Want to know a secret? You think more of xrays than we do. Not a week goes by when I don’t hear the questions, “What does the xray show?” or the more accusing, “Didn’t that show up in the xray?” We need xrays, but they often don’t show as much as we’d like.
Xrays provide a way to see pathology that we can’t feel with our instruments or see with our enhanced vision. Xray diagnosis is dependent upon three variables; 1) the quality of the xray, 2) the ability of the x radiation to actually detect the problem and 3) the ability of the doctor to see the problem on the xray.
The quality of today’s dental xrays is actually quite good. With the advent of digital radiography, we have the ability to magnify the xray image. It’s amazing what happens when the small, traditional xray film which is only an inch and a half long is instead replaced by an image that is projected on a 37” video screen. Not only can I see the image better, so can the patient.
The ability of the xray to detect the problem is a bit more difficult to explain. The xray beam needs to penetrate the tooth structure in order to show an image. The harder the substance, the whiter it shows up on an xray. So enamel is on the lighter side. Dentin is grayer. Tooth decay, which is soft, shows up as a darker image. But if there is a metallic crown on the tooth, the metal reflects the xray. Xrays don’t penetrate metal. So anything that’s under a metal crown can’t be seen on the image. Pathology, which shows up as a darker structure, can be blocked by a lighter structure such as a root surface, so we can’t see that pathology. A CT-scan shows multiple images in different planes and is often better for identification of pathology. The three dimensional CT-scan allows us to see volume and particularly thickness of bone, so critical to assessing the volume necessary for a dental implant.
Our ability to read the xray comes with training and experience. Despite the fact that I’ve been doing this for a long time, I often send images to an oral and maxillofacial radiologist for his interpretation, particularly for pathology cases.
But as good as xrays might be, they don’t always tell the whole story. Years ago, I saw a gentleman who was missing all of his teeth, had a severely resorbed jaw, and couldn’t chew. I referred him for a CT Scan and found room for only two dental implants. Two dental implants are far better than none, but four dental implants would improve his chewing ability immensely. I then operated on the patient, and found enough room for the four dental implants that he had hoped for.
Xrays are great, but they are not the entire diagnosis. Together with some of the advanced imaging technology available today as well as experience and sound clinical judgment, they can be an excellent tool in helping your dentist make a better diagnosis.
Lee N. Sheldon, DMD