By Shannon Rasp
Every week, millions of Americans are riveted to their television sets watching investigative crime shows. And the minute the medical examiner or detective says the words “bite mark” or “dental I.D.,” you know a dentist is about to become a crime solver.
Surprisingly, crimes often feature an oral or dental component; one study estimated that in 99 percent of all violent rapes, victims are bitten at least once by their attacker.
“A forensic dentist is called upon to help in the identification of individuals and to assist in the investigation of bite mark injuries on living or deceased individuals,” said Veronique F. Delattre, DDS, FAGD, professor in the Department of General Practice and Dental Public Health at The University of Texas Health Science Center at Houston (UTHealth) School of Dentistry. Delattre is also chief forensic consultant for the Harris County Medical Examiner’s Office.
Your ‘oral history’
A forensic dentist uses a variety of tools to identify a living individual (an unknown perpetrator of a crime, for example) or deceased person. They include:
- bite-mark identification, analysis or comparison
- lip-print identification, analysis or comparison
- the identification of dental specimens at a crime scene or elsewhere, and
- evaluation of trauma to the face and oral cavity.
In order to analyze bite marks, the forensic dentist will compare the physical characteristics of both the bite wound and the suspect’s teeth, including:
- the distance from cuspid to cuspid (the third tooth to the left and right of the midline of either jaw, also called the “canines”)
- the shape of the mouth arch
- the evidence of a tooth out of alignment
- teeth width and thickness and the spacing between teeth
- missing teeth
- the curves of biting edges
- unique dentistry
- wear patterns, such as chips or grinding.
The (not so) invisible bite
Ultraviolet light can help law enforcement when it comes to forensic dentistry, illuminating bite marks that are invisible to the naked eye. Even after a bite mark and bruise have faded, the damage to the underlying tissue remains for up to nine months. Ultraviolet light will show this tissue damage, allowing the bite mark to be seen and photographed for comparison.
Also, when someone is bitten, the bite will often retain DNA from the biter, making DNA gathering and analysis a possibility.
The Bundy case
Many crimes have been successfully prosecuted using forensic dentistry. Ted Bundy, the notorious serial killer, was convicted and executed largely because of a single bite mark he left on one of his victims. A gifted law student, Bundy defended himself during his trial and subsequent appeals. He successfully hid mountains of forensic evidence by using rental cars and living in apartments while carrying out his crimes, and wiping all crime scenes clear of fingerprints.
One thing he couldn’t wipe away, however, was a bite mark he left on one of his victims, a student at Florida State University. Dentists made a plaster mold of Bundy’s teeth and compared it to the impression left on the victim. The bite patterns matched, and Bundy was convicted. Prosecutors at the time acknowledged that their case was far from a slam-dunk; they relied on a simple bite mark to convict one of history’s most notorious murderers.
Finding lost loved ones
Criminal investigations aren’t the only things solved using forensic dentistry; sometimes mysteries are, too. After 9/11, forensic dentists across North America were asked to help identify the remains of many victims of the terrorist attacks. Most of the bodies were burned and charred beyond recognition, fragmented, or decomposing, making facial identification impossible. Teeth, however, are the hardest substance in the body, lasting much longer than bones and tissue. This characteristic makes them ideal when trying to positively identify a body.
Unlike other hard tissues, teeth are usually not vulnerable to external forces. Once a person dies, the things teeth are most vulnerable to — tooth decay and periodontal disease — no longer exist, leaving the teeth intact and stable.
Even though many of the victims of 9/11 were exposed to fire, dental clues remained. Teeth generally become brittle at 400 degrees Fahrenheit, turning ashy at about 1,200 degrees. Dental restorations, however, such as partial dentures, crowns, and bridges, survive temperatures this extreme and help make identification possible.
More unique than DNA
Identification using dental impressions is an invaluable tool. Most scientists agree that bite marks are even more unique than DNA; identical twins share the same genetic makeup, but their dental impressions will differ.
“There are 28 teeth, plus four wisdom teeth, in an adult’s dentition,” Delattre said. “Each tooth has five surfaces (occlusal, buccal, lingual, mesial, and distal), for a possible total of 160 surfaces. Each surface has its own characteristics and may have fillings, crowns, extractions, bridges, etc. In addition to the teeth we see in our mouths, the roots and bone around them are specific to each person.”
Given all of these parameters, it’s safe to say that the physical make-up of each person’s dentition is unique.
Forensic dentists are proving themselves invaluable to law enforcement through their ability to use something as seemingly simple as a person’s dentition to identify criminals and their victims. As America continues its fascination with the science of the human body, forensic dentistry will continue to make its own important contributions.
This article, which has been updated, originally appeared on HealthLEADER, an online wellness magazine produced by The University of Texas Health Science Center at Houston (UTHealth). Visit HealthLEADER for more articles on a broad array of health and wellness topics.