Forensic dental identification most of the times are dependent on the availability, adequacy, and accuracy of ante-mortem dental records. Maintenance of dental records is the duty of a dentist and is an essential component, serving as an information source for the dentists and the patients, in medico-legal, administrative, and for forensic purposes. Identification by comparative dental analysis plays an important role similar to fingerprints and DNA analysis.
The dental records were successfully utilized in many disasters such as world trade center disaster, Indian Ocean tsunami disaster in December 2004, etc. Dental records are available in various forms such as dental notes, dental charts, radiographs, photographs, and models. Maintenance of these records is mandatory in the Western countries. Different countries have different guidelines regarding the retention of dental records.
Computer-generated dental records gain more importance due to the fact that it can be easily networked and transferred for routine professional consultation or forensic cases requiring dental records for identification. It is accepted that whenever sufficient characteristic features between the pre- and post-mortem data are available and are identical with explainable differences if any, then it is considered as a positive identification.
In cases where previous records are not available for comparison, an alternative aid used for individual identification is radiograph. The radiographic images of the deceased can be obtained and compared with the available antemortem radiographic image of the suspected person. Historically, the use of radiographs in forensic sciences was introduced in 1896, just a year after the discovery of X-ray by Roentgen, to reveal the presence of lead bullets inside the head of a victim. Dental radiographs are easily available and serve as a vital clue for forensic identification. The parameters used in dental radiographs are shape of the teeth and roots, teeth present, missing teeth, residual roots, supernumerary teeth, non-carious lesions such as attrition, abrasion, fractures, bone resorption due to periodontal disease, bone pathology, diastemas, dental caries, endodontic treatment, intraradicular posts, intracoronal posts, and dental prostheses. Conventional radiography allows observation of coronal shape and size, pulp anatomy, crestal bone, etc. Computed tomography (CT) images reveal the cross-section of the areas exposed and produce multiple images. Antemortem CT images provide information which can be used in the construction of a postmortem facsimile image, considering that craniometrical points can be precisely located and measurements can be accurately performed. The frontal sinus configuration is peculiar to each individual which can be used as a parameter for individual identification. The parameters used for comparison of frontal sinus images are variations in its size, shape, symmetry, border outline, and number and presence of septa and cells.
The digital imaging techniques such as radiovisiography allow accurate analysis of the spatial relations of teeth roots and supporting structures on ante- and post-mortem images. Many soft wares have been developed which helps in rotation of the images, translation, and scaling, facilitating the exact alignment between ante- and post-mortem radiographs which eliminate the necessity of new exposures. Thus, the use of radiographic techniques provides the hidden dental information for the use in forensic odontology.
Facial photographs, video recordings, or smile photographs that show specific characteristics of each individual also serve as a valuable aid in forensic identification. In this manner, orthodontics serves as a source of extensive clinical documentation of the dental tissues that determine the smile of individuals. The increased use of extra- and intra-oral photographs for the planning and execution of treatments, along with the popularization of digital cameras, is providing more data for forensic human identification.
Bite marks on human tissues can be observed in violent incidents such as sex-related crimes, child abuse cases, and offenses involving physical altercations, such as homicide. It can occur in instances where the attacker bites the victim or the victim bite the attacker as an act of defense, but it should be remembered that the bite victim could be the suspect in the cases. Male victims are most often bitten on the arms and shoulders, while female victims are most commonly bitten on the breasts, arms, and legs. The biting surfaces of the individual groups of teeth are unique and related to the function. And also, it shows individual characteristics such as fractures, rotations, missing, or extra teeth. In addition, the width of the dental arches could be related to the age of the attacker.
