forensic odontology
TRANSCRIPT
Forensic Odontology
Definition
Defined by the Fédération Dentaire International (FDI)
That branch of dentistry which deals which, in the interest of justice, deals with the proper handling and examination of dental evidence, and with the proper evaluation and presentation of dental findings.
Deals with identification, based on recognition of unique features present in an individual’s dental structure
Role in identification in man made or normal disasters-events that result in multiple fatalities
Dental evidence can be crucial in crime investigation
Relies on sound knowledge of the teeth and jaw, possessed by dentists and incorporates dental anatomy, histology, radiography, pathology, dental materials and developmental anomalies
Forensic odontologists devel into Identifying unknown human remains through
dental records, assisting the location of a mass disaster
Eliciting the ethnicity
Determining the gender
Age estimation
Recognition and analysis of bite marks
Presenting evidence in court as an expert witness
Personal identification Identification is the establishment of a
person’s individuality
‘The characteristics by which a person may be recognized’
Tradition methods: visually recognizing the body, personal property
Physical features: inherited or acquired
Inherited features: ethnic characteristic
Acquired features: surgical scar, previous fractures, dental restorations
Prone to change over time
Dental hard tissue: strongest structures Resistant to post-mortem decomposition Most dental materials are also resistant
Basis for dental identification Human dentition is never the same in any
two individuals, ‘uniqueness’
Restorations
Extracted, missing Combination of 16 missing teeth can
produce is approximately 600 million
Four missing & four filled teeth in mouth combined can produce more than 700 million combinations
There are 1.8 * 10 to power 19 possible combinations of 32 teeth being intact, decayed, missing or filled
Dental identity: “the total of all characteristics of the teeth and their associated structures which, while not individually unique, when considered together provide a unique totality”
Dental identification procedures
Two forms are there:
Comparative identification: attempts conclusive identification by comparing the dead individual’s teeth with presumed dental records of the individual
Reconstructive identification: elicit the ethnicity or ‘race’, gender, age, and occupation of the dead individual
Comparative dental identification
Convectional method
Four steps: Oral autopsy Obtaining dental records Comparing post- and ante-mortem
dental data Writing a report and drawing
conclusion
Oral autopsy Necropsy or post-mortem
Examination of the deceased, usually with dissection to expose the organ, to determine the cause of death
Critical examination of the external features
Photographs, radiographs, fingerprints, fingernail scraping, hair sample, obtained according to the requirement.
Oral examination Essential part
Rigor-mortis: render jaws rigid Use of mouth-gags Intraoral myotomy is essential
Teeth need to be reinforced prior to examination
Access for radiography can be obtained by removing the tongue and contents of the floor of the mouth in a ‘tunneling’ fashion from beneath the chin
Examination of : Soft tissue injuries Fractures Presence of foreign bodies
Samples of hard and soft tissues may be obtained
All information, entered onto ‘Interpol post-mortem form’
Color-coded in pink
Obtaining dental records
From the treating dentist, specialist or hospital records
In the form of dental charts, radiographs, casts and/or photographs
Transcribed onto ‘Interpol ante-mortem form’
Color-coded in yellow
Comparing Post- and Ante-mortem dental records
Data can be compared
Tooth morphology and associated bony structures, pathology & dental restorations
Individual with multiple dental treatment and unusual features has a better likelihood of being identified
Writing a report and drawing conclusions
Detailed report and factual conclusion, based on the comparison, must be clearly stated
In fingerprinting, differences in the ante-and post-mortem data rule out identification
This concept does not apply to dental identification, as long as the inconsistencies are explainable
Range of conclusions
Confirm Identification: the ante- & post-mortem data match each other
‘beyond reasonable doubt’ Usually includes radiographic support
Probable Identification: data is consistent but a lack of quality
One cannot confirm identity No radiographic support
Possible identification: explainable differences exist between the ante- & post-mortem data
