section to manage, facilitate, coordinate and spokesperson. Each forensic dentistry subsection should have a person designated to be responsible for that subsection's activities.

Domestic Violence and Child Abuse

The World Health Organization (WHO) has declared that violence is a significant and growing problem of public health around the world. The main aim of this landmark declaration was for health workers to detect and manage cases of violence, including abuse of vulnerable populations, i.e., children, the elderly, and women. Four different forms of violence are also identified by the WHO: physical, sexual, psychological and neglect. In the orofacial region, all sorts of violence and abuse can manifest, and therefore dentists should be concerned about this manifestation. These manifestations include fracture of anterior teeth, fractured alveolar bone, lacerations of the labial and buccal mucosa, lacerations to the frenum and bruises to the lips, face, and neck. Consequently, injuries to the oro-facial region should give the treating dentist reasonable suspicion. The suspicion should lead to investigation and reporting, but reporting should be well-considered.[24]

Enhancing Healthcare Team Outcomes

In identifying victims, the forensic odontologist plays a crucial role. General dentists should be aware of the use of dental forensics. The unique characteristics of the teeth allow the forensic dentist to compare anti-mortem and post-mortem dental registers and to conclude on the identification of the victim. Other important advances for the legal authorities during the identification process might be the dental records which are used to offer patients the optimal dental service. All dental therapies should, therefore, be properly registered and maintained. Dental doctors are at the forefront of detecting signs of abuse in their patients, as are other healthcare workers. Bite marks are useful to identify the abuse of children and offenders of various violence; however, caution is necessary when using only bite mark proof. The criteria for abusive injury and reporting mechanisms should be understood to ensure that the concerned authorities respond correctly. Forensic nurses, dentists, pathologists, and forensic pathologists should all be educated in this area of medicine and work together for the preservation of evidence anti-mortem. [Level V]