Dental Imprints – A Review

Introduction

Teeth being the hardest tissue in the body and have the ability to withstand high levels of thermal, chemical and physical insults. Therefore teeth and the dentition as a whole, is considered as an important source of identification in the living and the dead. Dental identification techniques are quite accurate and economic and which varies from simple viewing of the involved area, to photography, to the more microscopic DNA levels. Vital source of information can be obtained from teeth when the soft tissue of the body are decomposed andhard tissue like bone cannot be used for identification.⁽³⁾

According to Professor Keith Simpson, professor of forensic medicine, “Dental data provide detail of a kind, that was previously thought to be provided only by fingerprints; A reason for coming to regard teeth as of very great importance in the identification of an individual.⁽²⁰⁾

Forensic odontology deals with age estimation, sex determination, bite mark analysis and post-mortem, ante mortem, reconciliation and debrief, Disaster victim identification (DVI)⁽²⁵⁾

History

Dr. Joseph Warren, was recorded the first medico-legal identification of a body using dental means of a person who was killed during a battle during American revolution in 1775, by musket ball, through the skull, who was buried in a mass grave and after 10 months was exhumed and identified by the dental work of Paul Revere and given a hero's re-burial in 1776.⁽²⁾

Paris was pioneer in mass forensic identification in the Bazaar de la Charité tragedy occurred on May, 1897. Where 126 people were killed and relatives tried to identify the badly charred bodies. 30 bodies were eventually identified because of meticulous dental record keeping of amalgam fillings, gold repairs, crowns and evidence of extraction spaces noted in the mandibles and maxillae of the victims.⁽²⁾

Dr Oscar Amoedo'swork ''L'Artdentaire en médicinelégale”, which contained the works on identification procedures used in Paris disaster which formed a framework to be used as basis in future.⁽²⁾

Definition

Forensic odontology is an interdisciplinary field between forensic medicine and dentistry. It is that branch of dentistry which is concerned with the practice of the law and the administration of justice.⁽²²⁾

Age estimation

Apart from ones basic right and also having it documented gives an individual's identity. Date of birth is required to enter school, work, get married and get a pension. It is also required in events related to justice and dealing with offenders rightfully according to their age.⁽¹²⁾

Chronological age can be estimated by determining physiological age, which is the age at which a developing system or organ reaches a specific stage. A set of criteria exist for a system or organ to be an ideal age indicator. It has to develop over a long period of time, be stable and not be affected by environmental or racial factors and have recognisable and measurable stages that can be assessed in the living as well as the dead. The human dentition develops over nearly a third of the average human life, with easily detected and predictable stages. Dental hard tissues are very stable and minimally affected by environmental factors, socioeconomic status, nutrition, dietary habits and even by endocrine factors. These qualities make the developing dentition the best age indicator compared with other systems.⁽¹²⁾

Bite marks

Mac Donald (1974) defined bite mark as 'a mark caused by the teeth either alone or in combination with other mouth parts'.⁽⁹⁾

Bite marks occur in a variety of crimes such as assault, rape, and murder and child abuse. Crucial anatomical details obtained from the human bite mark, includes dental arches, teeth, interproximal embrasures, tongue, lips, gingiva and palatal rugae. In female victims, bite marks are most common on the breasts, arms and legs; in male victims, arms and shoulders are the most common sites.Bite mark identification is based on the individuality of a dentition, which is used to match a bite mark to a suspected perpetrator. Matching is by toothby- tooth and arch-to-arch comparison using parameters of size, shape and alignment.⁽¹⁾

DNA

Forensic odontology investigators are now more familiar with advanced molecular biology technologies as they need to perform identification in fires, explosions, decomposing bodies and skeletonized bodies.⁽¹⁶⁾ Today swabs of the bite marks for DNA can be matched either from a suspect at the time or by a later speculative search.⁽²⁾

The tooth is the most important source to extract DNA. It is a preserved package of DNA protecting it from adverse environmental conditions.⁽¹⁶⁾ DNA profiling systems can expose the exact identity of a person. DNA extracted from the teeth, dentin and pulp are rich sources of DNA. Sectioning the tooth provides greater access to pulp. Once the tooth is opened, walls of the pulp chamber can be curetted or instrumented with a slow rotary burr. Then pulp tissue can be collected in a wide open sterile tube. In case of dried specimens, the pulp may be mummified parchment-like. After instrumentation, the chamber is best irrigated with buffer. Ultrafiltration of the liquid at the lab will remove the cellular material needed for analysis. (Smith et al. 1993).

Tooth is the rich source of DNA which can be obtained from the pulp via ultra-filtration of the liquid which can isolate cellular material needed for analysis.

DNA can be extracted from the crown body, root tip, and root body. The root body yields the highest quantities of DNA (Gaytmenn and Sweet 2003).

Mass disaster

Mass disaster may be due to natural causes such as meteorological or geological events or man-made causes (structural failures, transportation failures, crowd surges, fire, explosions, war and terrorism). Disasters may be open or closed, or both. Open disaster being where there is no immediate tentative identification of the deceased, and there is delay in obtaining ante-mortem data. A closed one is where there is a readily available list of possible victims (e.g. a plane crash where there is a passenger list), and ante-mortem comparative data is quickly available. Disaster gets complicated when it's combined for example, a plane crash into a residential area.⁽¹⁵⁾

Identification will rely on comparison between postmortem dental examination and antemortem dental records. When records are not initially available, then characteristics of the oro-dental structures may be used to indicate age, sex, medical, dental history, etc.⁽³⁾

Antemortemdental records focus on all recorded information of the diseased hand written and/or digital clinical information, dental and/or facial radiographs, clinical photographs and dental models, smiling photographs, and also specific information from relatives and friends. Antemortem smiling photographs are very helpful in comparing post-mortem dental findings, such as discoloration, missing, and malformed or misaligned anterior teeth.⁽³⁾

Dental Reconciliation

The process undertaken by the odontologist of comparing the information obtained in post-mortem clinical dental examination with that contained in the antemortem dental records.

Facial mapping techniques can be utilized when dental records are not available, they include facial anatomical points and teeth, utilizing anthropometric measurements and relative proportions or photographic superimposition of an antemortem smiling photograph with an equivalently positioned post-mortem facial photograph.⁽³⁾

Some dental restorations undergo change when exposed to heat. High temperatures cause silver-amalgam fillings to evaporate mercury which could amalgamate superficially with neighbouring gold fillings. Gold shows through the surface upon scratching, and also identified by observing the outline and form of the filling.⁽¹⁹⁾

Conclusion

Forensic odontology is much of science than art which requires or demands patience and time to study, research and to plan. Dental identification technique is quite reliable and economic. Hence more research and study by the dental personal is required.