All small animal practitioners routinely take radiographs of patients where indicated. Radiographs simply put, help the veterinarian evaluate the patient.
In a study conducted at the University of California, Davis ( Am J Vet Res 1998, 59, pgs. 686-691 and 692-695), where all dogs and cats presented for dental cleanings were radiographed, significant lesions requiring therapy were uncovered in a majority of the cases. Currently, less than 10 percent of practices use dental radiology to help their patients. This low percentage is due to many factors including set up expense, inexperience with radiographic technique and processing as well as inexperience with film interpretation.
Figure 1: Dental radiographic units allow for use on the operatory table.
What are the advantages, equipment needed and techniques used to expose and process dental films?
Advantages of taking dental radiographs are many:
- Viewing pathology below the gingiva and inside the tooth documenting the presence of lesions to support treatment decisions.
- Evaluating an area where the teeth are not clinically apparent for root fragments.
- Determining the cause of chronic nasal discharge.
- Evaluating tooth vitality
- Evaluating the number of permanent teeth present in a puppy or kitten as part of a detailed soundness examination before the secondary teeth erupt. Some breeds must have a minimum number of teeth to be accepted in the show ring.
- Anatomical orientation and documentation of root structure before extraction.
- Evaluation after extraction to confirm all root fragments were removed.
- Pre-operative evaluation of gross tumor margins to help plan surgery.
- Treatment planning evaluation when periodontal disease is present (gingival bleeding on probing, tooth mobility, gingival recession, furcation exposure, increased probing depths).
- Evaluating feline odontoclastic resorptive lesions (FORLs).
- Evaluating jaw fractures.
- Evaluating oral and facial swellings.
- Evaluating pre-operative, intra-operative and post-operative endodontic treatment.
The radiographic unit
A conventional radiograph unit can expose quality films using 100 ma 10 mas technique at 40(cat)-60 (large dog) Kv, with a film focal distance of 16-in. While the veterinarian does not need to own a dedicated dental unit, it makes the process more efficient.
Figure 2: There are three film speeds: D, E, F.
There are great advantages in owning a dental radiograph unit: most dental units cost between $3,000-$5,000; shorter film focal length and automatic collimation result in less scattered radiation and exposure to the patient; extension arms of various lengths allow vertical, horizontal, and rotational movement resulting in less patient repositioning; and radiographs can be obtained on the dental operatory table rather than moving the patient to a radiography area (Figure 1).
The efficiency which a film (Figure 2) responds to X-ray exposure is known as film sensitivity or speed. The three film speeds are:
Figure 3: Dental film sizes
- D speed (Ultraspeed, Kodak) provides high contrast and fine detail. Ultraspeed is the most popular film used in veterinary dentistry.
- E speed (Ektaspeed, Kodak) requires 25 percent less exposure time, compared to D speed film, with minimal loss of contrast.
- F speed (InSight, Kodak) requires 60 percent less exposure time than D speed film, and 20 percent less than E speed film.
Exposure example for a typical 20-pound dog using a dental radiograph unit is 55kVp, 10 mA: Ultraspeed 0.40 sec, Ektaspeed 0.30 sec, InSight 0.16 sec.
Figure 4: EVA digital dental sensor and holster (AFP Imaging).
Four sizes of dental film are used (Figure 3, p. 12S):
- Child periapical (size 0) measures 7¼8 x 15¼8 inches. Size 0 is used mostly in cats, exotics and small dogs.
- Adult bitewing (size 2) measures 11¼4 x 15¼8 inches and is the most commonly used size in veterinary dentistry. Size 2 fits into 35 mm slide mounts for use in presentations.
- Bitewing (size 3) film measures 11¼16 by 21¼8 inches. Size 3 films adapt well to the mandibular cheek teeth.
- Occlusal (size 4) film measures 21¼4 by 3 inches. Occlusal film is used to radiograph large breeds.
Digital dental radiology uses a sensor rather than film. The image captured on the sensor is displayed on a computer screen. (Figure 4, p. 12S).
Figure 5: Positioning for incisor images.
A radiographic dental survey consists of a minimum of eight views:
- Rostral maxilla
- Lateral left canine
- Lateral right canine
- Rostral mandible
- Right maxillary cheek (premolars and molars) teeth.
- Left maxillary cheek teeth
- Right mandibular cheek teeth
- Left mandibular cheek teeth