To begin with, forensic odontology is a sub-specialty of dentistry or dental science. It connects or creates a bridge between law and dentistry. This is a very important aspect when it comes to mass disasters as a result of a fire break-out, earthquakes, or any calamity for that matter. Apart from mass destructions this specialty also plays an important role in solving major crimes.
In addition, it mainly focuses on identifying a person. Mainly, people who cannot otherwise be identified by visual means.
HISTORY OF FORENSIC ODONTOLOGY:
‘Forensic odontology’ is a very wide term. It encompasses a lot of aspects. The term ‘forensic’ means legal. And, ‘Odontology’ means relating to the tooth or dentistry on the whole. It dates back to Roman times where this practice of using the tooth or related structures to identify a crime victim started and developed.
Forensic odontology was first given by Keiser- Neilson in 1970. The forensic odontologist assists legal authorities. They examine dental evidence in various situations.
SCIENCE BEHIND FORENSIC ODONTOLOGY:
To begin with, teeth are the most durable organs in the human body. They can remain intact like bones even after the whole body burns away. Teeth have helped humankind to understand our past. Moreover, details about our ancestors.
It is a lesser-known fact. But every dentist has some responsibilities in this field. It is the responsibility of a dentist to report abuse in any form. It includes elder or child abuse, intimate partner violence (IPV) – a form of sexual abuse.
The antemortem and postmortem records are used for comparing and identification. These kinds of data are useful when identifying an individual or a group of individuals in cases of mass fatality incident (MFI) cases.
USES OF FORENSIC ODONTOLOGY:
- Importantly, for assessing the age of the patient
- Easy to perform gender identification.
- Dental identification in cases of victim identification, physical and child abuse, malpractice, bite mark identification, fraud, and personal identification cases
- Presentation of dental evidence as an expert witness.
- Collection and analysis of patterned marks (bite marks) from inanimate objects. Comparison of the injured tissues and dentitions (human and animal).
- In addition, the management and maintenance of dental records that comply with legal requirements to document all unique dental information. These data are the foundation of the dental identification of the patient.
What are dental records and how are they useful?
Dental records are legal documents. The dentist or dental practice owns the records. It contains all subjective and objective information about a patient. Laws regulate and protect information. These records are very useful in matching and identifying the victim.
For example: In some countries, dentures of edentulous people have a social security number. This is in an area of the denture that will not interfere with the aesthetics of the denture. Victim identification is possible by comparing denture identification numbers with the antemortem records.
SEROLOGICAL AND GENETIC COMPARISON IN FORENSIC ODONTOLOGY:
Firstly, it is an established fact that every individual is unique by virtue of his or her chromosomal DNA.
It’s an ‘ultimate identification material’. It was first used forensically to obtain a conviction in a criminal case in the year 1986. Since then, DNA comparison has become an accepted forensic method to resolve problems of identification.
Above all, even dried-up blood samples and fluids can be analyzed for markers, with appropriate laboratory tests.
DNA of the human cells has a mitochondrial (mt-DNA) and chromosomal DNA.
- Chromosomal DNA- 2 copies of this DNA is incorporated are incorporated into the nuclei of a person’s cells by DNA provided from both the parents.
- mt- DNA- Hundreds of copies of mt- DNA are contained in the cytoplasm of the cells. It is maternally transferred and can be isolated from cells without nuclei, such as RBCs. It is single-stranded and circular.
Meanwhile, as there is no mixing of DNA, it can be compared with that of distant maternal relatives to effect identification when other reference sources are unavailable.
Firstly, there are 2 prime laboratory techniques used to compare and evaluate the fragments of DNA material from a suspect or victim’s biological forensic specimen. (Eg. Teeth, soft tissues, saliva, semen, vaginal fluid).
- RFLP- Restriction fragment length polymorphism.
- PCR- Polymerase chain reaction
Both are extremely accurate, precise and reproducible. In addition, these are used when the conditions of the sample DNA presented dictate the need for their respective advantages.
Regardless of the method used in the processing of the DNA, harvesting the evidence remains the same.