Insufficient information: the available ante- or post-mortem information is minimal or insufficient
Excluded identification: ante- & post-mortem data are clearly inconsistent
Indicates mismatch
Identification in disasters Disasters: natural, accidental, man made events
Result in multiple human fatalities
Severe mutilations
Magnitude of the event is far greater
Involves comparing hundreds, sometimes thousands, of ante & post-mortem data
Bodies may be incinerated or commingled
Jurisdictional and political issue that need to be addressed
Dental section
Part of a team of identification specialists
Most disaster identifications have a dental section
Inclusion of different specialists and dental auxiliaries
Tasks range from talking radiographs to performing clerical duties
Division of dental section into 3 subsections:
Post-mortem unit
Anti-mortem unit
Dental comparison & identification unit
Post-mortem unit
Dentists are more likely to recognize fragmented and burned teeth
Sketch should be made of the scene
The location at which a body is recovered is noted
Preliminary examination of the mouth
Dental examination is usually done after most other procedures such as
Photography Fingerprinting Medical autopsy
Portable dental radiography apparatus
Teeth and jaw specimens may be removed
Labeled to prevent a ‘ mix-up’
Ante-mortem unit Collect as much information as possible in
the shortest period of time
Written dental records, radiographs, study models
Personnel should be capable of reading and interpreting all dental records provided
All information transferred onto the standard Interpol ante-mortem form
Dental comparison and identification unit
Comparison and confirmation of identification
All ante-mortem data may or may not be available
Done manually or by computer aid
Data can be sorted by gender, age, presence or absence of restoration etc…
Fragmentary remains will need to be crosschecked with individual bodies
When matched, all set of documents relating to dental features are attached to the relevant sets of documents for the rest of the bodies
Computer software programs has also been developed
Final identification should always be done by the dentist manually, based on personal evaluation of evidence
Success depends on the co-operation between different identification teams
Identification from dental data
Teeth are an excellent source of DNA
Polymerase chain reaction (PCR), allows amplification of seven highly degraded DNA
Sample: hair from hairbrush, epithelium from toothbrush or a biopsy specimen
Advantage: if a decedent’s ante-mortem sample is unavailable, the DNA pattern may be compared to a parent or to a sibling
Extraction of dental DNA Pulpal tissue is the best source
Cryogenic grinding
DNA can be obtained from intact, carious, as well as root-filled teeth
Dentine and cementum may be equally viable
Particular significance in skeletal remains
Major drawback of cryogenic grinding:
Tooth needs to be completely crushed
Less destructive method:
Drilling of the root canal
Scraping the pulp area with notched medical needle
Subsequent flushing of the tissue debris
Types of DNA Two types: Genomic or nuclear DNA: In the nucleus of the cell
Mitochondrial DNA: A high copy number of mtDNA
Exclusively inherited from mother
An identical mtDNA pattern is observed among siblings, their mother and many maternal relatives
Used to establish identity in cases where there is a gap of several generations
The palatal rugae in identification
The rugae pattern on the deceased’s maxilla or maxillary denture may be compared to old dentures
They don't change shape with age and reappear after trauma or surgical procedures
Classification of palatal rugae
Primary rugae ( > 5 mm)
Secondary rugae ( 3-5 mm)
Fragmentary rugae (2-3 mm)
[ Rugae <2mm is not taken into consideration ]
Analysis of rugae pattern
Traced rugae pattern on to clear acetate
Superimposed these tracing on photographs of plaster models
Computer software program, ‘RUG FP-ID Match’
Makes use of the principle commonly employed in fingerprint analysis
Dental profiling
Profiling includes:
Extracting a triad of information
The decedent’s ethnic origin, gender, and age
Identifying ethnic origin from teeth
Humans are a diverse species
Results of genetic influences, as well as environmental factors
Three ‘races’ : Caucasoid, Mongoloid, Negroid
Possible to identify an individual’s ethnic origin based purely on one’s dentition
Genetic and environmental influences on teeth
Dental features have evolved over time as a result of genetic and environmental forces
Dental features are a combination of hereditary and environmental factors to which a person is exposed