The anatomical location, severity, and quality of the bite marks have significance in the identification of the individual. The information such as demographics (name, age, sex, date, etc.), location, size, shape, color, type of injury, and swabs should be collected from the bite victim. In case of bites which are not visible to the naked eye, demonstration using ultraviolet light illumination technique can be performed. The collection of evidence from the bite suspect must have a proper consent, detailed history, photographs, the details of extra- and intra-oral examination along with high-quality impressions of the upper and lower arches. The process of comparing bite marks includes analysis and measurement of size, shape, and position of the individual teeth. The fabrication of overlays is the most common comparison method used. The methods used to fabricate overlays are hand tracing from study casts, hand tracing from wax impressions, hand tracing from xerographic images, the radiopaque wax impression method, and the computer-based methods such as using the image perception software.In addition to all these methods, salivary DNA recovery and bacterial genotyping from the bite marks are the most recent ones and have become the backbone of forensic investigation.
Forensic Dentistry has contributed remarkably to human identification processes. DNA analysis is a new tool used in the field of forensic odontology, it gains importance when conventional identification methods fail due to the effects of heat, traumatism or autolytic processes, distortions, and difficulties in analysis. There are many biological materials such as blood, semen, bones, teeth, hair, and saliva that can be used to accomplish DNA typing. With the advent of polymerase chain reaction which allows enzymatic amplification of a specific DNA sequence even in a negligible amount of source material, forensic identification using DNA analysis becomes increasingly popular with investigators.
The currently performed DNA profile tests are reliable and provide information about the physical characteristics, ethnicity, place of origin, and sex of the person. In courts, these tests are accepted as legal proofs such as for investigation of paternity and human identification. Some of the advanced techniques in DNA profiling are Restriction Fragment Length Polymorphism Typing, Short Tandem Repeat (STR) Analysis, Y-Chromosome Analysis, X-Chromosome STR, Single Nucleotide Polymorphism Analysis, mtDNA Analysis, Gender Typing and DNA methylation analysis.
Dental professionals can carry out investigations involving biological materials derived from the human body in various conditions (quartered, dilacerated, carbonized, macerated, putrefied, in skeletonization and skeletonized), with the aim of establishing human identity.
Fingerprints have been historically used for identification. However, in some situations, such as fire and skeletonization, they are easily destroyed. In addition, experts frequently need to use comparative elements of the victim produced prior to his/her death, such as the dental records, to carry on the identification. However, this documentation may be unavailable or incomplete. At present, with the application of biomolecular resources for human identification, it is possible to identify a person using small amounts of deteriorated biological material, conditions that are relatively frequent in forensic analyses. This fact could be demonstrated after the South Asian tsunami disaster on December 26th 2004, when the most varied techniques were applied for identification of thousands of victims, such as forensic pathology, forensic dentistry, DNA profiling and fingerprinting. Even though, 99% of the bodies were identified using dental records or fingerprints and only 1% of forensic identification was made by DNA profiling.
The main exogenous factors that may limit the retrieval of information from body remnants and restrict the processes of human identification are the elements present or associated with fire, such as flames, heat and explosions. In this sense, the teeth play an important role in identification and criminology, due to the high uniqueness of dental characteristics in addition to the relatively high degree of physical and chemical resistance of the dental structure. Due to their capacity of enduring environmental changes, the teeth represent an excellent source of DNA because this biological material may provide the necessary relation for identification of an individual in case of failure of conventional methods for dental identification. In fact teeth act as major source of DNA because of its ability to withstand changes, they are better sources of DNA than skeleton bones.
Teeth are an excellent source of genomic DNA. DNA is found in vascular pulp, odontoblastic process, accessory canals, and cellular cementum. Dental pulp can also be used for DNA analysis and is good source for determination of blood groups. The presence of ABO blood grouping antigens in soft and hard tissues makes it possible to determine blood group of highly decomposed remains. The DNA from the teeth is not only acts for primary identification but it can also be used as reference sample to relate the other tissue fragments. When there is no information about ante-mortem of the individual, the specimens can be selected from spouse and children as reference sample for DNA testing. Forensic odontology has an important role because teeth and saliva is excellent source of DNA. Since 1992, the isolation of DNA from saliva and salivary stained material is done.
The genomic DNA is found in the nucleus of each cell in the human body and represents a DNA source for most forensic applications. The teeth are an excellent source of genomic DNA because PCR analyses allow comparing the collected postmortem samples to known antemortem samples or parental DNA.
