OPG & Dental
What is the test used for?
These are special x-ray techniques which look at the teeth and jaw.
An OPG (orthopantomogram) 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 and determine relationships of the structures of the lower face.
What is the preparation for the test?
No preparation is necessary other than the removal of jewellery in the region of your head and face, for example, ear rings, hair clips and false teeth. Metal will cause artifacts on the image, and may obscure abnormalities.
Where do I go for this test?
The dental x-ray machines are specialised pieces of equipment located at BMI Geelong Private Hospital and BMI Torquay Community Health Centre. There is also an additional OPG machine available at Geelong Hospital for Emergency Department access. BMI Geelong Private offers OPG as a 'walk-in' service, with no appointment necessary.
How is the test done?
You will be asked to stand with your chin resting on a small shelf to provide accurate positioning. For an OPG, you will be asked to bite gently on a covered mouth piece to steady your head. 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 generally taken with the face viewed from the side. (Lateral) The tempero-mandibular joints (TMJ's) are often the cause of facial symptoms. These are the joints of the lower jaw just in front of the ears. They allow your mouth to open and close. These are imaged using both a standard x-ray technique, and also specialised OPG views.
For detailed assessment of the bones and soft tissues (skin, muscle and glands) of the face, your dentist/oral surgeon may ask for a CT. This test generates cross sections of the face, and with the aid of computer, can produce three-dimensional images of the face.
What about the radiation dose?
Although the radiation dose associated with OPG and cephalometry is extremely low it is important that the procedure is performed using modern dose efficient equipment. In 2006 Barwon Health installed new digital OPG and Cephalometry systems that utilise direct radiography (DR) capture of the x-rays. This results in a potential dose reduction of 50% compared with conventional x-rays using either film or computed radiography (CR) phosphor plate technology. There are also specific paediatric dose reduction protocols.
For further information please refer to the FAQ's.