Those dental features that have a stronger genetic and weak environmental influences are useful
Dental features:
Metric Features(tooth size): based on measurements
Non-metric (tooth shape): based on presence and absence of a particular feature
Sex determination
Based on data from :
Morphology of skull and mandible
Metric features
DNA analyses of teeth
Sexing from craniofacial morphology and dimensions
Use of morphologic features of the skull and mandible
Not reliable until well after puberty
Use of multiple features
Their application may need to be confined to young adults and the middle-aged
Measurements of the skull using lateral cephlometric tracings
Variable such as:
Length of the cranial base
Mastoid height and width
Total face height
Maximum length of the skull, male skull is larger
Numerous variables on dry skull specimens
Sex differences in tooth size Differentiating sex by measuring their mesiodistal and
buccolingual dimensions
Significant differences between male and female permanent and deciduous tooth crown dimension
Such measurements are: population specific Do no apply to the world at large
Canine consistently show the maximum sex difference
Premolars, first and second molars as well as maxillary incisors are also known to have significant differences
Dental index
‘Incisor index’, calculated by:
Ii = [MDI² / MDI¹] * 100
Where MDI² is the maximum mesiodistal diameter of the maxillary lateral incisors
MDI¹ is the maximum mesiodistal diameter of the central incisors
Index is higher in males
‘Mandibular canine index’, calculated as:
(Mean m-d canine dimension in females + S.D.)
+ Mean m-d canine dimension in males – S.D. 2 Value: 7.1mm, is the maximum possible
mesiodistal dimension of mandibular canine in females
Dimension is greater in males Success rate is 89% Odontometric difference, explained as a
result of greater genetic expression in males
Sex determination by DNA analysis
Sex can be determined with very minute quantities of DNA
“Amelogenin”
The AMEL gene, located on the X- and Y-chromosomes
Females (XX) have two identical AMEL genes
Males (XY) have two non-identical genes
Dental age estimation methods
Age estimation using dentition, grouped in 3 phases
1. Ageing in prenatal, neonatal and early postnatal
2. Age estimation in children and adolescents
3. Age estimation in adults
Age estimation in prenatal, neonatal & early postnatal child
Primary tooth germ begins to form at seven weeks in utero (IU)
Enamel formation of all deciduous teeth is usually completed by the first year
Among the permanent, 1st molar show germ formation first at about 3.5-4 months IU
Age estimation can be very accurate
Use of histologic techniques
Neonatal lines
Neonatal line may take up to three weeks after birth to form
It indicates a live birth
Age estimation in children and adolescents
Tooth emergence or ‘eruption’
Tooth calcification
Visual assessment of teeth present in the mouth
Deciduous teeth, their emergence is under genetic control, relatively regular
Emergence pattern of permanent teeth are under the influence of the intraoral environment
Affected by infections
Arch space
Premature tooth loss
Evaluation of radiographs to assess tooth calcification is a much better alternative
Number of teeth passing through various stages of calcification, are available
Better indication of ages in first two decades
Schour & Massler’s method
Described 20 chronological stages of tooth development startinh from four months IU until 21 years
Based on histologic sections
Direct comparisons with radiographs
Dental development of males and females were combined and each stage included the amount of age variation
Demirjian’s Meathod Age estimation method that made use of a
scoring system
The development of seven mandibular teeth on the left side was divided into eight stages each
Stages named as ‘A’ to ‘H’
While third molars are not used
Each tooth is assigned a ‘maturity score’
The maturity score assigned is added and a total maturity score is obtained
Total maturity score: plotted on a chronologic ‘ age conversion table’
Third molar in age estimation
Accuracy in age estimation is questionable due to:
Their great variation in genesis Position Morphology Time of formation
When all four third molars have completely calcified, the chances of the individual being 18 years old is:
96.3% for males 95.1% for females
When all four third molars are unavailable for age estimation:
Only one or two may be in hand
In such lower third molars are best predictors
Age estimation in adults
Gustafson’s method
Age estimation based on:
Morphological and
Histological changes of the teeth
This assessed regressive changes as:
