Dental Biometrics as an Aid in the Determination of Human Identity

Oommen Nainan<sup>1</sup>; Parmar V.S.<sup>2</sup>

Dental Biometrics as an Aid in the Determination of Human Identity

Oommen Nainan¹

, Parmar V.S.²

1. Graded Specialist, Orthodontics & Dentofacial Orthopedics, Naval Institute of Dental Sciences, INHS Asvini Campus, Colaba, Mumbai, India
2. Director, NIDS & Classified Specialist, Periodontics, Naval Institute of Dental Sciences, INHS Asvini Campus, Colaba, Mumbai, India

Author

Correspondence author
International Journal of Clinical Case Reports, 2015, Vol. 5, No. 32 doi: 10.5376/ijccr.2015.05.0032
Received: 17 May, 2015 Accepted: 03 Jul., 2015 Published: 29 Jul., 2015

This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Preferred citation for this article:

Oommen Nainan and Parmar V.S., 2015, Dental Biometrics as an Aid in the Determination of Human Identity, International Journal of Clinical Case Reports, 5(32) 1-7 (doi: 10.5376/ijccr.2015.05.0032)

Abstract

Dental biometrics involves the use of features unique to the human dentition as an aid to personal identification and is widely accepted within the forensic field. Teeth, with their physiologic variations, pathoses and effects of therapy, record information that remains throughout life and beyond. The teeth constitute a scientific method in forensic identification, principally due to the great resistance to the agents which provoke the destruction of the soft tissues in the corpses (putrefaction, traumatic, physical and chemical agents) and to the high morphological variability of the human teeth. Dental biometrics allow to determine several parameters of forensic interest: specimen, population affinity, sex, age, stature and individualization's factors. Comparative dental identifications play a major role in identifying the victims of violence, disaster or other mass tragedies. The comparison of antemortem and postmortem dental records to determine human identity has long been established.Based on an appropriate knowledge of the available methods, dentists can choose the most appropriate one since the validity of identity estimation crucially depends on the method used and its proper application. The dental professionals have a major role to play in keeping accurate dental records and providing all necessary information so that legal authorities may recognize malpractice, negligence, fraud or abuse, and identify unknown humans.

Keywords

Dental biometrics; Forensic; Comparison; Identification

The dawn of a new millennium has brought with it fresh challenges in every conceivable area. While the zeal to conquer new heights has created a world full of scientific advancement and technology, it has also led to a surge in crime rate, terrorism, wars, mass disasters and dreadful diseases. The 21st century has seen an increasing number of natural disasters with alarming intensity, whether it be earthquake, tsunami, heavy rainfall, cloud burst or unprecedented flash floods.

In all such disasters of large magnitude, the identity of the deceased and found human remains becomes important. Through the specialty of forensic odontology, the dental surgeon plays a small but significant role in this process (Fixot et al., 2001). By identifying the victims of crime and disaster through dental records, dentists assist those involved in crime investigation. Forensic odontology (forensic dentistry) involves the management, examination, evaluation and presentation of dental evidence in criminal or civil proceedings, all in the interest of justice. Always part of a bigger team, the dental surgeon is dedicated to the common principles of all those involved in forensic casework: the rights of the dead and those who survive them.

The field of biometrics has received much attention in the last few years because it is an interesting alternative to traditional authentication systems like passwords. As a characteristic it means a measurable anatomical, physiological and/or behavioral characteristic. As a process it means an automated method of recognizing individuals through their biometric characteristics. Under severe circumstances like that encountered in mass disasters, conventional biometric characteristics, such as fingerprints, may not be able to be used because of their low resistance. In such cases, dental features are considered the best candidates for the process of identification. The objective of forensic odontology is to identify individuals based on their dental characteristics.

Historical review

The use of features unique to the human dentition as an aid to personal identification is widely accepted within the forensic field. The use of teeth as evidence is not recent. It has been said that Nero's mistress, Sabina, in 66 A.D., satisfied herself that the head presented to her on a platter was that of Nero's wife as she was able to recognize a black anterior tooth (Luntz, 1977). Folklore also ascribes the first use of bite mark identification to King William the Conqueror, circa 1066 A.D. whose habit it was to secure his mail with sealing wax imprinted with bite. His anterior teeth were malaligned thus allowing verification of authenticity of his documents (Barker, 1982). However, forensic odontology, as a science, did not appear before 1897 when Dr. Oscar Amoedo wrote his doctoral thesis entitled “L’ Art Dentaire en Medecine Legale” describing the utility of dentistry in forensic medicine with particular emphasis on identification (Adams, 2003).

