Introduction
Forensic means legal: A word that comes from Latin, meaning “to the forum”. The forum was the basis of Roman law and was a place of public discussion and debate pertinent to the law. Keiser-Neilson in 1970 defined Forensic odontology (FO), or forensic dentistry, as “that branch of forensic medicine which in the interest of justice, deals with the proper handling and examination of dental evidence and also with proper evaluation and presentation of the dental findings”.1 Forensic science refers to areas of endeavor that can be used in a judicial setting and accepted by the court and the general scientific committee to separate truth from untruth.2
Forensic odontology has three major areas of utilization:
Diagnostic and therapeutic examination and evaluation of injuries to jaws, teeth, and oral soft tissues,
The identification of individuals, especially casualties in criminal investigations and/or mass disasters,
Identification, examination, and evaluation of bite marks which occur with some frequency in sexual assaults, child abuse cases, and in personal defense situations.3
The common methods used for individual identification are using visual identification, personal information (such as height, build, age, presence or absence of hair), medical information (such as scars, tattoos, birthmarks, implants, amputations, prosthesis), footprint records from a chiropodist/podiatrist, clothing, personal effects, fingerprints, DNA profiling and dental identification.4 Identification by dental means gains more importance because the dental tissues are often preserved even if the deceased person is skeletonized, decomposed, burnt or dismembered. Dental tissues are often used to determine age, sex, and ethnicity of the person who can either be a victim or a suspect.4
Data collection methods and supplementary technologies used in forensic dental identification have undergone significant transformation. Conventional methods used in the forensic odontology includes dental record maintenance, dental imaging techniques, bite-mark analysis, DNA analysis using oral tissues, cheiloscopy, and rugoscopy.
The recent concepts includes
DNA analysis
Facial reconstruction
Denture identification
Tongue prints and
Comparison microscopes, have been introduced in the field of forensic odontology5
This article provides an insight into the recent concepts used in this field.
Recent concepts in forensic odontology
DNA analysis
Analysis of DNA in forensic dentistry offers a new tool, where as traditional identification methods has demerit due to heat traumatism, or autolytic process. DNA analysis/profiling or DNA fingerprinting reveals the genetic makeup of a person. For DNA analysis, Both genomic and mitochondrial DNA can be used. The biological materials used for DNA typing are blood, bones, teeth, semen, hair and saliva. Teeth are the excellent source of genomic DNA.6 sex of an individual is determined from DNA fingerprint
Various ways of running a DNA fingerprint are as follows:
Polymerase chain reaction
Fragment length polymorphism method
Short tandem repeat typing
Single-nucleotide polymorphism
Analysis of mitochondrial DNA
Analysis of Y chromosome7
The use of techniques based on polymerase chain reaction (PCR) has acquired greater importance in DNA postmortem analysis in forensic cases 6 (Figure 1)7
Teeth as a source of DNA
Teeth are the most durable organs in the bodies of vertebrates. There morphology is well preserved and persist for the long because they are resistance against extreme circumstances.8 Sex of the individual is determined from the very minute quantities of DNA (as little as 20 pg). The hydroxyapatite crystals , component of enamel binds to the DNA and stabilizes it, therefore an abundance of DNA can be obtained from the teeth.9 Amelogenin (AMEL) is one of the major matrix proteins secreted by the ameloblasts of the enamel. Modern DNA extraction methods can isolate genomic DNA from dental cells and the gene amelogenin, which is a sex-linked gene. In addition, microscopic examination of the cells from the pulp can also reveal the presence of Barr bodies in females.10DNA from the teeth can be obtained by
Crushing
Conventional endodontic access
Vertical splitting
Horizontal section
Cryogenic grinding
Crushing gives better results than sectioning as more DNA can be obtained 10 Facial reconstruction and facial superimposition
It is necessary to reconstruct the individual's appearance during life, If the post-mortem profile does not match the tentative identity of the deceased. Forensic artists utilize the dental profile to help the facial reconstruction. 11 (Figure 2) 12
Figure 2
Steps of manual method of forensic facial reconstruction: (a) replicated skull with landmarks and already constructed eye socket and nose structure (b) advanced reconstruction of the soft facial parts, (c) crude model of the face
The cranial appearance is very much helpful in determining the sex of the individual. Computerized facial reconstruction method uses a laser video camera interfaced with a computer or with CT scanning. Skull data are then imaged as a fully shaded 3D surface. The face can be drawn with the help of computer software (for e.g., Vitrea 2.3 version volumetric visualization software). 3D-CT imaging has been found to be more accurate than imaging performed directly on CT slices and 2D-CT image reconstruction. Although exact picture of the face may not be made, this method splendidly helps in identifying the individual.13
Methods of facial reconstruction
Forensic facial reconstruction can be achieved by two basic techniques. These are 2D and 3D facial reconstructions. 3D computed tomography (CT) imaging has been found to be more accurate than imaging performed directly on CT slices and two-dimensional (2D) CT image reconstruction.13 Each of them is again divided into manual and automated/computer-aided methods.
