Keywords
forensic dentistry - disaster victims - inventions - dental prosthesis - three-dimensional
printing
Introduction
Forensic odontology (or forensic dentistry) is defined as the branch of dentistry that addresses the proper handling and examination of dental
evidence and the evaluation and presentation of dental findings in the interests of
justice. Forensic odontology has become a fundamental part of large global forensic educational
establishments such as American Academy of Forensic Sciences along with International
Association of Identification.[1] The identification of individuals in cases of mass disaster is complex due to severe
disfigurement, charring, and decomposition.[2] Antemortem and postmortem records are retrieved and correlation is done to set up
an accurate identification. Most of these antemortem dental archives comprise of dental
and medical histories, radiographs, written notes, study models, diagrams, clinical
photographs, results of specific trials, prescriptions, charts, and referral letters.[3] Dental identification can have applications such as comparative identification where
postmortem dental records are compared with antemortem dental records to identify
the person, to obtain identification of person where antemortem records are not available,
and to identify victims of mass catastrophes.[4]
Teeth are resistant to desiccation and decomposition and are one of the last tissues
to disintegrate after death, attaining substantial significance in forensic investigations.[5] Electronic record keeping has reduced the loss of data that is usually encountered
with conventional methods.[6] This review article intends to provide a general overview of the importance of forensic
odontology with an emphasis on the different approaches for identification in a legal
context.
Discussion
The analysis, handling, and presentation of dental evidences for legal matters are
the main focus of forensic odontology. Single body recognition, disaster victim identification,
estimation of age, and bite mark identification are the four primary aspects of forensic
dentistry.[7] The differentiating factor between the known distinctive features of missing individual
(antemortem data) with that of retrieved findings from an unknown body (postmortem
data) forms the basic groundwork of “identification” and diagnosis.[6] Since the importance of forensic odontology in the field of judiciary is rapidly
increasing, a thorough understanding of this field appears to be more than justified.
The various techniques and methods applied in the field of forensic dentistry for
identification of individuals are as follows.
Ameloglyphics (Amelo: Enamel, Glyphics: Carvings)
Ameloglyphics (Amelo: Enamel, Glyphics: Carvings)
Automated software has been promoted for the reliable identification of the individuals,
based on biometric based verification methodologies such as iris scanning, fingerprint
verification, and recognition of facial features. Teeth are considered hard tissue
analogs to fingerprints as both are unique to every individual. Enamel, the hardest
tissue in humans, is known to show resistance to decomposition. The structural units
of enamel are the enamel rods that form unique patterns. Millions of enamel rods can
be seen in each tooth and their number varies from tooth to tooth. Longer enamel rods
are found at the thicker portions, that is, cuspal area and shorter rods in the thinner
portions, that is, cervical area. Ameloglyphics is the study of patterns of these
enamel rods. Patterns of ends of the enamel rods found at the surface of tooth are
known as tooth prints.[5] Common methods to replicate these enamel rods are cellulose acetate paper, cellophane
tape, and rubber base impression materials. Study of dental hard structures is made
possible by means of peel that is a replica of 10% orthophosphoric acid etched mineral
surface, that is, the enamel surface to study the enamel rod end pattern which is
a unique pattern in all individuals. Peel is examined under a microscope with the
incident or transmitted light. Modifications were done to study dental hard structures
due to their unique mineralogical composition.[2]
A study by Christopher et al showed that these prints can be preserved for 4 to 5
months making them a consistent and valued tool for identifications in forensics.
The study had its limitations as tooth prints may be unique to individuals only if
the derived tooth prints were taken from a specific site from a particular tooth.
Any mild changes either in the orientation or direction of the tooth prints can interfere
while recording results in obtaining a new pattern from the same individual and from
the same tooth site.[5]
Dental Radiographs
The dental radiographs are usually observed to compare findings between antemortem
and postmortem radiographs including curvatures of roots, buried tips of roots, root
canal treated teeth, and shapes of restoration with presence or absence of base underneath.
