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Guided By :Dr. Vishwa Prakash Shetty
Dr. Aparna Dave
Dr. Manpreet Arora
Dr. Bhuvnesh Yadav
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Forensic is derived from the Latin word forum,which means court of law. Odontology
literally implies the study of teeth.
Forensic odontology, therefore, has been
defined by the Fdration DentaireInternational (FDI) as that branch of dentistrywhich, in the interest of justice, deals with theproper handling and examination of dental
evidence, and with the proper evaluation andpresentation of dental findings.
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Mass disasters
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Why dentists
Deceased individuals requiring identification
who sustained significant facial trauma
precludes visual identification
BECAUSE
Soft tissues does not resist the ravages of time
and environment.
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The resistance nature of dental tissues to
environmental assaults, such as incineration,
immersion, trauma, mutilation and
decomposition make teeth represent an
excellent source of DNA material. When
conventional dental identification methods
fail, this biological material can provide thenecessary link to prove identity through DNA
profiling.
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SAMPLE COLLECTION
DNA evidence collection must be performedcarefully.
-avoid contaminating the area where DNA might
be present by not touching it with your barehands, or sneezing and coughing over theevidence.
-use clean latex gloves for collecting each item of
evidence. Gloves should be changed betweenhandling of different items of evidence.
-each item must be packed separately.
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-samples should be packed in paper envelopes
or paper bags after drying.
-all types of stains must be thoroughly air
dried prior to sealing the package.
-stains on immovable surfaces such as table or
floor may be transferred with sterile cotton
swabs and distilled water.
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TECHNIQUES EMPLOYED FOR
OBTAINING DENTAL DNA
Crush entire tooth.
Conventional endodontic access.
Horizontal section of tooth with partialextirpation of coronal and radicular half of
tooth.
Horizontal section of tooth with aggressive
pulpectomy and crushing of radicular half of
tooth.
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The yield of DNA per gram of tooth powder is
approx 18.4 g.
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SALIVA
The objective of using saliva as a source is to
analyze DNA from desquamated epithelial
cells.
Salivary deposits left behind as a result of
bites can also be a potential source of DNA of
a suspect.
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A reliable method for saliva sampling from
bite-mark sites in skin is the double swabbing
techniques.
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The swabs are completely air dried and
transferred to micro centrifuge tubes.
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Saliva may also be isolated from various
sources in the crime scene, for example,
postage stamps and envelopes, glasses,
cigarettes, straws, food and chewing gum,toothbrushes and dental floss, and dental
impressions.
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Dried saliva may be difficult to detect, for
confirmation
Amylase assay
Fluorescent spectroscopy
laser
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The saliva thus collected can be dabbed onto
specialized cards.
The FTA cards (Flinders Technology Associates)
are chemically treated filter papers designed
for the collection and room temperature
storage of biologic samples for molecular
analyses.
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Blood
Blood stains are also obtained using a swab an
dabbed on to the FTA paper.
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Reference Samples
from suspects or convicted felons and
family reference samples are used in missing
persons investigations, paternity testing and
mass disaster victim identifications.
Buccal cell collection
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Storage
Most biological evidence is best preserved
when stored dry and cold.
Inside the laboratory, DNA samples are either
stored in a refrigerator at 4C or a freezer at -
20C. For long periods of time, extracted DNA
samples may even be stored at -70C.
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DNA Amplification
The polymerase chain reaction (PCR) is a
biochemical technology in molecular biology
to amplify a single or a few copies of a piece of
DNA across several orders of magnitude,generating thousands to millions of copies of a
particular DNA sequence.
Developed in 1983 by Kary Mullis.
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The final DNA concentration should be in the
range of 0.05-0.125ng/L, so that it will be
added to the PCR reaction in a volume of 10
L.
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PCR Thermocycler
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Polymerase Chain Reaction
7
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Gel electrophoresis
The different sized fragments are separated by a process
called gel electrophoresis
The separation takes place in a sheet of a firm but
jelly-like substance (a gel)
Samples of the DNA extracts are placed in shallow
cavities (wells) cut into one end of the gel
A voltage is applied to opposite ends of the gel
DNA has a negative charge and moves slowly towardsthe positive end
The shorter fragments travel through the gel faster than the
longer fragmentsGel electrophoresis
7
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12
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Appearance of separated fragments on gel
These bands will
contain the shorter
DNA fragments
These bands willcontain the longer
DNA fragments
starting positions Appearance of bands
12
Prof. E. Wood Prof. E.J.Wood
V S S S S DNA profiles 16
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V S S1 S2 S3
V Victim
S Sample from crime scene
S1 Suspect 1
S2 Suspect 2
S3 Suspect 3
More than 20 fragmentsfrom Suspect 1 match those
taken from the crime scene
DNA profiles 16
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Genetic Analyser
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E i i i
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Estimating size
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Paternity test 19
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position ofrestriction
fragment
part of DNA strand
mother father
Child will receive one copy of the restriction fragment from the
mother and one from the father. It could be any one of these
combinations
child
Paternity test 19
20
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Starting position of sample
1 2 3 4
Genetic fingerprint of
1 mother
2 child
3 possible father A
4 possible fatherB
There is a match between one ofthe childs restriction fragments
and one of the mothers.
There is also a match between the
childs other fragment and one from
possible father A.
Neither of the childs restriction
fragments match those of possible
father B
Paternity test
20
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Whenever dental professionals are required or
requested to provide such samples,
knowledge of sampling and storage for the
optimization of the DNA analysis procedurecan greatly enhance the efficiency of the
investigation. The dental expert needs to be
aware of relevant legal and ethical issues andoperate within the ambit of the law.
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ss
Thank you
THANK YOU
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