Posts for tag: x-rays
The CAT scan is a relatively recent technique in dentistry, used to get an image of what’s happening deep within your jaws. You may be wondering what a CAT scan tells us that a conventional x-ray picture does not, and whether it is worth the extra expense to get one. And how does a CAT scan compare with a conventional x-ray in terms of radiation exposure?
CAT stands for “computer assisted tomography.” Often it’s just called a CT scan, for “computerized tomography.” The word “tomography” comes from roots meaning “slice” and “write.” Tomographic techniques take repeated two dimensional pictures, similar to repeatedly slicing through an object, and then assembles them with a computer to produce a three dimensional (3-D) image.
The latest type of CT scan used in dentistry is called CBCT, or Cone Beam Computed Tomography. The Cone Beam refers to a spiral beam of x-rays, which is used to create a series of two dimensional images from which a computer creates a 3-D image. Such an image is of great value in assessing problems and planning treatment.
Here are just a few examples of how a CBCT scan can be used. Orthodontists can see skeletal structures and developing teeth that are still inside the jawbone while planning strategies for directing the teeth in order to arrive at a better bite. Oral surgeons can find impacted or missing teeth, see their locations, and view their proximity to nerves and sinuses, assisting them in planning surgeries. These scans are particularly useful for root canal specialists because they show root canals that are less than a millimeter wide and even reveal accessory canals that may not be visible on conventional x-rays. In cases of sleep disorders such as sleep apnea, a CBCT during sleep can be used to view a person’s airway and how it may be blocked by the tongue and other soft tissues in a person’s throat during sleep.
Compared to background radiation, the amount of radiation delivered in dental x-rays is minimal. A CBCT delivers a dose of radiation that is less than a typical full mouth x-ray series but more than a typical two dimensional panoramic radiograph. Generally CBCT scanners deliver lower doses than medical CT scanners.
With one low-dose CBCT scan, we can get an accurate idea of the internal structure of your bones and teeth and how they are situated in relation to each other. Prior to the availability of such images, many of these relationships had to be discovered in the course of a surgery or other treatment. Thus such a scan can aid greatly in the quality of treatment you will receive.
It’s important for your child’s current and future health that we watch out for tooth decay. Taking x-rays is a critical part of staying one step ahead of this common disease.
But while x-ray imaging is commonplace, we can’t forget it’s still a form of radiation that could be potentially harmful, especially for a child whose tissues are rapidly developing. We must, therefore, carefully weigh the potential benefits against risk.
This concern has given birth to an important principle in the use of x-rays known as ALARA, an acronym for “As Low As Reasonably Achievable.” In basic terms, we want to use the lowest amount of x-ray energy for the shortest period of time to gain the most effectiveness in diagnosing tooth decay and other conditions.
A good example of this principle is a common type of radiograph known as a bitewing. The exposable x-ray film is attached to a plastic devise that looks like a wing; the patient bites down on it to hold it in place while the x-ray exposure takes place. Depending on the number of teeth in a child’s mouth, an appointment usually involves 2 to 4 films, and children are typically spaced at six months apart. Frequency of x-rays depends on your child’s tooth decay risk: lower risk, less need for frequent intervals.
Each bitewing exposes the child to 2 microsieverts, the standard unit for radiation measurement. This amount of radiation is relatively low: by contrast, we’re all exposed to 10 microsieverts of background radiation (natural radiation occurring in the environment) every day or 3,600 microsieverts annually. Even two appointments of four bitewings each year is a fraction of a percent of the background radiation we’re exposed to in the same year.
This conservative use of x-rays is well within safe parameters for children. As x-ray technology continues to advance (as with the development of digital imaging) we anticipate the exposure rate to diminish even more. Prudently used, x-rays remain one of our best tools for ensuring your child’s teeth are healthy and developing normally.
If you would like more information on the use of x-rays with children, please contact us or schedule an appointment for a consultation. You can also learn more about this topic by reading the Dear Doctor magazine article “X-Ray Safety for Children.”