Radiographs also reveal normal anatomy of tooth along with its anomalies, jaw bones,
and sinus. Digitized dental radiographs can be superimposed to compare parameters
such as spatial relationship of supporting structures of roots and teeth in antemortem
and postmortem records. Such superimposed radiographs can be used for identification
at certain stages of development of human dentition.[3] In cases of antemortem records that are not accessible, the deceased’s postmortem
chart is used in excluding an individual’s identity by comparing with the available
antemortem archives of other individuals.[8] Collection of postmortem-radiographic image is affected by factors such as the availability
of appropriate dental X-ray apparatus, rigor mortis, aiming of X-ray beam toward the
victim’s body, and electrical supply in the working area. Age estimation techniques
also utilize volumetric pulp tooth ratios extracted through three-dimensional (3D)
reconstructions of cone-beam computed tomography images.[9]
Estimation of Dental Age
Demirjian et al furnished the developmental stages of teeth used in the assessment
of chronological age.[1] Johnson’s method of estimation of age with a single tooth in adults is a modification
of Gustafson’s method involving several phases of deteriorating changes in the tooth
such as attrition of the occlusal aspect, the loss of periodontal attachment, formation
of secondary dentine in the coronal aspect, apposition of cementum, and resorption
at apex and root transparency. Kvaal et al proposed an alternate technique of age
estimation in adult patients through the measurement of pulp size from periapical
radiographs of the tooth depending on the gender of an individual.[1]
Bite Mark Evidence
The identification and comparison of bite marks to the dental characteristics of the
suspect are a contribution of dentistry to forensics.[8]
[10] Bite marks can be observed in cases such as homicide, assault, and physical or sexual
abuse. In addition, victims may also possess bite injuries from nonhuman sources.
Generally, animal bites remain distinguished from injuries inflicted by human bites
by differences seen in arch alignments and specific tooth morphology. Most animal
bites cause shear injuries thus inflicting open wounds with lacerations of the skin
distinguished by forensic odontologist by their different arch alignment and morphology
of specific teeth.[8]
Presentation of Bite Marks
Bite marks can be recognized as a semicircular shaped injury that comprises two separate
arcs, that is, one arc of the upper arch and the other of the lower. The central area
of bite mark either has an absence of injury or may be seen with a diffuse bruise.
Factors influencing the severity of a bite mark injury may include force of infliction
of the original injury, the anatomical location bitten, and the time elapsed between
infliction.[10]
Collection of Bite Mark
An influential item of evidence from a bite victim is photographs. Such photographs
are to be taken at 90 degrees to the injury at a frequency of 24-hour interval regularly,
with a camera on both the departed and the living victim to record its appearance.
Subsequently, a thorough dental examination should be taken followed by a dental charting
that clearly depicts the detailed presence and condition of each of the teeth, its
modifications, and any restorations if undertaken. The next step is recording impressions
of both the arches using the highly recommended impression material, poly-vinyl siloxane,
combined with plastic stock trays. “Double swab” technique proposed by Sweet allows
the maximum collection of DNA from the saliva deposited during the biting process.[10] Bite mark seen on a nonhuman substrate such as perishable items should be photographed
carefully, followed by swabbing and finally an impression must be taken thus allowing
a “docking” analysis to be conducted followed by long term storage in a freezer.
The American Board of Forensic Odontology has provided a set of points to establish
the injury status of a bite mark: (1) exclusion—the injury does not include a bite
mark; (2) possible bite mark—biting cannot be ruled out as the injury shows a pattern
that may be caused by teeth, but might also be caused by some other factors; (3) probable
bite mark—pattern that strongly suggests or supports origin from teeth but could conceivably
be caused by something else; (4) definite bite mark—pattern that confirms that teeth
created the pattern of bite mark.[10]
Tongue
Analysis of the texture and shape of dorsal surface of tongue is significant as it
reveals noteworthy morphological details proving its uniqueness as a tool in personal
identification. Preservation of morphological aspects of the lingual surface of the
tongue is achieved by the alginate molding technique for the duplication of minute
subtleties exclusive for every individual. The lingual impression is recorded by means
of neo colloid impression material that is applied steadily from the level of oral
commissure to the tip of lingual aspect thus overcoming the regurgitation reflex.
Obtained lingual impression along with the photographic image may establish a dependable
method for forensic identifications. A relevant positive image is acquired with the
resulting molds with type III dental stone.[11] Biometric template of tongue consists of left and right lateral view and profile
view. The normalized histogram with scale-invariant feature transform is used for
analysis of tongue texture. Combination of templates of tongue algorithm and normalized
histogram extraction techniques results in matching.[12] For recording minute details and 3D analysis of tongue, alginate impressions followed
by cast preparation is done, the alternation of which includes sublingual vein analysis.
Placement of an ultrasound transducer in the sublingual area helps in assessing the
function of the tongue. In case of tongue analysis, its histological examination can
be utilized.[11]
Palatal Rugae—Landmark for Forensic Diagnosis
Palatal Rugae—Landmark for Forensic Diagnosis
Palatal rugae are made up of connective tissue in the form of irregular ridges across
the front portion of the palate and are often used as individual markers for biometric
identification due to their unique features. Palatoscopy can be used in the necro
identification in various mishaps of aeronautical origin to guarantee identity of
pilots by means of antemortem records.