Newer DNA tools, including mitochondrial DNA and SNP (single nucleotide polymorphism – replacements, insertions or deletions that occur at single positions in the human genome), might be used when STR typing fails to yield a result or when only a partial profile is obtained due to the size and conditions of the sample. Poor quality DNA can be found, for example, in mass disaster, such as the World Trade Center attacks, airplane crashes, tsunamis and decomposing bodies.
The genomic and mitochondrial DNA (mtDNA) are used for body identification. The genomic DNA is found in the nucleus of each cell in the human body. Although DNA undergoes progressive fragmentation through autolytic and bacterial enzymes; the sequence of information is still present in the DNA fragment even in the decomposed post-mortem tissue. mtDNA can be used when the extracted DNA samples are too small or degraded, such as those obtained from skeletonized tissues. The likelihood of obtaining a DNA profile from mitochondrial DNA is higher than that with any marker found in genomic DNA. The amplified DNA is then compared with the ante-mortem samples such as stored blood, hairbrush, clothing, cervical smear, and biopsy specimens. Therefore information is not completely lost even though the body has undergone decomposition.
The analysis of mitochondrial DNA for forensic purposes is restricted to ancient tissues, such as bones, hair and teeth, in which the nuclear DNA cannot be analyzed. However, this examination is performed by direct sequencing of its nitrogenous bases, which is a very expensive technique because it employs a highly specialized technology. Furthermore, mitochondrial DNA is exclusively matrilineal and hence less informative. Thus, this analysis is not usual in all forensic laboratories directed at resolution of crimes and identification of persons.
The study of DNA (genomic and mitochondrial) is usually performed by STR (short tandem repeats) analysis, which can be defined as hypervariable regions of DNA that present consecutive repetitions of fragments that have 2 to 7 base pairs (bp). The VNTR (variable number of tandem repeats) testing, which may present short repeated sequences of intermediate size (15 to 65 base pairs), is rarely used in forensic analyses due to the poor quality DNA provided with this method. The most valuable STRs for human identification are those that present greater polymorphism (greater number of alleles), smaller size (in base pairs), higher frequency of heterozygotes (higher than 90%) and low frequency of mutations.
The environmental influence on the concentration, integrity and recovery of DNA extracted from dental pulps was studied keeping in mind the pH (3.7 and 10.0), temperature (4ºC, 25ºC, 37ºC and tooth incineration), humidity (20, 66 and 98%), type of the soil in which the teeth were buried (sand, potting soil, garden soil, submersion in water and burying outdoors) and periods of inhumation (one week to six months). And the ultimate conclusion was that the environmental conditions examined did not affect the ability to obtain high-molecular-weight human DNA from dental pulp.
In addition to human identification, another subject of study of Forensic Dentistry related to molecular biology is the analysis of bite mark evidence. In cases of physical assault, such as sexual abuse, murders and child abuse, bite marks are frequently found on the skin. The aggressor's saliva is usually deposited on the victim's skin during biting, kissing or suction. It is possible to identify the aggressor's blood group by the ABO system in 90% of cases, but this method is not very informative and would not be used if DNA amplification techniques, such as STR profiling, are available. From these cells, it is also possible to isolate DNA for identification of the aggressor.
Initially, the forensic community used VNTR testing for body identification and paternity tests. However, as this method requires a large amount of material and has low-quality results, several cases could not be solved, especially when only little biological material samples were colleted in a scene crime investigation. The introduction of the polymerase chain reaction (PCR) technique, which makes possible the amplification of small DNA samples, widened the scopes in Forensic Genetics. STR testing started being used for forensic casework, making a revolution on human identification and paternity tests.