- Sterile cotton wetted with distilled water is rolled in a circular motion over the surface of the skin or object with moderate pressure.
- Air drying of the swab.
- A second dry cotton swab is rolled over the same surface of the skin or object using moderate pressure and circular motion to absorb all moisture left by the initial swab.
- Air drying of the swab again.
- Properly labeled storage containers store the swabs. Kept in labs for frozen storage at -20 o C (-4o F).
Control samples include,
- Whole blood,
- Autopsy tissue samples or
- Oral buccal swabs from a living sample.
Moving on to the two methods of collection of sample collection the RFLP and PCR.
RFLP method(Restriction fragment length polymorphism):
Firstly, it involves splitting source DNA into thousands of fragments using “biological scissors” known as restriction enzymes. The fragment size varies among individuals related to a number of base pairs. (variable number of tandem pairs- VNTR).
- The short segments of DNA contain a number of repeat units that differ among individuals.
- Gel separation separates the fragments. A nylon mesh helps in transfer.
- Identification of specific DNA fragments.
- Analysis of a series of different VNTR loci permits the generation of an individual DNA profile.
A match of four or more VNTR loci is consistent with a positive match between DNA evidence gathered from suspect, victim, or crime scene evidence.
DISADVANTAGE OF THE RFLP METHOD:
- Firstly, this method requires large amounts of high molecular weight DNA.
- Small DNA samples (< 100 nanograms) or degraded evidence in which the DNA has become denatured. Due to extreme heat or pH variation, it requires an analytical method other than RFLP.
PCR (POLYMERASE CHAIN REACTION):
Meanwhile, to overcome the disadvantages of the RFLP method, PCR can be used.
With PCR, minute quantities of DNA or DNA that have undergone degradation can be accomplished with the highly sensitive PCR test.
Similarly, using this technique, smaller VNTR loci of a specific DNA sequence can be amplified into enough copies for sufficient analysis. Because of the high degree of sensitivity, PCR analysis is being used to evaluate small amounts of DNA. AmpFLP (amplified fragment length polymorphism) analysis refers to DNA analysis of microsatellite loci and minisatellite loci (the position of a gene or mutation in a chromosome) using PCR.
AREAS OF THE MAXILLOFACIAL REGION USED TO OBTAIN DNA MATERIAL:
- The hard and soft tissues of the oral cavity and saliva are often good sources of DNA material.
- A tooth or a jaw fragment capriciously destroyed can result in the loss of valuable radiographic or anatomic sources for eventual dental identification.
- Besides, the obvious source of DNA from human tissues, the forensic dentist often considers the evaluation of chewing gums, cigarette remains, licked envelop, stamps, or other similar inanimate objects as potential sources for DNA evidence using PCR analysis.
This is one of the earliest methods of scientific identification of criminals. A French officer ‘Alphonse Bertillon’ developed this system in the later part of the 19th century. More consistent analysis of epidermal frictional ridges later replaced this method.
Likewise, it is a known fact that the ridge-like patterns on the fingertip and palm are unique for each pattern. Genetics determines friction ridges. Secondly, not even homozygous twins have the same pattern.
There are 3 predominant patterns, namely,
In addition, the morphometric variation in the combination of the loops, arches, and whorls permits the scientific comparison of fingerprint records with the friction ridges of the unidentified decedent.
ADVANTAGE AND DISADVANTAGE OF ANTHROPOMETRY:
Fingerprints has static characteristics that remain unchanged throughout one’s life.
Meanwhile, the teeth and the supporting structures have fluid characteristics. Dental patterns change as teeth erupt, exfoliate, decay, become restored. Further, prosthetic devices replace the extracted space.
Above all, some private dental clinics maintain dental records. Governmental agencies maintain the fingerprints. For example, the CJIS division of the FBI contains the largest biometric database in the world. It approximately contains 130 million fingerprint records (Criminal, civil, known, and suspected terrorist formats).
To sum up, with modern-day improvements in laboratories and technology, this field is growing and coming up with very new and innovative methods of victim identification.