Dental Evidence and its Identification

The most common role of the dental surgeon trained in forensic odontology is the identification of deceased individuals (Jones, 1998). Dental identifications are expeditious, accurate and cost effective. Dental identifications have always played a key role in natural and man-made disaster situations and in particular the mass casualties normally associated with aviation disasters (Brannon, 1999). Persons who have been deceased for some time prior to discovery and those found in water also present unpleasant and difficult visual identifications. Dental identification takes two main forms. Firstly, the most frequently performed examination is a comparative identification that is used to establish (to a high degree of certainty) that the remains of a decedent and a person represented by antemortem dental records are the same individual. Information from the body or circumstances usually contains clues as to who has died. Secondly, in those cases where antemortem records are not available, and no clues to the possible identity exist, a postmortem dental profile is completed by the forensic dentist suggesting characteristics of the individual likely to narrow the search for the antemortem materials (Sweet, 1996).

Dental identification assumes a primary role in the identification of remains when postmortem changes, traumatic tissue injury or lack of a fingerprint record invalidate the use of visual or fingerprint methods (Neville, 2002). The identification of dental remains is of primary importance when the deceased person is skeletonized, decomposed, burned or dismembered. The principal advantage of dental evidence is that, like other hard tissues, it is often preserved after death. Even the status of a person’s teeth changes throughout life and the combination of decayed, missing and filled teeth is measurable and comparable at any fixed point in time. Dental identification also plays an important role in criminal cases, where bite marks are a vital piece of evidence and can indicate the shape of the arch, missing teeth and other teeth related peculiarities.

Principles of Dental Identification

Typically, human remains are found and reported to the police who then initiate a request for dental identification. Often a presumptive or tentative identification is available (like wallet or driving licence may be found on the body) and this will enable antemortem records to be located. In other instances, the geographical location in which the body is found or other physical characteristics and circumstantial evidence, may enable a presumptive identification to be made, frequently using data from the missing persons’ database. Antemortem records are then obtained from the concerned dental surgeon.

The fundamental principles of dental identification are those of comparison and of exclusion.Different techniques of identifying individual through dental means are available. Currently there are four types of personal identification circumstances that use teeth, jaw and orofacial characteristics, which include comparative dental identification, reconstructive post-mortem, dental profiling and DNA profiling (Sweet, 2010).

Comparative Dental Identification

Identification requires a list of the possible persons involved so that appropriate antemortem records can be located. The availability and accuracy of these records determine the success of identification. Once the postmortem record is complete, a comparison between the two records can be carried out. A methodical and systematic comparison is required, examining each tooth and surrounding structures in turn. While dental restorations figure significantly in the identification process, many other oral features are assessed and these play an increasingly important role in those individuals with minimal restorations (Table 1). Similarities and discrepancies should be noted during the comparison process. There are two types of discrepancy, those that can be explained and those that cannot. Explainable discrepancies normally relate to the time elapsed between the antemortem and postmortem records. Examples include teeth extracted or restorations placed or enlarged (Figure 1). If a discrepancy is unexplainable, for example a tooth is not present on the antemortem record but is present on the postmortem record then an exclusion must be made. Presently a computer-aided framework for matching of dental radiographs based on average pixel intensity, length to width ratio and root centre angleis used to retrieve the closest match.

Table 1 Features examined during the comparative dental identification (Pretty, 2001)

Figure 1 Comparison of Ante-mortem and Post-mortem radiographs

Regardless of the method used to identify a person, the results of the comparison of antemortem and postmortem data lead to one of four situations (Silverstein, 1995). They are

1. Positive identification: Comparable items are sufficiently distinct in the antemortem and postmortem databases; no major differences are observed.

2. Possible identification: Commonalities exist among the comparable items in the antemortem and postmortem databases, but enough information is missing from either source to prevent the establishment of a positive identification.

3. Insufficient identification evidence: Insufficient supportive evidence is available for comparison and definitive identification, but the suspected identity of the decedent cannot be ruled out. The identification is then deemed inconclusive.