In Polymerase chain reaction (PCR) technology, the Streptococcal DNA sequence provides a means with which to identify the bacterial composition from bite marks and can be matched exclusively to those from the teeth responsible. Saliva a major source of DNA; contains sloughed epithelial cells from oral mucosa and inner surface of lip. The enzymes such as Streptococcus Salivarius and Streptococcus Mutans are present on teeth and in the saliva. DNA from saliva surrounding the area of the bite mark is a reliable form of identification. DNA sampling has been included as a task for a forensic odontologist. Dental structures can provide a source of DNA for easy identification. Due to this abundance of material, the use of the technique based on PCR (Polymerase Chain Reaction) has acquired great importance in DNA post-mortem analysis in forensic cases.
Several studies are currently being conducted in order to optimize the methodology of DNA extraction from the saliva deposited on the skin to be used as evidence in forensic cases, such as the double-swab testing. This examination allows establishing DNA profile in 4 of 5 tested samples composed of 250 µL of saliva deposited on the skin. In addition to gathering cells from the human body itself, it is also possible to retrieve cell samples from objects that had contact with the body, which are called artifacts. DNA can be isolated in sufficient amount for human identification by examination of chewing gums, cigarettes, bite marks in foods, among others.
As observed, several protocols are used for DNA extraction and analysis, and there is no standard methodology. Therefore, researchers must carefully evaluate the conditions of the material to be examined, especially when dealing with forensic cases, in which there is a greater risk of sample contamination and influence of environmental factors, in addition to a small amount of material available in most situations.
The PCR technique has been the usual choice for investigation of the frequencies of STRs. This technique allows amplification of restricted regions of the human genome, associated with genomic hybridization. Recent developments of the technique of length amplification of polymorphic fragments have enhanced the potential of analysis of forensic samples. The PCR method enables differentiation of an individual from another, with a high level of reliability and with about 1 ng (one one-billionth of a gram) of the target DNA.
Those intending to use the PCR technique as a working tool must pay attention and accuracy during sample handling as well as, follow strict policies to prevent contamination. In practice, steps aiming at reliable results that might contribute to elucidate forensic cases are the adequacy of collection procedures, verification of the conditions of the collected material, choice of methodology for DNA extraction and analysis, and, finally the analysis of results. It should be mentioned that DNA extraction is a process composed of 3 different stages: cell rupture or lysis (which allows use of several techniques for effective rupture of the cell membranes), protein denaturation and inactivation (by chelating agents and proteinases in order to inactive elements, such as proteins), and finally DNA extraction itself. The techniques of DNA extraction most often employed in Forensic Dentistry are the organic method (composed of phenol-chloroform and used for high molecular weight DNA, with a higher likelihood of errors, given the use of multiple tubes); Chelex (the fastest with the lowest risk of contamination, yet very expensive); FTA Paper (composed of absorbent cellulose paper with chemical substances, which speed up its use); AND isopropyl alcohol (containing ammonium and isopropanol, which is less expensive and also an alternative to the organic method).
An important observation is when degraded sample in the ancient DNA are the only artefacts, being necessary using techniques to overcome the problems of contamination and degradation of DNA sample. The factors leading to the degradation of DNA include time, temperature, humidity (facilitating the growth of microorganisms), light (both sunlight and UV light) and exposure to various chemical substances. Combinations of these conditions are often found in the environment and tend to degrade the samples into smaller fragments. Therefore, once a sample has been collected, it must be dried (or remain dry), depending the type of biological material. It may also be stored frozen (if necessary), although for DNA this is less important than for the conventional protein and enzyme systems. The sample should not be subjected to fluctuations in either temperature or humidity.
Violence and crimes against human life, such as bomb explosions, wars or plane crashes, as well as cases of carbonized bodies or in advanced stage of decomposition, among other circumstances, highlight the need to employ ever faster and more accurate methods during the process of identification of victims. In such cases, teeth represent an excellent source of DNA, which is protected by epithelial, connective, muscular and bone tissues in case of incineration. Additionally, the dental pulp cells are protected by enamel, dentin and cementum hard dental tissues. Therefore, dental professionals working on the field of Forensic Dentistry should incorporate these new technologies in their work, as several methods are available for DNA extraction from biological materials, yet standardization of the protocols adopted for such purpose has not been reached so far. For this reason, studies on molecular biology applied to human identification will probably further enhance DNA extraction with less material available and under increasingly adverse conditions.
