Dental X-Rays

For the past 5 days at the clinic I was on an internal rotation with the radiology department, which essentially means, that I take X-rays of other students' patients each and every day. I didn't see any of my own patients, which made the week void of all stress, and I got better at taking and reading radiographs (more appropriate than X-rays in this case).

And since everyone gets these when they go to the dentist, I decided to explain what is being looked for during this process. The above image is called a panograph which shows the dentist major bony/teeth structures throughout the head and neck. This is important for erupting teeth, discovering possible problems in the nodes and noting bone resorption.


This type of image is called a bitewing. It's taken of the back teeth (only) to look for decay through the tooth. The whitest areas are those in which the least amount of radiation passes through. Thus the whitest areas are silver fillings. Here the dentist is looking for consistent shape and shade on the film. Areas of decay will show uncharacteristically darker than surrounding tooth structure. This indicates decay and soft spots in the tooth. The red arrows point to dark areas under the metal filling. You can notice the density is different from the rest of the tooth structure. CAVITY! The filling has to be taken out along with the decay. The green box highlights healthy tooth structure = what you hope you see on your teeth. Notice the consistency of the outer layer of tooth (enamel) all the way around.


Here you can see cavities on two teeth next to each other. Notice how the consistent density of the image at near the roots is altered near the biting surface. You can see darker areas of structure where bacteria and acid have eaten away at the tough outer layer of enamel and are approaching the pulp of the tooth which contains nerves and blood vessels. One common rule of thumb here is that decay often extends 30% farther that one can see from a radiograph.


A cavity that reaches the pulp will cause the infected tissue to spread to the apex (tip of the root) of the tooth. The dark circle around this tooth is an abscess. These are often associated with pain, but not always. This tooth must be treated by root canal therapy, which isn't as bad these days as everyone says it is.

All right, now you know. Ask your dentist to show you what he finds on your radiographs next time. He/she will be glad to explain. Once you know where problem areas are, you can change how you brush and floss to improve your prevention.