An Introduction to Veterinary Radiography
Dental radiographs are essential for the proper diagnosis of oral pathology in our dog and cat patients.
By Denise Rollings, AAS, CVT, VTS (Dentistry), Key Account Manager, iM3 | 2025
Many oral and dental diseases cause inflammation and discomfort for our patients, even if they do show outward signs. Most of the pathology is below the gingival margin, making it difficult or impossible to see on an oral examination alone.
Types of Interaoral Radiography Equipment
There are three main types of intraoral radiography systems used in veterinary dentistry: standard dental X-ray film with a chairside developer darkroom, direct digital imaging (DR), and indirect or computed digital imaging (CR). Each system requires a generator to produce the radiation needed for exposure, sending a precise amount to the tube head.
The X-Ray Generator Tube Head & Technical Adjustments
The tube head is the position-indicating device (PID) and may also be called the “cone.” The PID is what is aimed at the area of the mouth to be imaged. The exposure time, voltage (kVp), and milliamperage (mA) may be adjustable depending on the generator using the control panel. The control panel has preset settings based on the size of the patient and the area of the mouth being imaged to help produce the best exposure for that image.
Different Types of Generators
Generators may be mounted on stands (trolley), walls, or be handheld. A wallor ceiling-mounted system requires that the station where the dental radiographs will be obtained is within reach. The trolleymounted system may be moved to diff erent stations. The use of a trolley system may be prohibited by the floor space of a clinic. A handheld generator needs the least amount of space and may be moved to different stations for use. State laws vary regarding generator use and must be followed.
Dental X-ray Films
Dental X-ray films are much less common today but are still (rarely) in use. In this method, the film is placed into a protective cover and, after exposure, is developed in a small chairside developer using chemicals. This process can take several minutes, and the resulting image is evaluated using a light source behind the film. While familiar to some practitioners, the system is slow and requires chemical maintenance.
Direct Digital Imaging (DR)
uses a hard sensor connected to a laptop or generator via a cord. The sensors typically come in sizes 0, 1 and 2, with size 2 being the most common. A few companies, such as iM3, offer a size 4, and a size 6 digital sensor. Due to the high cost of sensors, most facilities only purchase one size. Once exposed, the image is transferred to the computer and viewable within seconds. DR systems are the fastest and require the least radiation, but they may be limited to a size 2 sensor, meaning larger patients require multiple images for a single tooth or larger area of the mouth unless a size 4 or 6 digital sensor is used.
Indirect or computed digital imaging (CR)
uses reusable phosphor plates, which are available in sizes 0 through 6, depending on the manufacturer. The plate is placed in a protective sheath before positioning in the patient’s mouth. After exposure, the sheath is removed, and the plate is inserted into a scanner. The scanner converts the data into a digital image, erases the plate, and allows it to be reused. This system can develop an image in as fast as 6 to 8 seconds depending on the manufacturers and settings. A CR system requires a supply of protective sheaths. CR plates are thin, flexible and available in larger sizes, making them comfortable for patients and offers the ability to obtain full mouth radiographs on a large-breed dog patient in as few as six images.
The iM3 CR 7 2.0 (left) processes one phosphor plate at a time, while the iM3 CR 8 (right) processes two simultaneously to help save time.
full-mouth dental X-Ray images taken on a large dog using a size 5 CR plate
Dental Imaging Software
Both DR and CR systems work with dental imaging software that allows the user to adjust brightness, contrast, rotation, inversion and magnification. Areas of the radiograph may also be circled, and pathology may be pointed out to the patient’s owner.
Most dental radiograph software systems allow the user to use full-mouth templates. These templates are preset with the order in which the user would like to obtain their dental radiographs and reduce the amount of computer time needed. These systems vary in cost, upkeep and features. It is important to research each system’s cost, maintenance needs, technical support, warranties and training options before a purchase is made.
Why Radiograph Teeth?
Dental radiographs are an essential part of a comprehensive oral examination. Full-mouth radiographs should be obtained for every dental patient, as most of a tooth’s structure lies below the gumline and cannot be assessed visually. Radiographs are critical for accurate evaluation, diagnosis, treatment planning and monitoring of pathology.
In human dentistry, patients can localize discomfort and undergo pulp testing, but veterinary patients require general anesthesia and cannot communicate pain, requiring a comprehensive oral examination and full-mouth radiographs.
Client education plays a significant role in gaining acceptance for dental radiographs. Human dentists have already educated their patients on their importance, but pet owners often require more explanation.
Using visual aids such as case examples, photographs, textbooks and before-and-after radiographs can help demonstrate the value of imaging. Many practices now include full-mouth radiographs with their dental procedures and do not make it an option, as it is mandatory.
Diagnostic Criteria
To be considered a diagnostic dental radiograph, a dental radiograph must show every part of the tooth not visible to the naked eye. There must be at least 2 to 3 mm of bone visible around the apex of the tooth root and the alveolar margin on each side. Images should have minimal elongation and foreshortening, and exposure should be appropriate — not too light or too dark. Some clinicians prefer to include the tooth crown, but this is a matter of personal preference.
Radiographic Concept & Positioning
To be considered a diagnostic dental radiograph, a dental radiograph must show every part of the tooth not visible to the naked eye. There must be at least 2 to 3 mm of bone visible around the apex of the tooth root and the alveolar margin on each side. Images should have minimal elongation and foreshortening, and exposure should be appropriate — not too light or too dark. Some clinicians prefer to include the tooth crown, but this is a matter of personal preference.
The Challenge of the Hard Palate
Dental radiographs on dogs and cats can be a challenge due to the hard palate. Humans have a high palatal vault, making the positioning of the sensor easier because the plate can be placed behind the teeth. Dogs and cats have a flat palatal vault, requiring the teeth to be placed on the plate and the use of angles to obtain the radiograph. This is called the bisecting angle technique. The only place we can place the sensor is directly behind the teeth in the caudal mandible. This is called the parallel technique, with the tube head aimed directly at the plate.
Think of the parallel technique like obtaining an abdominal radiograph of a dog. The dog is laying directly on the table and the beam is aimed directly at the dog. The parallel technique may sometimes be used for the mandibular incisor and canine teeth depending on the film placement and anatomy of the patient. The plate cannot be placed parallel to the teeth in the rostral mandible due to the mandibular symphysis, or anywhere on the maxilla due to the hard palate.
The Shadow Analogy
Think of the radiographic image as a shadow. We all remember playing with flashlights as kids. We can make the shadow long, we can make the shadow short, we can make the shadow move forward and we can make the shadow move backward. The same principle applies to dental radiographs. We are projecting a shadow of the teeth onto the plate in the mouth.
For example, think of spending the day at the beach. You are there to watch the sunrise. When the sun comes up in the morning, you have a long skinny shadow. As the morning goes on and the sun rises higher in the sky, you and your shadow are the same length. As noon approaches, when the sun is high above you, your shadow is short and stubby. Therefore, if you have an image that is long and skinny and the apex of the tooth root is missing, you've used too low of an angle, and you would need to increase the angle of the tube head if in sternal‑dorsal recumbency to shorten the image.