Following methods are commonly used to analyze the rugae patterns: (a) collection
of photographic images and impressions of maxillary arch; (b) calcorrugoscopy that
comprises the overlay print of palatal rugae in a maxillary cast to accomplish a comparative
analysis; (c) computer-based software programs (e.g., RUGFP-ID); (d) stereophotogrammetry
by a device called Traster Marker that permits accuracy; (e) stereoscopy through which
3D pictures of palatal rugae can be gained and is dependent on investigation of two
unique pictures captured from two different focuses.[12]
Thomas and Van Wyk traced patterns of rugae from antemortem as well as postmortem
dentures onto clear acetate for the purpose of superimposing such tracings onto the
photographs of plaster models.[13] Lately, Limson and Julian developed a PC software program based on the principle
of fingerprint analysis.[13] This program evaluates the points plotted on medial and the lateral extremities
of all rugae and the obtained information is sequentially stored corresponding to
the pixel position with an accuracy of 97% in a mock antemortem and postmortem comparison
of rugae of the palate. Possible pattern changes of rugae may be under the influences
of cleft palate surgery, forced eruption of canines, extraction of adjacent teeth,
orthodontic movement, periodontal surgery, or finger sucking in childhood.[13]
A study conducted by De Angelis et al for identification purposes found that the normal
growth of an individual does not change the characteristic features of his palatal
rugae.[14]
Lips
Lips possess furrows and grooves. Santos classified lip grooves in 1967 as straight,
curved, angled, and sinusoidal lines respectively.[15] Cheiloscopy is a technique used in forensic odontology to identify individuals using
lip tracing. Direct retrieval of lip prints is acquired from lips of the deceased
and indirectly from inanimate objects. Lip print patterns should be traced within
the first 24 hours of death, based on the position of mouth, to avoid any incorrect
data arising from postmortem alterations of the lip of the deceased. Distinct grooves
are seen in closed mouth position, whereas in open mouth position the grooves are
poorly defined causing difficulty in interpretation. The various pathologies associated
with lips such as mucocele, loss of anterior teeth resulting in loss of support, presence
of fluid or debris on the lip surface, and postsurgical variations can result in alterations
while recording lip prints.
Various Methods to Record Lip Prints
-
Use of a roller fingerprint.
-
Overlay tracings made of grooves on the surface of a non-porous mirror.
-
Photographing the suspect′s lips.
Application of appropriate transferable medium to the lips such as lipsticks followed
by pressing the individual’s lips to cellophane tape or a piece of paper. Such prints
can be processed with a conventional powder and developed with a magnetic powder and
magna brush.
Latent lip prints are developed via the magna brush method. The lip prints are pressed
against the surface of a glossy, porous material or a smooth, nonporous material and
allowed to solidify by subjecting them to a heat source. Tsuchihashi classified the
pattern of lip prints into six types as follows: (I) complete straight grooves, (I’)
partial straight grooves, (II) branched grooves, (III) intersected grooves, (IV) reticular
grooves, and (V) undifferentiated grooves.[16] A preliminary study conducted by Furnari et al assessed the interrater dependability
among various forensic odontologists who used Tsuchihashi classification and concluded
that this classification failed to obtain a solid argument for reliability.[16]
Restorations
In cases of bodies burned beyond recognition, identification is possible by in-depth
knowledge of charred dentition of the deceased and residues of restorative material
if any. Teeth are categorized as intact (no damage), scorched (superficially parched
and discolored), charred (reduction to carbon by means of incomplete combustion),
and incinerated (burned to ash) when subjected to variable temperatures and time.[17] Posterior teeth are often associated with restorations and acrylic dentures that
can survive high temperatures.[1] Parts of restored teeth discovered at the crime scene may be used to identify the
victim or the suspect. Other scientific sources such as scanning electron microscopy
(SEM) and energy dispersive X-ray spectroscopy (EDS), and microscopy are used to assist
in recognition and differentiation of tooth related fragments.[18] A study was conducted by Patidar et al to assess the degree of destruction in teeth
structure, shape, and color, restoration and mandible after incineration process.