4. Exclusion: Unexplainable discrepancies exist among comparable items in the antemortem and postmortem databases.

It is important to note that there is no minimum number of concordant points or features that are required for a positive identification. In many cases a single tooth can be used for identification if it contains sufficient unique features. Equally, a full-mouth series of radiographs may not reveal sufficient detail to render a positive conclusion.

Reconstructive Postmortem

The central dogma of dental identification is that postmortem dental remains can be compared with antemortem dental records, including written notes, study models and dental radiographs to confirm identity. The teeth not only represent a suitable repository for such unique and identifying features, they also survive most postmortem events that can disrupt or change other body tissues. The forensic dentist produces the postmortem record by careful charting and written descriptions of the dental structures and radiographs. If the antemortem records are available at this time, postmortem radiographs are taken to replicate the type and angle of these (Goldstein, 1998).

Dental Profiling

Dental profiles are dental charts which are completed by the odontologist. Postmortem dental profiles are employed when the tentative identity of an individual is not available and therefore antemortem records cannot be sourced. Such situations are not uncommon when remains are skeletal, grossly decomposed or are found in locations unrelated to their place of residence. The purpose of the postmortem profile is to provide information to investigators that will restrict the search to a smaller population of individuals.The information from this process will enable a more focused search for antemortem records. A postmortem dental profile will typically provide information on the deceased’s age, ancestry background, sex and socio-economic status. In some instances it is possible to provide additionalinformation regarding occupation, dietary habits, habitual behaviours and occasionally on dental or systemic diseases.

Age Determination Based on Dental Data

Age estimation is an important part of the identification process, especially when information relating to the deceased is unavailable (Willems, 2001). Human dentition follows a reliable and predictable developmental sequence which is used to determine the age. Dental radiographs may also be used to observe the morphologically distinct stages of mineralization. Such determinations are also based on the degree of formation of root and crown structures, the stage of eruption, and the intermixture of primary and adult dentitions. Conclusions are usually accurate to approximately ±1.5 years.

Ancestry and Sex Determination Based on Dental Data

Forensic anthropologists most often provide details of osteological studies, but forensic dentists can assist in the process (Steyn, 1998). The determination of sex and ancestry can be assessed from skull shape and form. Generally, from skull appearance, dentists can determine race within the three major groups: Caucasoid, Mongoloid and Negroid. Additional characteristics, such as cusps of Carabelli, shovel-shaped incisors and multi-cusped premolars, can also assist in determination of ancestry. Sex determination is usually based on cranial appearance, as no sex differences are apparent in the morphology of teeth. Microscopic examination of teeth can confirm sex of the individual by the presence or absence of Y-chromatin and also by DNA analysis. A microscopic technique can also be utilised in which the pulp tissue is examined for Barr bodies (present only in females). This technique has been shown to be of value in burnt and mummified remains and is highly accurate (Duffy, 1991).

DNA Profiling

Though not unique to DNA obtained from dental pulp, the teeth often remain the only source for DNA following incineration or other postmortem events. When conventional dental identification methods fail, this biological material can provide the necessary link to prove identity. Extraction of DNA from the human body remains a difficult task and depends upon numerous environmental factors and extraction procedures. Experience has shown that DNA from hard tissues like bone and teeth are most stable even after putrefaction of bodies (Boles, 1995). With the advent of the polymerase chain reaction (PCR) technique that allows amplification of DNA at pre-selected, specific sites, this source of evidence is becoming increasingly popular with investigators. Comparison of DNA preserved in and extracted from the teeth of an unidentified individual can be made to a known antemortem sample (stored blood, hairbrush, clothing, cervical smear, biopsy, etc) or to a parent or sibling by a PCR-based method. PCR analysis of DNA, sourced from the dental pulp and the subsequent analysis of the amelogenin gene can also be used for sex determination.

Radiographic Examination

Comparison of antemortem and postmortem radiographs is the most accurate and reliable method of identifying remains. Observations such as distinctive shapes of restoration, root canal treatment, buried root tips, bases under restorations, tooth and root morphology and sinus and jawbone patterns can be identified only by examination of radiographs. In some instances a single tooth may be all that remains, and upon comparison of radiographs, a positive identification can be made. Original antemortem dental radiographs are of immense value for comparison; therefore it is essential that all routine radiographs exposed during the course of dental treatment be documented and preserved suitably.

