X-rays are divided into two main categories, intraoral and extraoral. With intraoral X-rays, the X-ray film is inside the mouth. With extraoral X-rays, the film is outside the mouth.
Intraoral X-rays are the most common type. They give a high level of detail. These X-rays allow dentists to:
The various types of intraoral X-rays show different aspects of the teeth:
Highlight the crowns of the back teeth. Dentists take one or two bite-wing X-rays on each side of the mouth. Each X-ray shows the upper and lower molars (back teeth) and bicuspids (teeth in front of the molars). These X-rays are called "bite-wings" because you bite down on a wing-shaped device that holds the film in place while the X-ray is taken. These X-rays help dentists find decay between back teeth.
Highlight only one or two teeth at a time. A periapical X-ray looks similar to a bite-wing X-ray. However, it shows the entire length of each tooth, from crown to root.
Depending on your oral health and dental history your dentist may recommend a full-mouth radiographic survey, or FMX. This includes every tooth, from crown to root to supporting structures. They are X-rayed using both bitewing and periapical radiographs. This is possible for both tooth decay and periodontal disease to be missed during a clinical exam, and radiographic evaluation of the dental and periodontal tissues is a critical segment of the comprehensive oral examination. The photographic montage at right depicts a situation in which extensive decay had been overlooked by a number of dentists prior to radiographic evaluation
The Safety of Dental X-rays
The benefits of X-rays are well known: They help dentists diagnose common problems such as cavities, gum disease and some types of infections. X-rays allow dentists to see inside a tooth and beneath the gums. Without them, more disease would go unchecked. Treatment would begin later. As a result, people would have more pain and lose more teeth.
The X-rays used in dental and medical offices emit extremely small doses of radiation. It is of primary concern to dentist to limit the exposure of our patients to radiation. That’s why experts say that X-rays should be used with caution and only when necessary.
Less Radiation for Safer X-Rays
Several changes have reduced radiation exposure in dental X-rays through the years:
The single most important way dentists keep their patients safe from radiation is by limiting the dose. An X-ray machine is quite large, but the X-rays come out of a small cone. This limits the rays to an area less than three inches in diameter. X-ray machines also are well shielded. Very little radiation exposure occurs beyond the diameter of the beam. One dental X-ray taken with an analogue dental film is equivalent to 2.5% of the exposure one would receive from a chest X-Ray.
The speed of films used for dental X-rays has been improved. This means that less exposure is needed to get the same results. Dentists who use the fast speed film (D-Speed) limit the amount of radiation needed to obtain a good picture. Therefore, patients also are exposed to less radiation.
The use of digital X-rays reduces radiation by as much as 80%. Today more dentists are using this type of X-ray. It’s estimated that as many as one-third to one-half of U.S. dentists use this technology. At Restorative Dental we use primarily digital radiography.
Dental patients used to hold X-ray film in their mouths with their fingers. Those days are long gone. Now, holders keep the film in place.
Before you get X-rays, you will be covered from the neck to the thighs with a lead-lined full-body apron. This lead apron has a neck protector, called a thyroid collar. The American Academy of Oral and Maxillofacial Radiology recommends the use of a thyroid collar on patients under age 30. Younger adults and children are at greater risk for radiation-induced thyroid cancer than older adults. These shields have been used for decades. Today, however, they offer more peace of mind than actual protection. That’s because modern dental X-ray machines emit almost no scatter (stray) radiation.
Dentists take X-rays only when they believe they are necessary for an accurate dental assessment or diagnosis.
Current guidelines say X-rays should be given only when needed to diagnose a suspected problem.