Cheiloscopy is a forensic investigation technique which deals with identification of humans based on their lip traces. Lip print wrinkle pattern has individual characteristics same as finger prints. Lip prints are normal lines and fissures in the form of wrinkles and grooves present in the zone of transition of human lip, between the inner labial mucosa and outer skin, examination of which is known as cheiloscopy. Lip prints provide sufficient information for forensic investigations as the lips also possess furrows and grooves.
These wrinkles and grooves on the labial mucosa form a characteristic pattern. Lip print recording is helpful in forensic investigation that deals with identification of humans, based on lip traces. The presence or absence of a person from the crime can be verified based on lip prints since the lip prints being uniform throughout the life. The 1967 Santos was the first person to classify lip grooves. There are four types of lip grooves.
Lip prints can be obtained at the crime scene either directly from the lips of the deceased or from the clothing, cups, glasses, cigarettes, windows, or doors. Lip prints have to be obtained within 24 hour of death to prevent erroneous data that would result from postmortem alterations of lip. Lip print pattern depends on whether mouth is opened or closed. In closed mouth position, lip shows well-defined grooves; whereas in open mouth position, the grooves are relatively ill defined and hard to interpret.
Pathology of the lip such as mucocele, postsurgical alterations, loss of support due to loss of anterior teeth, presence of debris or fluid on the lip surface, application of a thick layer of lipstick, or over stretching of cellophane tape can alter lip print recording.
Recent studies have proven lip prints as a superior tool compared to fingerprints and mandibular canine index in gender determination. For collection, development and recording of lip prints a uniform and standard procedure has to be developed which helps ensuring comparison. Lip prints can be obtained using cellophane tape or a scotch tape which are pressure sensitive.
In case of teeth loss, due to reasons such as trauma, palatal rugae pattern serves as an alternative method for identification because of its uniqueness. As rugae is internally placed in the oral cavity and is protected by tongue and buccal pad of fat, it remains undisturbed from heat and other assaults. The study of the patterns of the grooves and ridges (rugae) of the palate to identify individual patterns is called as Rugoscopy. The pattern of these rugae is considered unique to an individual and can be used as reliable method in postmortem cases.
Materials and methods used to analyze the rugae patterns includes, photographs and impression of maxillary arch, computer software programs (for e.g., RUGFP-ID), calcorrugoscopy or overlay print, stereoscopy (through which three-dimensional [3D] image of palatal rugae can be made), stereophotogrammetry (which is comparatively accurate).
Forensic professionals work for identifying the recovered human remains (identification of whole or fragmented bodies). Most often in major disasters and in accidents, the body of the dead person may be decomposed or skeletonized. In such cases, the only part retained may be the skull and the other bones. Skulls can remain unaltered even for millions of years and can provide an inimitable means of identification. The cranial appearance is very much helpful in determining the sex of the individual.
Face reconstruction is the reformation of a person based on anatomic characteristics of the skull. It requires adequate stages and it is a combination of artistry and anatomy. The ultimate aim of all facial reconstructions for forensic purposes is to recreate an in vivo countenance of an individual, normally when no other identifying evidence is available, bearing a sufficient visual resemblance to the missing or deceased person, so that it may contribute to their recognition and lead to identification. Forensic artist utilizes the ante mortem photograph of dental profile to help in facial reconstruction. In most of cases the clues found on the crime site can be helpful to construct the face like dress size, other clothing may indicate the gender of the individual, hair may be present, skin tag to determine the color and racial species.The method is based on the knowledge of facial soft tissue thickness measured at selected anatomic landmarks as well as knowledge of particular morphologic features. It is possible to reconstruct the face from an identified skull.
Today, 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.
Victims possessing all or most of their dentition can be identified using their teeth through various methods, whereas those missing all of their teeth lack such information. 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. Labeling the denture is one of the easiest and reliable methods of identification. Methods of denture labeling falls under two categories: the surface marking method and the inclusion method.