Other Methods of Dental Identification

In some instances more novel and innovative techniques have been applied. Dentures have been recovered from patients and then fitted to casts retained by the treating dentist or laboratory, and this has been an accepted method of identification (Jacob, 1987). In this regard, patient name inscription or labeling of acrylic dentures using a metallic inclusion denture marker is often a useful step before denture insertion and offers a vital clue in identification. Other dental appliances, such as removable orthodontic appliances have also been used for identification purposes. A few authors have also described the use of palatal rugae patterns rendered on dental casts to compare with found remains. Positive identifications have resulted from this technique.

Mass Disaster Identification

The identification of large numbers of casualties in mass disasters are complex and fraught with hazards, both physically and emotionally. Natural disasters and transport accidents form the majority of cases in which dental identifications are needed, in which both fire and trauma are often severe. Fires and collapse of heavily occupied buildings are another source of multiple problems of identification. The forensic odontologist can be an important member of the investigating team, the composition of which varies, depending on the nature of the disaster. Generally, the team includes a coordinator or head of the team, a pathologist and various specialists with experience related to the particular type of disaster, in addition to the forensic odontologist.Disaster victim identification (DVI) teams are required to process the entire task in four main steps i.e, body tagging and bagging, finger printing, forensic pathology and forensic dentistry.

In addition to analysis of teeth, the most common methods of identification include visual identification, fingerprinting, serologic and DNA comparison, and anthropologic examination of bone. Each method has its advantages and disadvantages. Since teeth are heavily calcified, they can resist fire as well as a great majority of traumas. Dental examination is significantly confounded when heat and flames have fragmented tooth enamel, and sootand smoke have been deposited on the teeth. Generally, teeth and restorations are resistant to heat, unless they are exposed directly to flame (Pötsch, 1992).

Role of the Dental Surgeon

An annual dental check-up offers a great opportunity for the dental surgeon to meticulously note down and chart the dental status of the individual with a yearly update.The dental record is a legal document prepared by the dentist, and contains subjective and objective information about the individual.It is suggested thatthe results of the physical examination of the dentition and supporting oral and surrounding structures should be comprehensively noted down in written form or on a computer database. In addition, the results of clinical tests, study casts, photographs and radiographs become components of the record, and should be preserved with the dental surgeon for 7 to 10 years. Any changes in the record should not be erased, but corrected with a single line drawn through the incorrect material. This method permits the original entry to remain readable and removes any questions about fraudulent intent to alter recorded information.

Computer-generated dental records are rapidly becoming more common for dental records. Automated dental identification system is a computer aided software for the postmortem identification of deceased individuals based on dental characteristics, specifically radiographs. The obvious advantage of the electronic record is that it can be easily networked and transferred for routine professional consultation or forensic cases requiring dental records for identification. Patient specific dental records may be stored on a digital smart card, handed over to the individual at the initial visit to the dental clinic and updated on a yearly basis. Whether dental records are preserved in written form or on a computer database, following the principles of record management ensures that all dental information that may be required to resolve a forensic problem is properly maintained and retrievable.

Advances in Forensic Odontology

New advances in forensic science allow digital comparison of teeth and bitemarks at a 3-dimensional level. This includes the following:

1) Automatic dental code matching: The dental records &/or bite marks are run through the computer to find the closest match

2) OdontoSearch: This software compares the data base of missing people obtained from various agencies, for their dental characteristics

3) Automatic dental identification system: Here the database allots a dental code number for similar features in the dentition. This system produces a list of people who have the same dental code number to narrow down the search.

4) Lenticular card & Micro Secure Digital (MicroSD) card: Here the patient's information is stored in the denture in the form of a photograph, video and text. The Micro SD card is laminated and placed either on the lingual flange of the mandibular or buccal flange of maxillary denture. The MicroSD holds large amounts of information that can be easily modified (Colvenkar, 2014).

5) 3D analysis: 3D scans of dental casts are used to generate overlays of the dentition which is then compared with the obtained remains.

Conclusion

Forensic dentistry plays a major role in the identification of those individuals who cannot be identified visually or by other means. The unique nature of dental anatomy and the placement of custom restorations ensure accuracy when the techniques are correctly employed.Each dental surgeon has a responsibility to understand the forensic implications associated with dental practice. Appreciation of the forensic field should give the dental clinician another reason to maintain legible and legally acceptable records and assist legal authorities in the identification of victims of disasters.

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