Dental x-rays are used to create detailed images of a patient’s teeth and mouth. They are created by a form of electromagnetic radiation in which the energy is high enough to penetrate the body and to create an image on film. Dentists can examine the images generated by an x-ray to detect abnormalities in the teeth or mouth that require treatment.

Objects and tissues in the mouth appear differently on an x-ray image depending on how many of the x-rays are able to penetrate the structure. The more thoroughly rays penetrate a structure, the darker it appears. Teeth and bones are relatively difficult to penetrate and appear in shades of off-white or gray (radiopaque). Because fillings or other metal dental restorations are often denser than teeth or bones, they show up as very bright white areas. However, the type of material used in the restoration dictates how light the image appears.

Parts of the mouth that are less dense or that contain air or fluid (e.g., cysts, tumors, infections) are more easily penetrated and appear either dark gray or black (radiolucent). Cavities show up as dark spots against the lighter-colored tooth. Infections and signs of gum disease also tend to appear darker. X-rays can differentiate particular parts of a tooth like enamel and dentin due to the differences in mineral content, which determines density.

X-rays are often used to monitor tooth growth and development in children. X-rays can reveal whether there is enough room in the mouth for the child’s permanent teeth to emerge and can detect abnormalities such as cavities, extra teeth (supernumerary teeth) and impacted teeth. When detected early on an x-ray, these conditions are often much easier to treat.

X-rays can be used to reveal dental problems in patients of all ages. X-rays reveal tiny pits of decay in the teeth that may not be evident during a visual examination. X-rays can also be used to detect decay under existing fillings or other dental restorations, as well as damage to such restorations and the following:

• Abnormalities such as cysts, infections and both benign and malignant tumors
  
  
• Bone abnormalities associated with diseases
  
  
• Infection, death of the nerve or other problems associated with the teeth and bones
  
  
• Injuries to the teeth or jaw (e.g., fractures)
  
  
• Periodontal (gum) disease
  
  
• Impacted teeth
  
  
• Extra teeth

A dentist may use a dental x-ray to help prepare and place dental restorations such as crowns, fillings, dental implants, and dentures. They are also used to plan orthodontic cases and aid in the diagnosis of traumatic injuries to the teeth and supporting structures.

Patients generally have their teeth x-rayed on a regular schedule as determined by the dentist. The patient’s age and history of dental visits and dental problems help dictate how often a person needs x-rays and the type of x-rays required. Some patients may need to have their teeth x-rayed every six months, whereas others will only require x-rays every two years. People visiting a new dentist are encouraged to ensure that previous dental records are forwarded to the new dentist.

Certain conditions and situations make more frequent x-rays likely. For instance, children are at high risk of developing cavities and need to have their tooth development monitored. As a result, they often need x-rays every six months to one year.

People with a history of extensive dental restoration may also require more frequent x-rays. Patients who have fillings and other dental work will require x-rays to ensure that decay has not formed beneath the restorations or in new spots.

Other conditions that may require more frequent x-rays include:

• Tendency to drink sugary sodas, chocolate milk, or coffee or tea with sugar. These beverages create a much higher risk for tooth decay, making more frequent x-rays prudent.
  
  
• History of gum disease. More frequent x-rays may be necessary for patients who have a history of periodontal disease that puts them at increased risk of bone loss.
  
  
• History of smoking. Smoking increases the risk of periodontal disease.
  
  
• Use of medications or history of diseases or treatments that promote dry mouth. Certain medications, diseases and treatments cause a condition in which saliva production is reduced (xerostomia). Saliva keeps pH levels in the mouth stable and helps to cleanse the mouth. When pH levels fall, minerals in the teeth can break down, leaving the teeth vulnerable to cavities. Medications that can cause this condition include antianxiety drugs, anticholinergics, anticonvulsants, antidepressants, antihistamines, antihypertensives, diuretics and narcotic pain relievers. Diseases include Sjögren’s syndrome, and treatments include radiation to the head or neck that damages the salivary glands.
  
  
• Other suspected dental diseases.