الفهرس 
FIRE RELATED DEATHSOnly 14 pages are availabe for public view
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Abstract
I
dentification of severely burnt bodies is a forensic challenge. A variety of events can lead to burned skeletal remains such as aircraft accidents, bombing, explosions and earthquakes. Homicidal, suicidal and accidental deaths all can involve the use of fire with variable results on human remains. Fire can be employed in an attempt to destroy forensic evidence in criminal cases, often to attempt to prevent identification and recovery.
The degree of destruction in burned bodies depend on many factors such as the temperature to which the body was exposed, the time for which it is applied, the kind of transmission of heat to the body and other prevailing conditions.
In burnt bodies, burning of the face and skull makes the visual identification of victims impossible and burning of hands and feet makes the conventional fingerprinting a hard task. DNA profiling is recognized as one of the possible key modes of identification in such cases.
There are two main cellular locations for DNA, and both can be analyzed for profiling purposes, nuclear DNA which is found in the nucleus of each nucleated cell in the human body and represents a DNA source for most forensic applications, and mitochondrial DNA which resides within mitochondria in the cytosol of the cell.
Teeth are expected to be an excellent source of DNA. The interest of using dental tissues as a DNA source is attributed to the resistance of these tissues against physical or chemical insults.
Pulp tissue is commonly used for the purpose of extracting DNA for identification since it is likely not to be contaminated by non-human DNA and is protected from external environment by dentin and by the highly mineralized enamel which is also the hardest structure of the human body.
The present study aimed to assess integrity of the DNA recovered from isolated human teeth after being exposed to different high grades of temperatures (100ºC, 300ºC and 500ºC) as a tool for forensic identification.
This study was performed on 30 human teeth extracted for medical causes in Ain shams university dental clinic, the 30 teeth were divided into three groups, each group consisted of 10 teeth exposed to 100 ºC, 300 ºC and 500 ºC for 15 minutes respectively. Each tooth was opened by low speed round burr contra. Control sample was taken from each tooth before exposure to high temperature then teeth were exposed to the required temperature in an electrical furnace and another samples of teeth pulp were taken to test DNA retrieval.
DNA extraction from teeth pulp was done by commercial Quiagen kit, followed by PCR study for detection of the following loci (TH01, D13S317, D7S820, D18S51, D21S11, CSF1PO) followed by gel electrophoresis for visualization of DNA bands.
Real time PCR was done for detection of Amelogenin for determination of sex.
Results of our study showed that all the tested loci were detected on exposure to 100 ºC and there was no significant difference from control samples, while on exposure to 300ºC there were dropped out loci with the most stable locus was TH01. They were detected only in 20% of the samples as regard loci (D13S317, D18S51, D21S11) and in 30% of the samples as regard loci (D7S820, CSF1PO) while TH01 was detected in 80% of the samples.
On exposure to 500ºC there was complete loss of all the tested loci as nothing could be detected at this temperature.
Similar results were obtained in sex detection by Amelogenin, which was detected in all samples exposed to 100ºC while it was only retrieved from 60% of samples exposed to 300ºC and not detected at all in any of the samples exposed to 500 ºC.
Other studies showed similar results as they didn’t obtain any STR loci in exposure to 500ºC and some studies showed that mtDNA was more stable in high temperatures.
So we concluded that high temperature leads to degradation of DNA, Complete DNA profile can be obtained from teeth pulp on exposure to 100ºC, while partial DNA profile can be obtained on exposure to 300ºC and no DNA profile can be obtained on exposure to 500ºC. Amelogenin is a good predictor of sex till 300ºC while it is completely lost at 500ºC. There was no significant difference detected between molar and premolar teeth or between male and female on exposure to high grades of temperatures (100ºC, 300ºC and 500ºC).
More studies are recommended on wide scale teeth samples to verify our results and on other STRs loci to detect the most stable loci, moreover studies should be done to find other methods of identification in high temperatures when DNA is completely lost.