The study concluded that with a rise in temperature, the decomposition rate of restorative
material increases. The study also stated that resistance of the restoration to variable
temperatures is unique with respect to the material itself and further added that
there is deformation, loss of elasticity, carbonization, and fractures seen with respect
to bones.[17]
DNA
The use of DNA technology gives answers to most of the ethical and legal problems
that have to be addressed systematically.[19] A rich source of DNA is seen within the pulp cavity, coronal portion of pulp chamber,
odontoblastic processes, radicular canals, and the cellular cementum. Since quality
and not quantity of DNA is important, plenty of quality DNA is extracted from the
root region. Cryogenic grinding is currently used to extract high-quality DNA material.[20] Horizontal sectioning, vertical splitting, and normal endodontic access procedures
are strategies introduced for separating DNA and its recovery from human teeth. DNA
isolation is done by organic extraction method or silica-based DNA extraction methods.
DNA can be amplified by polymerase chain reaction (PCR) and real-time PCR methods.[19]
Implants—The Visual Aid
Primary scientific identification of victims is possible using nonvisual methods such
as fingerprint and DNA analysis with dental records. Loss of fingerprint particulars
and denaturing of DNA may be present in cases where the victim has been burnt.[21]
[22] When an unidentified body with no available dental record is found with one or more
implants in the jaws, evidences gathered from the type of implants used could aid
in the investigation.[3] Features of the recovered dental implants may contribute as the lone physical identifying
data that is available because of their physical properties.[3]
[22]
Compared with all other implants, only pure titanium implants showed color variation
when subjected to a high temperature of 1125°C. Any changes in the physical proportions
due to the formation of an oxide layer should be contemplated before any metric investigation.[23]
Crown
Most of the dental crowns are made of porcelain material and the analysis of components
of porcelain assists in identification. Fluorescent examination lamps have been used
to examine the emitted fluorescence of porcelain crowns of murdered victims and compared
with several control porcelain samples. Wave dispersion X-ray microanalyzer evaluates
composition of porcelain crown and that of control sample to upsurge the neutrality
of the results by means of quantitative analysis.[3]
Root Canal Filling Material
Root Canal Filling Material
The details of pre- and postincinerated elemental analysis of various endodontic filling
materials can be used by the forensic odontologist for rapid reference. Bonavilla
et al used SEM or EDS to evaluate the composition of the root canal obturating materials.
This study highlighted that the elemental fingerprints of obturation materials, sealers,
specific files, and cements can be utilized to assist in forensic identifications.[24] The study by Bush et al revealed that big, classy laboratory-based SEM/EDS is typically
not preferred over portable X-ray fluorescence spectrometer (XRF) because the various
materials used in endodontics are readily and positively fingerprinted to perform
the elementary examination of the deceased's postmortem remains. Ideally XRF spectroscopy
suits for investigations that are performed in a contaminated or hazardous field setting.[25]
Dentures and Denture Marking
Dentures and Denture Marking
Millet and Jeannin in the year 2004 implanted a radio frequency identification transponder
within a complete denture of upper arch. The system comprised of a transponder in
addition to a handheld electronic reader. This affords to rapidly identify the deceased
victims since metal restorations show outrageous resistance to every insults.[26] The various methods used for denture marking are listed in [Table 1].
Table 1
Denture marking methods
|
Surface marking methods
|
Inclusion methods (for complete dentures)
|
|
Engraving method
|
Clear acrylic T bar method
|
|
Fiber tip pen method
|
Bar coding method
|
|
Wecker’s electro pen method
|
Radio frequency identification tag
|
|
Onion skin paper method
|
Metallic band according to Swedish guidelines
|
|
Denture bar coding method
|
Microlabeling
|
|
Stevenson’s method
|
Memory card method
|
|
Laser etching method
|
Data matrix code
|
The trained professionals usually incorporate the complete details of the patients
in the dentures by means of denture marking. The disadvantage of such systems is that
the retrieved data from these systems require distinct equipment to read and interpret
the data such as memory card, radio frequency identification, and barcodes as these
cannot be hurriedly obtained in crises such as mass disasters and road accidents.
With altered opinions from the worldwide communal of forensic odontologists, encouragement
for the adoption of a universal plan intending to denture marking and collaboration
is essential.[27]
Oral Jewelry and Piercings
Oral Jewelry and Piercings
Oral piercings and tattoos are increasingly used by youngsters as a fashion statement.
