When it comes to evaluating a pet’s teeth, dental x-rays are the best way to see what’s happening “under the surface.” That is, under the gumline.
Dental radiographs help you obtain a full picture of tooth roots, evaluate for periodontal disease and damage, differentiate between different types of FORLs, and look for any other defects that may not be visible with your eyes alone.
Even though the value of dental radiographs (to both your patients and your practice) is hard to deny, there can be a learning curve when your team first begins to use them.
This is important, because in order for your x-ray images to be diagnostic, they need to be good quality.
Fortunately, with practice, dental x-rays become simple and routine—a process your team can quickly replicate for each patient.
Establishing a Dental X-Ray Routine
To make the dental radiograph process easy for you and your team—and as quick as possible for your patients—it’s best to establish a repeatable routine.
This means taking the same shots, in the same order, each time.
You may need a larger number of views depending on the patient’s size and the angle of their mouth, but in general you can start in the same place each time and move through your views systematically until images of all teeth and their roots are captured.
Use your digital software to set up the views in the order you prefer.
Once you establish a routine, it will only take a few minutes to shoot all views for a small patient. And large dogs should take a maximum of 15-20 minutes.
Positioning the Patient
Your patients will be under general anesthesia for their dental procedure, including dental x-rays.
After intubation, leave the patient in sternal recumbency, and simply place a towel under their chin to keep their maxilla parallel to the table. Then obtain your views of the maxillary teeth.
When you finish the views of the maxilla, move the patient to dorsal recumbency, this time using a towel or other prop under their neck to keep the mandible parallel to the table as you obtain your views of the mandibular teeth.
You can use a trough or sandbags to stabilize the patient and keep them from tilting to the side, if needed.
Adjust this plan if you find that another method better suits your needs. For example, you may find that lateral recumbency works best for you for some views.
Whatever system you choose, we recommend repeating the same steps each time and using a method that minimizes the number of times you need to move the patient.
Sensor or Film Placement
Select the right size sensor or film for your patient. For most veterinary patients, this would be either a size 2 (for small dogs and cats, or views focusing on a single tooth) or a size 4 (for large dogs, or for full-mouth/whole quadrant radiographic views).
Whether you’re using a sensor for digital x-rays, or regular dental film, placement is important to ensure you can see all of each tooth root. Remember the roots are much longer than the crowns (twice as long with canine teeth), so position your sensor accordingly.
Finally, determine which side of the sensor or film should be positioned toward the x-ray beam. This may be indicated by a small dot or “dimple” on films. If you have a digital sensor, the cord side should face away from the tube and the cord should exit the front of the patient’s mouth.
Beam Placement
A parallel angle is used for the mandibular premolar and molar teeth. For many pets, this part of the mouth allows the sensor to be placed parallel to the teeth, and the beam to be shot straight forward (perpendicular) into the sensor.
The rest of the mouth, however, prevents this placement (the palate and mandibular symphysis get in the way). So, you’ll need to use a bisecting angle for the rest of your shots (and possibly for the rostral mandibular premolars).
A bisecting angle might seem complicated, but it’s important—choosing the correct angle prevents distortion (lengthening or shortening of the tooth root in your image).
Here is how to determine the bisecting angle:
Position the sensor within the mouth behind the teeth you want to x-ray, as if the patient is biting on it (use gauze or other aids to hold the mouth open so there is no pressure from the teeth that could damage the sensor).
Estimate the angle between the tooth root and the plate.
Divide this angle in half, and draw an imaginary line with your mind.
Position the x-ray beam perpendicular (at a right angle, or 90 degrees) to this line you’ve just imagined.
If the tooth root is too long on your image, raise the angle of the tube relative to the sensor. If the root is too short, lower the angle of the beam (move it more parallel toward the sensor).
Developing a Simplified Technique
Using a simplified technique can allow you to skip the bisecting angle measurement. For example, one described technique uses just three angles for all oral views…
90 degrees for mandibular molars/premolars.
70 degrees for maxillary molars/premolars.
45 degrees for canines and incisors.
Since you can position these angles on your tube head without measuring (many units have predetermined angles marked by the tube head), this makes positioning much easier and faster for you and your staff.
Exceptions, Views of Specific Teeth, and Further Training
These guidelines are a good starting point for many patients. But, you may find you need to adjust your views to accommodate certain dogs and cats, depending on the shape of their mouth and tooth roots.
Cats in particular may need steeper angles than dogs to minimize interference from the zygomatic arch. And some patients will have tooth roots that curve significantly.
For all of these reasons, and for the benefit of hands-on experience, it helps to schedule a demo of your equipment, or to find an in-person training opportunity for your staff. That way, you can maximize your return on investment by using your dental radiography unit to its fullest potential.
Any time spent developing the proper technique for positioning will be well worth it, as you’ll be able to quickly take views that aid your treatment decisions and deliver value to your clients.
Disclaimer: This article is for general informational purposes only, and not intended as a guide to the medical treatment of any specific animal.
Written by: Dr. Tammy Powell, DVM
