The uniqueness of a
set of teeth is a powerful tool in confirming the identity
of someone unknown, especially when a lack of DNA evidence
is the case. You may be intrigued by the number of clues
an examination of teeth can provide.
Forensic
odontologists
or in other words, forensic dentists, have the
job of examining dental evidence that is left
behind after a crime has been committed. Teeth
are an excellent source of identification, as
they hard wearing and durable. With the ability
to survive fires that destroy evidence, burn human
bones to ashes and melt copper and glass, teeth
are able to withstand criminal's attempts to hide
the crimes they've committed and the evidence
held within the crime scene and dental analysis
provides a cost efficient alternative to solving
a crime.
*Worn
fillings and chipped teeth are valuable clues.
Photo courtesy of Valeri
Craigle and the Spencer
S. Eccles Health Sciences Library.
At the scene of the crime, odontologists collect
the skull or remaining teeth, which are taken back
to the forensic laboratory for the postmortem dental
investigation. X-rays are taken and if the jaw is
completely intact and the dental records used to compare
are recent, the job of proving a match is a relatively
simple one. Dentists mark on a chart the position
of missing teeth, crowns,
bridges,
fillings,
caps,
root
canals and various other treatments during
a patient's routine check-up. The task of identifying
a victim is made more difficult when the dentist records
and x-rays are out of date or when the skull is severely
damaged and has parts missing.
*To
the left is a comparison of two dental impressions,
showing the differences in dental structure between
the teeth of a 30 year old and a 5 year old. The size
of the milk teeth compared to that of the adult teeth,
and the presence of a wisdom tooth in the adult set,
are evident differences.
Photo is courtesy of Valeri
Craigle and the
Spencer S. Eccles Health
Sciences Library.
Where no
dental x-rays are found, full-face x-rays are
sometimes used as an alternative record, as the
sinuses present above the nose have a unique shape
in every person and can be used in the accurate
identification of a victim. If no dental, face
or x-ray records are present, the ability to make
decisions about the victim's identity is very
restricted, but other guidelines are useful. Some
of these guidelines include the tooth roots becoming
more transparent in older people and the stage
of development of a child's teeth can determine
their age. The teeth's pattern of wear in adult's
show the person's age, diet and the materials/dentistry
techniques used during dental treatment, which
can point out the country in which treatment was
received.
*
Two different sets of x-rays can be distinctly
different and used to prove/disprove a certain
identity. Images courtesy of www.imageafter.com.
Odontologists also play a vital role in the
study of bite marks. Human and animal teeth
both leave conspicuous marks. In the flesh,
they leave behind noticeable bruises or puncture
marks and in soft foods, such as fruit, marks
are also preserved. The distinctiveness of the
bite mark is used for the identification of
the person. For example, gaps or abnormalities
present in the teeth of a suspect are compared
with the bite mark to see whether it is logical
to say that the suspect's teeth made the bite
mark.
Bite
marks found on this apple are measured and recorded
for comparison. Photo courtesy of Dr
Berk.
To be able to
match a suspect with a bite mark, the mark is
documented using photographs and in the case of
food containing the mark, it is alcohol or other
preserving agents such as glycerol
and formaldehyde,
which are used to preserve the food. Then a record
of the suspect's teeth is acquired, where odontologists
take an impression of the teeth in silicon rubber.
The impression left in the rubber is set using
plaster to make a replica of the gums and teeth
and compared with the samples. These photos and
replicas are then compared with the crime scene
bite mark. The forensic odontologist simply gives
evidence as a witness to injuries caused by biting
and it is the method in which they choose to present
evidence in court that convinces a jury whether
a suspect guilty or innocent.
