What is the test used for?

An OPG ("orthopantogram", shown at right) gives a panoramic view of the mouth, giving information on the teeth and the bones of the upper and lower jaw.

Cephalometry is used to obtain measurements of the structures of the lower face.

What is the preparation for the test?

For some cephalograms, some dentists and oral surgeons like us to "paint" a stripe of barium paste on your face to allow them to measure more accurately. Otherwise, no preparation is necessary.

Will I have to undress?

You will not have to undress, but will be asked to remove any removable jewellery in the region of your face and head. Metal will cause artifacts on the x-rays, and may obscure abnormalities.

Where will I be for the test?

The dental x-ray machines are specialised pieces of equipment kept in our general x-ray room. You will be asked to stand with your face resting on a small shelf to provide accurate positioning. For an OPG, you will be asked to bite gently on a sterile mouth piece to steady your head. The radiographer will guide you through it all, and the examination is almost never uncomfortable.

How is the test done?

An OPG aims to view the jaw, while blurring out the other structures of the face and skull. This is done using a technique called "tomography". As the X-ray tube moves around your head, the x-ray film moves in the opposite direction behind your head. This generates an image where the jaw is in focus, and the skull is blurred.

Cephalograms are taken in one or both of two planes: anterior, where the face is viewed straight on, and lateral, where the face is viewed from the side.

Does it hurt?

No.

How long will it all take?

5–15 minutes depending on the number of views required.

And after the test?

You can go home. If you have to take the films and report with you, there may be a wait of about 1 hour to allow for film processing, interpretation by the radiologist and typing.

Does the test use radiation?

Ionising radiation is used.