Saturday, May 15, 2010

X-rays in 3D?

Now that we have all seen the movie Avatar in 3D, some of us more than once if you believe the attendance figures, let me tell you how we use 3D imaging in dentistry. We have recently installed a cone beam 3D X-ray machine at Los Gatos Dental Group.

I admit that our motivation was primarily to make implant placement safer and more predictable. But what I have seen in six weeks of reading the 3D X-rays that we have taken has convinced me that we should be imaging everybody in 3D, not just implant patients.

Take this case, a young woman who has had multiple visits to her physician complaining of sinus congestion. She has been repeatedly treated for sinus infections and other presumably allergy related symptoms to little avail.

This is an X-ray, that is at right angles to the traditional X-ray, and which has been generated by our 3D X-ray machine. At the left end of the yellow line is an abscess, at the end of a root canal treated tooth, that has invaded the sinus. The cause of her sinus infection is this abscess, which is not visible on the traditional 2D X-ray, because the darkness is hidden by dense bone both in front of and behind, as well as the root of the tooth. The tooth doesn’t hurt, so nobody has connected the repeat infections with a tooth.

The next image is another at right angles to the traditional X-ray. What you see at the end of the yellow line is another abscess at the apex of a root canal treated tooth. This tooth is also asymptomatic, so far. The abscess has just broken through the palatal plate of bone and is progressing towards the palate. Left untreated, this will likely begin to swell and hurt in the roof of her mouth. By diagnosing this sooner by 3D X-ray, instead of later by 2D X-ray, we have prevented pain and swelling.

Now that I have been able to make these and other diagnoses by 3D, I can’t imagine going back to 2 dimensional radiography. But we are finding other uses for the images created by 3D radiography.

I have been able to identify places where extra nerves enter the lower jaw. These extra nerves can innervate teeth in ways that dentists were not taught to numb. Most of the people who have these extra nerves to teeth are terrified, because dentists have not believed them when they have said that the tooth wasn’t numb. After all, we were taught in dental school that if your lip is numb, your lower teeth on that side are numb. I have long suspected the existence of these nerves, but I have had to find them by trial and error. SInce I have been sedating anxious patients my entire career, I have seen more than my share of people with this anatomical difference. Now I can see this before the tooth doesn’t get numb with the usual anesthetic technique.

I spent last weekend in Florida studying the Poly Jaw Replicator. This instrument takes measurements in 3D from these X-rays to a jaw simulator, that is the first instrument to truly reproduce the actual jaw movements to such accuracy. The benefit will be comfortable crowns and bridges with little or no adjustment. The amount of time it will take to deliver complete mouth dentistry will be dramatically reduced, and the need for another visit to finalize the bite, when you are not numb, will vanish.

As these instruments become more widely accepted by dentists, their price will come down. I predict that most dentists will be using 3D radiography within ten years, as it becomes the standard of practice. The public will demand more complete and earlier diagnosis.