The surface marking methods include scribbling or engraving the denture and marking with embossed letters. Inclusion methods include metal identification bands, computer-printed denture micro-labeling system, lead paper labeling, embedding the patient photograph, denture bar coding, T-bar, laser etching, lenticular card system (using a polyethylene terephthalate, in which the first flip shows patient's name, sex, and age, and the second flip shows address and driving license number, when viewed from a different angle), radiofrequency identification tags, electronic microchips.
Both the methods of denture marking can be incorporated in full and partial dentures, mouth guards and removable orthodontic appliances. Among these two categories, the surface methods are easy to apply and relatively inexpensive. The only disadvantage is they worn off easily and needed to be reapplied. Whereas, the inclusion methods are more permanent; however, it can weaken the denture structure and create porosity.
The use of microscopes in forensic sciences has an impact on the accuracy. Examination of teeth under microscope can confirm sex by the presence or absence of Y-chromatin. The phase contrast microscope is useful in analyzing the cemental annulations for age estimation. In case of comparison of the samples, the conventional microscope consumes more time in readjusting the focus and in achieving different views. Moreover, the observer has to rely on memory when comparing two objects.
To avoid these problems, 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 BulletTrax-3D system. With the VCM, it is easy to find significant markings in any direction while maintaining a consistent appearance.
Tongue is unique to each person in its shape and surface textures and is the only internal organ that can be protruded from the body and easily exposed for inspection. Use of tongue prints for forensic identification is at budding stage now. For this technique to be successful, the antemortem photograph or impression of the tongue should be available.
The lingual morphological aspects can be preserved using the alginate molding technique for duplicating the minute details which are unique for each and every individual. The lingual impression, together with its photographic image, may constitute secure methods for forensic dentistry identification. The tongue prints present in the human tongue recently becomes a new member of the 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.
Forensic odontology relies on scientific methods as they relate to the teeth and jaw. This may include the study of dental anatomy and the interpretation of radiographs, pathology, dental materials, and developmental abnormalities. Because the teeth are some of the strongest elements of the human body, odontology may be performed even when the body has been destroyed.
Due to the importance odontology plays in everything from criminal convictions to the identification of missing persons, Indian Dental Association (IDA) is increasing awareness and educational courses for this increasingly significant field of forensic science.
As a doctor of dentistry, a forensic dentist must possess a Doctor of Dental Science (DDS) degree. However, beyond that, forensic dentists must achieve training specific to the field of forensic science. Many forensic dentists receive the bulk of their training through courses, lectures, training and demonstrations.
Because of the need for forensic dentists to achieve training specific to the field of odontology, professional certification through Indian Dental Association (IDA) educational platform as it allows forensic dentists to demonstrate their knowledge of forensic science and forensic odontology.
While Forensic Odontology is an interesting option, it is indeed very essential to know what are the skills expected of a forensic odontologist.
Forensic odontologists, known informally as forensic dentists, apply dental knowledge to legal matters. They use dental records to identify unknown human remains, identify criminal assailants in cases involving biting by comparing dental records with bite marks left on a victim, and testify in civil and criminal cases requiring dental expertise. Forensic odontologists can work in a variety of settings, including dental schools and medical examiner's offices. Many, however, operate regular dental practices and work as consultants on legal cases.
A medical examiner is a forensic pathologist, or a medical doctor who conducts autopsies to determine cause of death. The medical examiner also may collect and analyze physical evidence from victims of rape and assault. Some medical examiner's offices may employ forensic dentists on a permanent or consulting basis to identify remains with dental records or conduct bite mark analysis.
Some forensic odontologists work for insurance companies as investigators in cases involving dental or medical insurance fraud.
Many forensic odontologists work on a consulting basis, providing their services when requested by law enforcement agencies, district attorneys, and private detective agencies. When not doing forensic work, they may work as part of full-time dental practitioners, or teach at a dental school.
Many forensic odontologists work for Police Department, Crime Branch, Forensic Science Laboratories, Banks, Defence/Army, Narcotics Dept, Universities, Hospitals or Organizations.