Question 1

Question 1

We have all heard of how Forensic Dentistry has helped in the identification of burnt victims and also victims with bite marks. Explain more about these and describe how is Forensic Dentistry could be useful in the identification of murder victims?

1. Of burnt victims: 

Enamel can withstand temperatures of more than 1093°C¹. Although other dental treatment structures such as crowns, bridges, fillings or braces may be destroyed or damaged by the heat, they may still support forensic dentists in solving cases of burnt victims.

2. In laboratories or clinics:

Dental charts from clinics are important for identifying the victims as it is not likely for two person to have exactly the same dental treatments done on the same location of teeth respectively. The two most essential details is the type of treatment and the specific location of teeth (eg. the buccal surface of upper right first molar). Example of treatments are: amalgam restoration, extraction (missing tooth), crowning and bridgework. These information can be used to identify burnt and murdered victims where their facial structures are destroyed and unrecognizable. It is also very useful when the bite mark of victim is left on any body parts of a suspected murderer. 

example of dental chart

Dental impressions have similar function as dental charts. It is the imprint of teeth and soft tissues. It provides information of present indentations, abrasions, striations, distances between cuspids, tooth width and thickness, alignment and mouth arch. Impressions are mainly used to confirm or ruling out the identity of a suspected victim. Furthermore, it can also be used to identify the murderer if a bite mark is left on any body parts of the victim.

Reconstruction of a bitemark

example of dental impressions

3. Behind every bite mark lies an untold story:

Forensic odontologists are able to predict the crime (whether it is sexual crime, homicide, child abuse etc) based on the bite mark locations. Studies by Vale and Noguchi (1987), Pretty and Sweet (2000), and Harvey (1976) showed that bite marks on the breast areas are most common in assaulted female victims. Whereas bite marks are not uncommon to be found on arms and legs of abused children.³

Bite mark incidence by anatomical area and type of crime.

Bite depths reflect how much pressure was exerted by the assault on the victim. A 'clear' impression represents significant pressure, while an 'obvious' impression signifies medium pressure and a 'visible' impression reflects violent pressure being exerted.⁴

4. Unfolding an identity

Dental age of a victim can be determined by the number of teeth erupted for primary and mixed dentition. For permanent dentition, there are 2 major methods of analysis. Gustafson method looks at six signs of wear and Lamendin's method judges the transparency of roots. The transparency increases with ageing. The state and wear patterns of an individual's teeth can also give insight into the person's diet, personal habits such as smoking, bruxism or eating disorders. Tailors may have chipped teeth due to their habit of inserting pins or needles into their mouths.

Staining of teeth also aids in identifying of the victim. Since stains are easily recognizable, close friends or relatives of the victim may be asked into questioning to describe the victim's dentition. Smoking can cause staining of tooth surfaces and, over the long term, intrinsic staining of the tooth structure. The use of tetracycline antibiotic from children using developing teeth (aged 3-12 years old) can cause horizontal brown and grey striping of the enamel surfaces. Excessive fluoride from toothpaste and fluoride drops cause brown stains with white flecks. Older people can develop brown staining on the teeth as the enamel wears thin.

Tetracycline staining

5. Extracting DNA:

If no other sources of genetic material can be obtained from a deceased victim, DNA sample can be collected from saliva on bite marks. However, if saliva is not present, DNA can still be extracted from the dental pulp for forensic investigations.

6. Timing is vital: 

Bruising of the bite mark may start to appear from the 4th hour onward up till the 36th hour in live victims². In the event when the victim is already found dead, odontologists may have to wait for the purplish discolouration of the skin to appear in accordance with postmortem lividity. These changes may aid odontologists in estimating the time of occurrence or time of death. 

References:

1,2,4:

http://science.howstuffworks.com/forensic-dentistry.htm>  29 October 2012.1,2,4: Freeman, Shanna.  "How Forensic Dentistry Works"  20 May 2008.  HowStuffWorks.com. 

3:
Adam J. Freeman,D.D.S.; David R. Senn,D.D.S.; and Douglas M. Arendt,D.D.S., M.S. Seven Hundred Seventy Eight Bite Marks:Analysis by Anatomic Location, Victim and Biter Demographics, Type of Crime, and Legal Disposition. J Forensic Sci, Nov. 2005, Vol. 50, No. 6