If a body is examined and there are no immediate clues as to who this person might be, our first step at the Medical Examiner’s Office is to do a complete dental examination and xray of every tooth. It basically consists of a similar exam you are getting from your family dentist. Clinical notations are made if there are signs of malocclusion (incorrect fitting of the lower jaw to the upper jaw), unusual shading of the teeth or gums, or any other clinical notes that might describe identifiable characteristics. Detection of periodontal disease might be another example of information that could be obtained from the handwritten clinical notes.
Considerable time was spent in the last blog about the differences in how different fillings look on xray. Some are white or radiopaque while others are radiolucent or dark. This could easily mislead an untrained eye. Today’s emphasis deals with the presence or absence of a particular tooth. We will illustrate these points with some practical examples.
There are 32 permanent human teeth, including wisdom teeth or third molars. They usually erupt into the mouth from ages 6-21. There are twenty baby or primary teeth. They arrival usually begins around 6 months old and is completed by age 2. While a child has half permanent teeth and half baby teeth, we refer to that as ‘mixed dentition’.
If a body presents with a silver filling on the ‘occlusal’ or biting edge surface of #’s 2,3,14, and 15, we refer to these items as identifiable ‘markers’. That means that they have potential of being used for comparative purposes. If the xrays or records show that those same four teeth on a known individual have the same size/type filling, then that would be of significance. BUT, what if…….this same body presents with the above described fillings plus the fact that all four wisdom teeth (we would number those as 1,16,17, and 32) were missing.
You study the xrays of the known individual, who is missing, and you notice that even though all the fillings match, this patient has 4 wisdom teeth on the xray. What does that tell us?
NOTHING! Did you get it right? How come, you say? Well, those wisdom teeth could have been extracted AFTER the xrays were taken. That is what we call an explainable discrepancy.
How about this one, though -what if the body presents with all their wisdom teeth present. Now, we go to compare those wisdom teeth with the xrays supplied by the police. Those xrays show NO wisdom teeth. What conclusion can you draw? This cannot be the person in question. This is called an inexplainable discrepancy. One of these is worth more than five positive ID consistent markers.
In closing, we may conclude that baby teeth do have other teeth come in the mouth behind them. But once you get your permanent teeth, if you lose one, it’s gone forever. This fundamental principle in forensic odontology has been the singly most used principle in my 30 years of forensic identification.