What is it?
The abbreviation OPG stands for orthopantomograph. The name appears complicated, but in simple words, it is a two dimensional X-ray image of the entire lower face and jaws. The OPG picture includes the teeth, the maxilla, the mandible, and the temporomandibular joints, in addition to several other oral structures.
Some simpler terms are: panoramic (dental) x-ray, panorex, panoral, or full mouth x-ray.
The OPG provides the dentist with very useful information on the patient. If a single tooth is to be treated, an ordinary x-ray apparatus for teeth may be used. This apparatus and its use costs much less.
However, when treatment for a number of teeth is being planned, or a general restoration is required, OPG is the starting point. It also has the advantage that no film or slide has to be placed inside the mouth of the patient. In addition, the level of radiation intensity used is less in the OPG than the ordinary dental x-ray.
The orthopantomograph shows all the teeth – erupted or hidden – in their correct relative position. It assists the dentist in assessing periodontal bone loss and various other abnormalities. Thus, it is a wonderful tool for the dentist, as it helps him in planning a correct and well-informed strategy for restoration, implants, or for preparation of a denture.
Despite numerous benefits of the dental OPG, the foremost limitation of this radiographic technique is the lesser extent of detail visible for each tooth, when compared with other radiographs, such as the periapical or occlusal x-rays. Hence, an OPG cannot be used to diagnose a dental anomaly, due to the limited amount of “local” detail available.
Taking an OPG of a patient is a very simple procedure, for both the patient and the technician operating the machine. The machine is basically a small x-ray unit mounted on a vertical column, such that its vertical position can be adjusted up and down the column to align the x-ray unit with the face of the patient. The unit can also move a full circle in azimuth.
The patient is asked to place his or her chin on a specially built support, which is also adjustable on the column to suit the height of the patient. The patient is made to stand in the standard vertical position, the x-ray unit adjusted in height and azimuth. The patient is asked not to move the head or jaws during the next few seconds as this can blur the picture.
Once triggered the x-ray unit moves a full circle horizontally around the head of the still patient, under computer control. It takes multiple slice x-rays from various angles in a horizontal plane. The x-ray energy passes through the face of the patient and hits a monitor diagonally opposite which also moves with the x-ray transmitter. The computer records all the data and with the help of special software prepares a two dimensional panoramic image for the dentist.
No complicated preparation is necessary. The patient is asked to remove all jewelry, and metallic objects about the face, head, and neck. Any dentures containing metallic objects can also interfere with the image, and if removable, should be removed.
Similarly, if the patient is wearing glasses, or a hearing aid, those are also removed. The patient is then asked to rest his/her chin on the designated fixture, and brought to the standard position. He/she is cautioned to stand still and not move the head or jaws while the machine is operated.
Since the procedure involves x-ray radiation, certain precautions must be taken just like in the case of any x-ray procedure. The radiation dose is carefully controlled as excessive exposure to radiation can be harmful for any human beings. Special care must be taken when dealing with infants and pregnant females. The radiographer will ask females about possible pregnancy before going for the procedure. In case of pregnant female patients, it is best to defer any radiographic exposure until after the delivery. However, if there is a dental emergency, a radiograph is taken by making the patient wear a lead apron, in order to protect the mother and the developing baby.