Skeleton Keys to Identifying Human Remains-

-Forensic Odontology-

By Honey Morales

Crime shows Serial Killer Documentaries and law enforcement dramas dominate the airwaves. Typically, these are inquiries into homicides and the disappearances of people. As a result, I, a dental hygienist, found myself wondering if it were indeed possible to recognize a person by their unique set of teeth.

The DNA from the pulp chamber can be extracted and crossmatched to identify a victim, one of several methods of using teeth for identification. Simple dental records are an alternative. A match can be made, for instance, if it is known that tooth #30 is a MOD amalgam, that tooth #14 is a MO composite, and that tooth #2 is crowned with PFM (Porcelain fused to metal crowns) . It is possible to identify a body by matching dental records even if the skin and other remains are beyond recognition. A person's unique bite mark, created when their teeth meet or occlude, is another reliable means of identification. A bite mark left by a criminal has led to the capture of the perpetrator.

Ameloglyphics, also known as enamel rod patterns, are a modern method of identifying individuals through their teeth. Teeth, as we all know from our dental anatomy classes, are among the strongest in the body. The enamel and dentin of a tooth are its toughest parts and may resist decay. Like fingerprints, the pattern of your enamel rods is unique to you. When compared to fingerprints, the enamel rod patterns on teeth are more durable and cannot be altered through heat or mechanical means. The unique characteristics of a tooth, the enamel rod patterns, are fixed once the tooth has formed and erupted. The growth of enamel rods takes on a structure resembling fingerprints. Near the tooth's cusp, the enamel rods begin to slant away from the tooth's body, having been mostly horizontal in the lower part of the tooth.

The tooth needs to be acid-etched in order to get a "print" of the enamel on a rod. The result is a smoother, more uniform tooth. Rubber-based materials and cellulose acetate paper are two examples of straightforward impression materials. Then, this print's record needs to be kept someplace dry, clean, and secure. It's possible that one day soon we'll be able to scan a person's teeth to create a record that can be used in biometric verification. The development and testing of software to determine whether or not it can reliably identify a person from their biometric tooth print is still in its infancy.

Tooth prints could also be used in situations where workers are particularly vulnerable to harm on the job. Military personnel, law enforcement officers, SAR members, and paramedics all fit this description. In the event of an emergency, a person's tooth print could prove useful in these professions. A tooth print may need to be updated every few years if it is used as part of a person's permanent record because teeth wear down over time from occlusion. The amelogenin gene in teeth can be used for identification as well. The victim's gender can be determined by extracting this gene from the tooth pulp and analyzing it with a polymerase chain reaction. Gender in living victims can be accurately determined through blood testing, but for the deceased, DNA can be accessed through their teeth and bones. Fifty teeth that had been deemed nonviable for 1-3 months were used in the study, which took place in India. In each of the 50 cases, the gender of the tooth's owner was correctly determined.

The teeth were heated to very high temperatures as well. Because of their larger pulps, molars and premolars were the teeth of choice for this procedure. In addition, it was discovered that the tip of these teeth was the most reliable and preferred area. The mandibular bone has proven to be a reliable source of DNA in cases where teeth are unavailable due to decay, premature loss, or larger restorations. The mandible is a relatively small and easily extracted bone that can be used for age and sex determinations.

Over the past few years, radiographic tooth and jaw identification has grown in popularity. After a person dies, their radiographs are comparable to those taken of them while they were still alive. In 42% of these cases, victims have been located using this technique. Although chests are most easily distinguished in radiographic comparisons, skulls are identified correctly in 20% of instances. Eleven distinguishing features can be used in conjunction with dental radiographs to positively identify victims. These features include missing/impacted/retained primary teeth, "hidden restorations" like implants, bone patterns, and anatomical landmarks. Sometimes this is not a reliable identification tool because dental restorations can leave artifacts on radiographs.

It has also been discovered that ultraviolet lights help distinguish between natural tooth structure and restorations in severely decomposed bodies. The mastoid process and mandibular ramus are useful indicators of a person's sex. Finally, a victim's age can be determined by looking at their tooth eruption. In fact, this is more precise than skeletal age estimation. All primary teeth and some permanent teeth are formed in utero, making prenatal evaluations more reliable because they are immune to the effects of diet and lifestyle.