Faculty of Health Sciences
School of Dentistry
Department of Oral Pathology and Oral Biology
Selected Highlights from Research Findings
South Africa’s high crime statistics have regularly featured in the news recently, with a very high incidence of murder, rape and child abuse. Research has indicated that as many as 28% of female rape victims are bitten during the course of the attack, and that biting is common during all violent crimes.
Bite mark analysis can be instrumental in identifying the perpetrators of these violent crimes. Part of the recognised protocol for investigating such cases therefore involves taking impressions of the bite marks for macroscopic and microscopic analysis.
Since bite mark impressions form an integral link in the chain of evidence, it is vital that the materials used to take such impressions maintain their dimensional stability over time.
However, research conducted by Prof Herman Bernitz at the Department of Oral Pathology and Oral Biology has indicated that the impression material most commonly used in forensic dentistry does not meet this criterion.
When dentists are asked to take impressions of bite marks, they tend to use the material they already have in stock. Impregum is one of the most popular impressions materials used in dentistry, as it is highly suited to crown and bridgework.
This material is therefore also often used to take impressions of bite marks in skin– although the product was not designed with this primary use in mind.
Bernitz and his colleagues garnered clear evidence in the field and research laboratory that the polyether impression material, Impregum was unstable after coming in contact with skin: such impressions tend to alter their physical properties with time, becoming sticky and unusable as evidence.
The results of their study, which has generated a certain amount of controversy, led to the recommendation that Impregum should not be used in applications where the impression material will come into contact with skin, especially where such impressions will need to be stored for any length of time.
The recommendation is that it not be used in forensic cases to take impressions of skin for the purpose of collecting bite mark evidence
Contact person: Prof H Bernitz.
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