Manual method
These methods were 2D and 3D employing impressions and clay modeling techniques. In this technique, the impressions of skull were made, and casts were fabricated over which different landmarks pins were applied. These methods were relatively simple but had a few limitations. They were time-consuming, technique sensitive, and expensive.
Limitations
Technique sensitive
Requires highly trained specialists for the interpretation of obtained images13
Denture identification method
Victims missing with all of their teeth lack the important informations, in such circumstances the only identifiable remains are the victim's dentures. A denture as such without any markings is of less or no use in forensic dentistry. The dentures can reveal the positive identity of a person, only if it is marked.14 (Figure 3)15
Labeling the denture is one of the easiest and reliable methods of identification. Methods of denture labeling falls under two categories:
Advantage: more permanent
Disadvantage It can weaken the denture structure and create porosity.
Both the methods of denture marking can be incorporated in full and partial dentures, mouth guards and removable orthodontic appliances.16
Tongue prints
Tongue morphology is unique for each and every individual. For this technique to be successful, the antemortem photograph or impression of the tongue should be available. The lingual impression together with its photographic image may constitute secure methods for forensic dentistry identification, in addition to rugoscopy and cheiloscopy.17 (Figure 4)6
Methods of recording tongue prints
Basic features of the tongue such as color, surface texture, mobility, and any other special characteristics can be inspected by
Simple visualization
Alginate impression followed by cast preparation can be used
Obtaining digital images of the tongue using digital software
Sublingual vein analysis
Histological examination18
The tongue prints of humans is considered in biometrics family. Tongue biometric template can be made using three views such as left lateral view, right lateral view, and profile view. Extraction of tongue algorithm of collecting points gives efficient template for shape of the tongue whereas for texture analysis, normalized histogram with Scale Invariant Feature Transform is used. Matching is done by combining both the extraction techniques templates.19
Comparision microscope
The forensic technology has developed a prototype Virtual Comparison Microscope (VCM). The comparison microscope is a device which helps in analyzing the specimens simultaneously. It consists of two microscopes connected by an optical bridge, which has a split view window. VCM utilizes images of deformed bullets, bullet fragments, and various types of rifling from the company's Bullet Trax-3D system. With the VCM, it is easy to find significant markings in any direction while maintaining a consistent appearance.21
Conclusion
Forensic odontology is an upcoming branch of dentistry with a lot of scope for development. Scope of forensic odontology make unique contributions in the administration of law and justice, which plays a major role in investing and interpreting the dental evidence. Each dental professional has a responsibility to understand the forensic involvements associated with their dental practice. The practicing dentists and the dental students should be made aware of the available technologies and its use in forensic dentistry. New researches have to be encouraged in the field of forensic dentistry which will pave way for incorporating newer technologies in establishing the human identity.
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