Why so detailed?
If we control the variables involved with positioning the patient and the sensor, the only variables we must approach from
this point is the position of the tube head and its angulation that is read off the unit as previously described.
In addition, each patient requires very similar tube-head positioning. The tube-head position and angulation for caudal cheek
teeth in a small dog and that of a large dog are very similar.
Once you get used to taking that view in any dog, you will become familiar with the approximate position and angulation of
the tube head. You should be able to consistently reproduce it in future patients.
If the patient and/or the sensor are positioned a different way each time, then the tube-head angle and position suddenly
become confusing variables.
Tube-head angulation and position
With dog and sensor positioning controlled, the tube head should be set at an angle of 45 to 70 degrees to produce an image
that is reasonably close to a similar image taken if parallel technique were possible (Photo 6).
Photo 6: An example of the caudal-to-rostral oblique view for imaging the caudal maxillary cheek teeth in the dog. The tube-head
angle is 55 degrees.
In the cat, the same is true except for the caudal maxilla. Angle settings should approximate 30 to 40 degrees for an intraoral
view in the cat. This is to avoid superimposition of the zygo-matic arch over the image. Slight elongation of the caudal cheek
teeth occurs due to this narrow angle.
Tube-head positioning falls into four general categories:
» caudal to rostral oblique
» rostral to caudal oblique
Table 1 offers more guidelines.
Table 1: Recommended tube head position for dog and cat
Various devices can be used to help position the digital sensor within the mouth so that it stays in the desired position.
Gauze, paper towels, flexible hair curlers and other positioning aids can be used. The author makes custom foam wedges by
cutting blocks slightly larger that the sensor and then using scissors to create a slot to place the sensor. This allows positioning
for the premolars and incisors in the dog and protects the sensor in case it is dropped. Paper towels are folded in various
shapes and wrapped to produce positioning devices and gags (Photo 7).
Photo 7: An example of the caudal-to-rostral oblique view for imaging the caudal maxillary cheek teeth in the dog. The tube-head
angle is 55 degrees.
Increasing the friction of the sensor against the oral cavity helps decrease sliding of the sensor once it is properly positioned.
An inexpensive way to accomplish this is to snip the finger out of an exam glove and place it over the sensor. This replaces
the slick inserts that are provided with the sensor kit.
It is important to practice taking dental radiographs on a skull to obtain reasonable proficiency prior to approaching an
anesthetized patient. The bottom of the digital sensor has an often-cumbersome extension at the cord interface. Silly putty
can be molded to the bottom of the sensor on either side of this extension to provide a straight surface, making positioning
easier when practicing on skulls (Photo 8).
Photo 8: Silly putty is used to provide continuity to the sensor anatomy to maximize ease of positioning when working with