John W. Bristow D.D.S

Changing the world, one smile at a time…
(707) 642-3319


Why are X-rays important?

Radiographs, commonly known as X-rays, are an important tool to help Dr. Bristow properly diagnose your oral health needs. They allow us to see beyond what the naked eye can see. X-rays help us determine if you have dental caries (cavities), periodontal (gum) disease, abscesses or abnormal growths, such as tumors or cysts. They also show the location and condition of impacted or unerupted teeth.

How often should X-rays be taken?

How often X-rays are taken and what types Dr. Bristow recommends is based on his responsibility to do a complete exam and to ensure that problems are detected early to minimize damage to your teeth and/or gums. It also depends on the condition of your mouth, the degree of problems present, and what parts of your mouth we need to see. If you had X-rays taken recently and then see us, you can request a copy of your X-rays be sent to your us.



Bitewings are one of the most common sets of X-rays. Bitewings show teeth above the gum line and the height of the bone between teeth. Bitewings help diagnose gum disease and cavities between teeth. The bitewing X-ray is placed on the tongue side of your teeth and held in place by biting down on a plastic tab. Normally four bitewings are taken as a set. They may be taken as often as every six months for people with frequent cavities or every two or three years for individuals with good oral hygiene and no cavities.

Full Set

A “full-set” of X-rays shows all of your teeth and all of the surrounding bone, Helping to diagnose cavities, cysts or tumors, abscesses, impacted teeth, and gum disease. A full set usually consists of 14-20 individual X-rays and is generally recommended during the first visit with us to aid in proper diagnosis and treatment planning.


A panorex is a full-mouth X-ray that is taken without ever putting an X-ray film into your mouth. Instead, as you sit still, the X-ray head rotates around you, providing one large image of your jaws and teeth. This type of X-ray is particularly helpful for seeing the upper and lower jaws at one time and can show impacted teeth or other hidden structures that could be hard to see on the small, individual film used for a “traditional” full-set.

Periapical (PA)

A periapical (PA) X-ray refers to a single X-ray that is taken to show a specific area of concern. If you have a tooth ache, we are
likely to recommend a PA film to see that whole tooth including the root.

Cone Beam Computed Tomography or 3-dimensional X-rays

Advances in technology continue to provide new ways to see structures that cannot be seen by the naked eye. One of the newest of these imaging technologies is cone beam computed tomography (CBCT). CBCT uses rotating x-ray equipment, combined with a digital computer, to capture clear, 3-dimensional pictures of soft tissue, bone, muscle, and blood vessels. Dr. Bristow may recommend use of CBCT or other new imaging technologies when he feels additional imaging is necessary for proper diagnosis or treatment.

How much radiation is there with dental X-rays?

A bitewing set consisting of four X-rays, exposes the patient to 22 to 51 microSv (microsievert).

A panoramic examination results in exposures of about 5 to 25 microSv.

Cone-beam X-rays result in a wide variety of exposure ranging from a little as 20 microSv to as much as 700 microSv depending on image size and the brand of cone-beam machine used.

To understand what this means, this can be compared with the average amount of background radiation (radiation occurring in the environment) a person is exposed to in a year. That average, worldwide, is 2400 microSv per year.

Are there things we can to do limit my dental X-ray exposure? Yes. we take several steps to ensure you receive the least
amount of exposure possible when X-rays are taken.

1)Place a leaded shield over your body. A thyroid collar that shields your neck, while not mandatory, is often used.
2) Use a collimator, which is a long tube that extends from the X-ray machine. Collimators limit the size and shape of the useful x-ray beam reaching you.
3)We use digital sensors, which use a fraction of x-ray exposure of traditional x-rays.

In recommending X-rays, we follow the ALARA principle (As Low As Reasonably Achievable), to reduce radiation exposure to our patients by: determining the need for and type of X-rays to take; using “best practices” when taking X-rays, including the application of quality control procedures; and reading the images completely and accurately.

X-rays are an important diagnostic tool for us. Early detection and treatment of disease is the best way to ensure a healthy mouth over a lifetime. We recommend only the X-rays needed to ensure your optimum oral health. If you have questions or concerns about the types or frequency of the X- rays your we recommend, don’t hesitate to ask us.