Your son just had “X-rays” taken at the dentist last month. Why does the orthodontist need to take another one? In fact, why do orthodontists need X-rays at all?
X-rays, officially called radiographs, are images created when a beam of radiation passes through the body and hits a sensor (or a piece of film in older machines) on the other side. X-rays have the ability to create pictures revealing the differences in the densities of the tissues through which they pass. The “shadows” cast on the digital sensor or film allow doctors to see objects hidden by the skin and bone. The most common X-rays taken by general dentists are called bitewings. In a bitewing, the dentist gets a detailed picture of a small group of teeth that reveals the health of the enamel, inner canals, and roots. Enamel and fillings are dense and appear white in color on the radiograph. The bone around the teeth, the root canals, and decay are less dense and therefore appear darker. Dentists are trained to interpret the light and dark patterns so they can distinguish normal tissues from abnormal ones.
X-rays are essential in orthodontics for many reasons. First, orthodontists are also dentists and, although they are focused on different things, they share the responsibility of identifying pathologies if they are present. These include abscesses, tumors, and other things that are not necessarily directly related to straightening the teeth. Although rare, such pathologies are many times identified for the first time by orthodontists and lives can be saved as patients are referred for treatment.
The second reason orthodontists take X-rays is to help them diagnose and treat orthodontic problems. Orthodontic X-rays focus more on the position and form of the teeth and jaws than on individual teeth like bitewings. Orthodontists are especially interested in missing, extra, impacted, or misplaced teeth, and short, long, or misshaped roots. Problems with the jaws include bones that are too big, too small, asymmetrical (off center), too far apart, too close together, or misshapen. X-rays provide orthodontists with essential information that helps them determine where problems exist and the best way to correct them. The size, shape, and position of the teeth and bone in X-rays dictate if surgery or tooth extraction will be necessary.
Orthodontists also take X-rays during treatment so they can monitor how treatment is progressing. Not all effects of orthodontic treatment are visible to the naked eye. Although very rare, moving teeth in some individuals (about 2%) causes the roots to shorten. Orthodontists must check for this during treatment so they can determine if and how long tooth movement should continue. Sometimes orthodontists observe how the teeth are moving to help them finalize the treatment plan. I prefer not to remove permanent teeth if possible, so in many borderline crowding cases I will begin to align the teeth just to see how the teeth and bone respond. If the progress X-ray reveals that there is not enough bone to accommodate all of the teeth, I can always have some removed along the way.
After treatment, a final X-ray is taken to evaluate the outcome of treatment and make recommendations for other necessary procedures (i.e. wisdom teeth). Ideally then, I take one radiograph at the beginning of treatment, one after about six months, and one after the braces come off. Each of these X-rays exposes a patient to less radiation than they would receive taking a typical airplane flight. All dentists are taught to use the ALARA principle (As Little As Reasonably Achievable) when it comes to radiation. I am careful to take X-rays on my patients only when it is in their best interest, and I assume that my colleagues also do the same. Don’t be afraid to ask your orthodontist the reason for your next X-ray.