Taking a dental radiograph:
Step 1: Patient positioning
Position the patient so that the area of interest is convenient to the radiographic beam. In general, this is where the object is “up”. For mandibular canines and incisors, the pet should be in dorsal recumbency. Finally, for maxillary cheek teeth, the patient should be in lateral recumbency with the affected side up. For maxillary teeth, the patient should be in lateral recumbency with the affected side up. In our practice virtually all radiographs are exposed in lateral recumbency. This takes some getting used to but will decrease the number of times a patient must be rolled when doing surgical or endodontic procedures.

Step 2: Film Placement within the patient’s mouth
Place the sensor in the mouth so that the entire tooth (crown and entire root surface) is covered by the radiograph. Remember, the roots of all teeth are very long. This is especially true of canine teeth, which are longer than you think. Always err on the side of having the film too far in the mouth to ensure you do not cut off the root apexes. The sensor/plate should be placed as near as possible to the object (generally touching the tooth and gingiva) to minimize distortion.

Step 3: Positioning the beam head
There are two major techniques for positioning the beam head in veterinary patients. Both techniques are used daily in veterinary practice. Parallel technique: This is where the film is placed parallel to the object being radiographed and perpendicular to the beam. This is how standard (large) films are taken. This gives the most accurate image. Unfortunately, this is only useful in the lower cheek teeth in the dog and cat. This is because these patients don’t have an arched palate. The film cannot be placed parallel to the tooth roots because of the palate’s interference. Therefore, this technique is not always possible. Bisecting Angle Technique: This is the most common type of dental radiograph taken in veterinary patients. This uses the theory of equilateral triangles to create an image that accurately represents the tooth in question. To utilize this technique, the film is placed as parallel as possible to the tooth root. Then the angle between the tooth root and film is measured. This angle is cut in half (bisected) and the beam placed perpendicular to this angle. This gives the most accurate representation of the root.  

The “Simplified Technique” as developed by Dr. Tony Woodward does not utilize direct measurement of any angle, instead relying on approximate angles to create diagnostic images. There are only 3 angles used for all radiographs in this system 20, 45, and 90. Mandibular premolars and molars are exposed at a 90-degree angle, maxillary premolars and molars at a 45-degree angle, and incisors and canines at a 20-degree angle. To initiate any radiograph, place the film in the mouth and set the positioning indication device (PID) perpendicular to the film. For mandibular cheek teeth, this is the correct placement. For the maxillary premolars and molars, rotate the beam to a 45-degree angle. For the incisors and mandibular canines rotate 20 degrees. For the maxillary canines an additional rotation 20 degrees lateral is necessary to avoid superimposition of the first and second premolars.

Step 4: Setting the exposure
If you are using a machine where you set the exposure manually, you will need to set up a technique chart like one for a standard (large) unit. The good news is that there is only one variable that needs to be adjusted. If you are utilizing the computer-controlled system, set the buttons for the species, size of the patient, and tooth to be imaged. If you have correctly set the machine and the image is incorrectly exposed, the easiest way to adjust is to change the time setting up or down.

Step 5: Exposing the radiograph
Dental radiograph machines have a handheld switch to expose the radiograph. If it is possible, leave the room prior to exposing the radiograph. If it is not, stand at least 6 feet away at a 90 to 130-degree angle to the primary beam (meaning to the side or back of the tube head, not in front or behind). Once everything is set, press the button. It is important to remember, that these switches are “dead man’s”. This means if you let up during the exposure, it will stop the production of x-ray beams. On a standard unit, this will make a light radiograph, on a computer controlled one it will give an error message and you will need to start over. Make sure you hold the button down until the machine stops beeping.