Amount of occlusal attrition (A)
Coronal secondary dentine deposition (S)
Loss of periodontal attachment (P)
Cementum apposition at the root apex (C)
Root resorption at the apex (R)
Dentine translucency (T)
Different scoring ranging from 0-3 were assigned:
Adding the allotted score for each variable, a total score was obtained
Age estimation using the formula, Age = 11.43 + 4.56X
Maples & Rice proposed Age = 13.45 + 4.56X
Age estimation from incremental lines of cementum
Age estimation from acellular cementum incremental lines
Made use of mineralized, unstained cross-section of teeth
Preferably mandibular central incisors and third molars
Accuracy of within two or three years of the acute chronologic age
Major disadvantage: necessity to extract and/or section the teeth
Report and conclusion of age estimation
Wordings reveal the underlying concepts of age estimation
The materials that were obtained for age estimation
Method(s) used
It is important to address the applicability of the method(s) to population on which it was used
Dental age cannot be expressed precisely, but at best, within an age range
Bite marks
Defined by MacDonalds “ A mark caused by the teeth either alone or in combination with other mouth parts”
Caused by humans or animals
They may be on tissue, food items, or other objects
Primitive type of assaults, teeth used as weapon
Outline of human bite marks are: Broad U-shaped Sometimes circular or oval
Bite marks of animals are: Narrow in anterior aspect V-shaped Elongated
Difference in the morphology of the teeth
Human bite marks have: Broad central Relatively narrow lateral incisors Blunt
Bite by animals exhibit: Broad laterals Narrow centrals Sharper and deeper canines marks
Human bite marks are present in cases of:
Sexual assault Fight and violence Child abuse Theft
Size, shape and pattern of the incisal or biting edges of upper and lower anterior teeth to be specified to an individual
Depict the ‘unique’ pattern of a biter’s teeth
Classification of bite marks
Cameron and Sims Classification
Agents Human Animal
Material Skin, body tissue Food stuff Other material
MacDonald’s Classification
Tooth pressure marks “direct application of pressure by teeth” By the incisal or occlusal surface of teeth
Tongue pressure marks When sufficient amount of tissue is taken
into the mouth, the tongue presses it against rigid areas such as the lingual surface of teeth and palatal rugae
Combination of sucking & tongue thrusting
Tooth scrape marks Scraping of teeth across the bitten
material Caused by anterior teeth Present as scratches or superficial
abrasions
Webster’s Classification Bite marks in food stuff
Type I : food item fractured readily Limited depth of tooth penetration e.g. : hard chocolate
Type II : fracture of fragment of food item
Considerable penetration of teeth e.g. : bite marks in apple & other firm
fruits
Type III : complete or near complete penetration of food item
With slide marks e.g. cheese
Bite mark appearance Type of injury: compression of the skin surface
due to tooth pressure during a bite causes indentations initially
Indentations soon disappears
Brief period of edema over the bite area
Once the edema subsides, subcutaneous bleeding is apparent
Contusion or bruises
Reddish/purplish discoloration on the skin surface
When the intensity of the bite mark is great, there may be a break in the integrity of skin surface
Resulting in lacerations
Most extreme form: avulsion, where part of the tissue is bitten off
Identifying the injury as a bite mark: human bite marks can be identified as:
Gross features: A circular or elliptical mark Found on skin with central area of
ecchymosis Circular/elliptical mark is caused by the
upper and lower arches Ecchymosis due to sucking action or
negative pressure
Class features: Differential between different types of teeth Incisors produce rectangular marks Canines are triangular or rectangular
Individual features Characteristics such as fractures Rotations
Site of bite mark Can be found on any parts of the body
Bite mark investigation
Preliminary questions
Bite mark evidence collection from the victim
Should be collected when it is first presented and observed
Primary concern is patient Great potential for infection Protocol
Visual examination Type of injury Contour, texture, elasticity of the bite site Physical appearance Differences between upper and lower
arches, and between individual teeth If victim is dead, visual examination
should be done before autopsy
Photography Permanent record of the appearance of
bite marks
Color and black-white photographs from different angles
Orientation photography: depict the location of bite mark