Any form of jewelry that would be left after a mass disaster or an air crash is essentially
used for the purpose of human identification. The various oral jewelry commonly noted
are listed in [Table 2]. As stated by American Academy of Pediatric Dentistry, oral jewelry leads to amplified
levels of plaque, caries, recession with or without gingival inflammation, periodontal
disease that may be localized to the area of piercing. The other problems associated
with oral piercing are reduced articulation, infection with pain, tooth fractures,
allergy to the metals used, metal hypersensitivity reactions, formation of scar, speech
impediment, Ludwig's angina, and associated nerve damage. Pigmented iatrogenic lesion
such as “amalgam tattoo” and exogenic lesion such as “graphite tattoo” are also not
uncommon among people.[28]
Table 2
Various oral jewelry noted in the oral cavity
|
Design
|
Forensic Value
|
|
Tooth jewel
|
Resins are used in dentistry to attach microjewels on the facial surface of teeth
as these have resistance toward high temperatures and water environmental conditions
|
|
Hallmarked implant
|
Ceramics or various metal implants have desirable characteristics features such as
resistance to corrosion and temperature similar to stainless steel
|
|
Hallmarked pin/post
|
Seen within the tooth structure it has resistance to both water and heat and these
pins are hallmarked the same way as the implants
|
|
Tooth or crown with tattoo
|
Has resistance to both temperature and water as these are minute jewels placed on
ceramics
|
|
Removable tooth ring
|
Ceramics, stainless, or sterling steel are made used in the removable form because
of its heat and corrosion resistance properties
|
|
Fixed tooth ring
|
Ceramics, stainless, or sterling steel are placed on the anatomical crown. These are
used because of the protective nature of oral cavity and because of its heat and corrosion
resistance properties
|
Physical Abuse
Physical abuse usually presents as bruising, abrasion, laceration, hematoma, or ecchymosis.
In the orofacial region, it may be seen in the palate, gingiva, or dentition. Lacerations
in the labial or lingual frenum are hallmark signs of physical abuse in minors. They
may be a result of forced feeding or any other aggressive activity. Teeth fracture,
avulsions, dislocations may be seen secondary to trauma. Discolored teeth may be seen
in cases where the teeth have become nonvital due to previous trauma. Maxillary and
mandibular bone fractures may also be seen in severe forms of physical abuse. The
paraoral structures should also be examined for suspected injuries. Periorbital hematoma,
contusions, ptosis, dislocated lens, retinal or subconjunctival hemorrhage, nasal
fracture, rupture of the tympanic membrane, and auricular hematomas are other commonly
noted signs of physical abuse in the orofacial region.[7]
Sexual Abuse
Erythema, ulcer, or lacerations are seen on the lips, tongue, and palate in cases
of sexually abused victims. Bite marks are also common findings in sexually abused
victims.[7] In case of forced oral sex, petechiae may be noted at the junction of hard and soft
palate or on the floor of the mouth. In case of a violent blow to the upper lip, a
tear of the superior labial frenum is a pathognomonic sign of abuse in nonambulatory
children.[29]
Vesicles with purulent discharge or ulcers and condylomatous lesions of nose, lip,
tongue, palate, or pharynx may be seen in cases of infections caused due to sexually
transmitted diseases (STD). In suspected cases of STD, comprehensive examination and
laboratory culture for syphilis, gonorrhea, human immunodeficiency virus, chlamydia,
and human papillomavirus are recommended in accordance with the “guidelines for the
evaluation of sexual abuse of children” (American Academy of Pediatrics).[7]
Dental Neglect
Dental neglect as defined by the American Academy of Pediatrics Dentistry is “willful
failure of parent or guardian to seek and follow the treatment necessary to ensure
a level of oral health essential for adequate function and freedom from pain and infection.”
Easily identifiable oral and paraoral signs of neglect include early childhood caries,
improper oral hygiene, halitosis, untreated rapidly progressive dental caries, abscess,
periodontal disease, recurrent odontogenic infections, aphthous lesions that occur
as a consequence of a deficient nutritional status. Dentists can carry out an early
diagnosis of dental neglect from the parent as an absent or uncertain anamnestic to
concrete questions regarding child’s physical and psychological growth stages.[7]
Three-Dimensional Printing—An Aid to Forensics
Three-Dimensional Printing—An Aid to Forensics
The invention rapid prototyping, popularly referred to as 3D printing, includes both
prototyping and manufacturing process in every field including medicine and dentistry.
Reconstruction of face, identification and reconstruction of weaponries used, and
identification of fracture pattern are some of the innumerable applications of 3D
printing. 3D printing is positively employed to unravel several unsolved cold cases.
Recreation of major bones including the skull is made possible with the postmortem
scans of victims and the reconstruction of such detailed anatomic structures noninvasively
is one among the major advantages of 3D printing that is utilized primarily to solve
cases.[30]
Conclusion
The process of recognizing a large number of victims of natural disasters and detection
for the prosecution of criminal activity is complicated. For this purpose, forensic
profession employs science and technology to ensure delivery of justice, necessitating
the coordinated efforts of a multidisciplinary team that covers all dental specialties.
An unwavering effort must be made for the uptake of international guidelines and codes
to computerize all data using readily available technologies.
