The Reliability of Forensic Dentistry
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In the fall of 1975, I opened a family dental practice in Hendersonville, Tennessee, just after a two year hitch in the U.S. Army Dental Corps in Ft. Polk, Louisiana. Eight years later, in the summer of 1983, I began officiating high school football in the middle Tennessee area. One of my fellow officials happened to be the current medical examiner for Davidson County. After one of our weekly meetings, he asked me if I had any interest in looking at the mouth of an unknown decedent (forensic word for ‘dead guy’) whose body had just been discovered at Riverfront Park in downtown Nashville. I said, ‘sure, why not?’
My first trip to the morgue followed the football meeting where I was exposed to what human remains look like that have been in the woods for weeks in an adjacent county in the middle of a hot and humid summer. Not a pretty sight! Not one for those who have a sensitive nose! It is an odor you will never forget. Even if you try!
That case was unusual in the fact that there were several gold fillings in the mouth of the decedent. These dental restorations are usually quite expensive, and the tattered rags the poor chap was wearing indicated he might have been a street person. That peaked my curiosity initially. The restorations appeared to be what dentists call ‘gold inlays’. To a lay person, it looked just like a shiny gold filling. This type of restoration was becoming a lost art, even back in 1983, and is rarely seen today. As the science of dental restorative materials have changed over the years, they have now been replaced mostly with porcelain type restorations since our patients now demand more cosmetic fillings today.
I remember like it was yesterday. There were eight of these beautiful gems that caught my eye. I tried to focus on the unique pattern of the fillings, hoping that would help me ignore the sights and smells of the badly decomposed remains. It didn’t work. My mentor laughed at the nausea that initially came over me, as I had to take a ‘bathroom break’ ten minutes after beginning my first oral autopsy. How embarrassing!
He gave me my first tip from his years of expertise. He gave me one of those ammonia ampules, the type that you squeeze and break, bringing out a strong odor, surely to revive anyone who might be passed out, or on the verge. By breaking the ampule and placing the contents inside our masks, it’s strong odor did help to counteract the stinch that seemed so overwhelming.
After returning to the autopsy table, the ammonia helped cut down the odor, but my eyes continued watering like crazy from the strong smell of the ammonia. Then I had to stop and blow my nose three or four times. I thought to myself, this may be the first and last time I get to be involved in the identification process. But my mentor was understanding , sympathetic and patient. He reminded me that what doesn’t kill you will make you stronger. It was a couple of years, however, before I could tackle a ‘decomp’case like this without some ammonia assistance.
Since Metro police had no local missing persons reports matching the description of the body, our process was one of record making at this time. We began by doing a complete dental charting of the conditions in the mouth. The body was bloated and had already completed its stages of decomposition that included rigor mortis, where the body had become very stiff and rigid, making opening of the jaws difficult or impossible.
Now that I’ve probably lost most of you with nausea or boredom, we’ll take the forensic process one step further. If forensic scientists are attempting to ID an unknown body, we must first have an idea of who we think it might be. This holds true with fingerprint identification or DNA comparison. The nice thing about fingerprints is that most American’s have been fingerprinted now, and therefore the national database for fingerprints is quite comprehensive. Not the case with dental records. But fingerprints don’t last long in the Cumberland River, and teeth are almost indestructible. DNA is usually fairly fragile, but is still quite accurate if the material has not degraded substantially. DNA testing is still usually quite time consuming and expensive, so it is used for identification purposes only as a last resort. This may change as all forensic sciences have become increasingly more sophisticated. A majority of all ID’s done at the World Trade Center tragedy were done by dental record comparison.
Now, back to our first laboratory experience with dental identification……We did need to resect the jaws of the corpse to gain adequate access to the most posterior teeth (those molars in the rearmost part of the mouth. Trying to balance my nausea with observing the first cut on the remains of what was once a human face was a bit difficult. ‘You just watch for now, so you can try and get used to this whole process.’ With that, he took a scalpel and made two incisions, at each corner of the mouth and extended to each ear. By releasing the soft tissue restrictions on our access, we were then able to reflect the lips and cheeks and visualize each tooth, all the way back to his wisdom teeth, which were still present. Remember, the rigor mortis was already gone, so the jaws would easily open and close now with no lingering stiffness.
Please pardon the short lesson in dentalanatomy and charting, but it will help to understand the process. For those of you who are ‘visual’, I will post below a sample of the dental charting. Left and right in dentistry is always referred to as the patient’s ( or decedent’s) left or right. Starting with the upper right wisdom tooth, we assign that as ‘tooth #1’. Then coming forward in progression, each tooth is numbered consecutively (the two front teeth would be #8 and #9) until you get around to the upper left wisdom tooth (which is #16). Then, dropping straight down to the lower left wisdom tooth, which is #17 and progressing around towards the lower front teeth (which are #’s 25, 26) and then finally around to the lower right wisdom tooth, which is #32.
Any natural tooth that is missing still keeps its numbered slot. In other words, if you have all your natural teeth except for your wisdom teeth, then your existing charting would show an ‘X’ on #’s 1,16,17,and 32. Make sense?
To take the process one step further, each of our 32 teeth have five sides to each tooth. If you imagine it as a cube, then the surface we chew with is called the ‘occlusal’ surface. The side next to the tongue is called the ‘lingual’ surface. The surface that touches your cheek is called the ‘buccal or facial’ surface. This leaves the last two surfaces which are in ‘in between surfaces’ or interproximal. The side of the tooth that is closest to the midline of your face is called the ‘mesial’ surface, and the one furthest away from the midline is called the ‘distal’ surface.
Now back to our poor chap at the morgue….once we got complete access to his oral cavity, we were able to fill a chart similar to the one that has been posted here on our blog. Starting with tooth #1, a clinical description was made on each tooth, first, is it even present or missing. If it has been extracted, then it is duly noted on the chart. If present, we look for a pre-existing filling in that tooth. If it has one then we schematically record which of those five surfaces was involved with that particular filling.
Forensic odontologists note on each tooth, which surfaces specifically, if any, that each tooth might have a filling in exists. Mathematicians tell us that the number of possible combinations is 5 to the 32nd power. That is a number larger than the total number of people that have EVER lived on our planet! Pretty strange, huh? That is one reason that dental identification is so dependably reliable.