Close-up photography: taken with a rigid reference scale
Placed on the same plane as the injury Entire scale and bite mark must be visible in
the photograph
Saliva swab Saliva may have WBCs and sloughed
epithelial cells
A potential source of DNA A cotton swab moistened with distilled
water should be used for swabbing If the bite has occurred through clothing,
cloth must also be swabbed for saliva
Impression When tooth indentations exist Material of choice: Vinyl polysiloxane Reinforced with dental stone, self cure
acrylic, or impression compound, to prevent against dimensional changes
Impression of the victim’s teeth should be made for suspected self-inflicted bites
Evidence collection from the suspect A signed and witnessed information consent
or a court order Infection control and asepsis Items of evidence recovered should include: Photographs of the suspect’s teeth Maxillary and mandibular impression Models poured in dental stone Bite registration in centric occlusion Saliva swab Case number, date, time, place, as well as
any witnesses involved must be recorded at every step
Bite mark analysis and comparison Consider movement on part of the victim
The flexibility of the bitten tissue
Distortion introduced during photography consider uncommon characteristics of the bite mark
Measurements obtained from the bite mark should be compared to that of the suspect’s dental model
Metric analysis, in conjunction with ‘pattern association’
Direct method of comparison:
suspect’s models were placed directly over the bite mark photograph or on the bite mark itself i.e. in situ
Incisal and occlusal edges of the suspect’s teeth were traced on clear acetate
Superimposed on life-size photographs of bite marks
Indirect method:
Computer software programs
Conclusion of bite mark analysis
Positive identification
Possible identification
Excludes identification
Lip prints Wrinkles and grooves visible on the lip as
‘sulci labiorum rubrorum’
Imprint produced by these grooves is termed ‘lip print’
Examination of it is referred to as ‘Cheiloscopy’
Grooves are heritable & individualistic
Classification, by Santos Simple wrinkles• Straight line• Curved line• Angled line• Sine-shaped line
Compound wrinkle• Bifurcated• Trifurcated• Anomalous
Pattern of grooves Type I: Clear-cut vertical groove that run across
the entire lip
Type I’: Similar to type I, but do not cover the entire lip
Type II: Branched grooves
Type III: Intersected grooves
Type IV: Reticular grooves
Type V: Grooves that cannot be morphologically differentiated
Combinations of these grooves may be found
Lips are divided into quadrants
A horizontal line dividing the upper and lower lip
A vertical line dividing right an left sides
The lip prints can be ‘lifted’ using material such as aluminium powder and magnetic powder
The vermilion border have minor salivary glands
The edges of the lips have sebaceous glands, with sweat glands in between
Secretions of oil and moisture from these enable development of ‘latent’ lip prints, analogous to latent finger prints
Disadvantage: uncertainty about the prominence of lip patterns
Major trauma of lip resulting in scarring, pathosis
Surgical treatment rendered to correct the pathosis, affects the size and shape of the lip, may alter the pattern and morphology of the grooves
Anatomic position of lip grooves on the zones of transition
Close to vermilion border- a zone is extremely mobile
Differ in appearance depending on the pressure applied and its direction
The dentist as an expert witness Forensic dentists, usually requried to provide testimony in the court of law in the capacity of an ‘expert witness’
“Expert witness are those whose training, qualifications, or experience enables them to give an opinion on a relevant matter where the ordinary person is not so enabled”
Dentist may need to testify in cases involving malpractice based on deficiency and negligence, accidents and injuries, & dental fraud.
Expert witness may appear for the prosecution or for the defense
Make bold statements while preparing reports and framing conclusions
Any change in opinion during questioning by the opposition lawyers can render the expert witness fallible
“Always present the evidence and conclusions based on facts”
Truth is paramount, and repeatable
Opinion should be presented in such a way that it is accurate and yet simple enough for the layperson to understand
Never to discuss matters pertaining to a case with anybody as long as the case is under trail
The expert witness in particular and the forensic dentist in general, must be:
Professional, Unbiased Ethical Truthful
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