Intraoral Radiology

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Endodontic lesion typified
by periapical lucency at
root apex

Examining a dog's or cat's mouth has been compared to opening a Christmas gift, in that there is usually a surprise waiting, and unless you completely unwrap the present you will never find out what it is. Dental radiology allows the practitioner to further unwrap the mouth to "look inside" and examine the tooth as well as the supporting structures below the gum line.

At one time veterinary dentistry consisted of removing calculus from the crown. Now, cleaning the crown is only part of the dental prophylaxis, which also includes using a probe to measure periodontal pocket depths, charting abnormalities, polishing, and intraoral radiography.

When intraoral films should be used, is an individual decision. In general, any time the practitioner or staff notes a dental abnormality, or if there is unexplained bleeding, a radiograph is indicated. Common examples include evaluating the presence of unerupted teeth in show dogs (especially Dobermans, Rottweilers, and Giant Schnauzers all which require at least 40 teeth to be shown), bleeding, determining treatment options for periodontal disease, registering endodontic parameters including pretreatment, intraoperative and postoperative care, evaluating the extension of oral masses into the maxilla or mandible, and postoperative evaluation of extraction sites for root fragments.

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Normal-appearing bone support on
second premolar

Veterinary practitioners have the choice of using their stationary x-ray machine, a portable unit, or a human dental x-ray machine, The stationary unit should be set at a 12" to 16" film focal distance. Suggested technique used for cats and small dogs: 100ma, 50-70kvp, and 1/10 second. Human dental nonscreened film is commonly used and is less cumbersome than bulky standard veterinary film cassettes. Ultraspeed film sizes 0 ( 1/2" x 1"), 2 ( 1" x 2"), and 4 ( 2" x 4" ) adequately serve in most practice situations. Size 0 is especially useful for feline intraoral radiography. Ektaspeed film is twice as fast as ultraspeed. The trade-off is less detail with the Ektaspeed film.

Every intraoral film taken should include the full length of the tooth and at least 2 mm of the periapical bone. If there is pathology present, the entire lesion should register on the film together with normal bone.

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Sclerotic pulp chamber in the central
incisor secondary to pulpitis

Patient positioning is critical to avoid distortion. The ideal dental radiograph employs paralleling technique. The x-ray film is supported parallel to the long axis of the tooth, and the central x-ray beam is directed at right angles to the tooth and film. This method limits geometric distortion, in order to give an accurate representation of size and shape of the structures studied.

Anatomic configuration of the maxilla does not lend itself to use of the parallel film x-ray beam positioning method. The bisecting-angle technique is used here and in situations where the film cannot be placed parallel to the tooth surface. The x-ray beam is aimed at right angles to an imaginary line that bisects the angle made by the film and long axis of the tooth. Generally, a 45 degree angle from the plane of the hard palate is used in the maxilla. When radiographing the anterior mandible, in order to visualize roots of the incisors and canines, the central beam should be aimed at a 20 degree angle to the film plane.

There are several methods employed to develop intraoral films. Some veterinarians use regular hand tank chemicals and timing, others attach the films with photographic tape to a larger film and use the automatic processor. There are also automatic processors for dental films. An easier and faster (time to examination of diagnostic film -- 1 minute) method, is using rapid-process developing and fixing solutions in the darkroom, or using a Chairside Darkroom with the rapid-process chemicals. The Chairside Darkroom has an added advantage of a safety filter glass top which lets the practitioner develop the film at the dental operatory decreasing time spent walking to the hospital darkroom. The intraoral radiographs are immersed in the developer for ten to twenty seconds depending on the temperature and age of chemicals, then immersed in a water rinse, placed in the fixer for at least one minute, then rinsed once more in a new water solution. After examination, the film should sit for one hour to ensure adequate hardening of the emulsion for a permanent record.

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Conventional endodontics to repair
abcess secondary to tooth fracture

Intraoral radiology should be an integral part of every involved dental case in every animal hospital. The ease of using standard stationary veterinary radiograph machines, the ease or processing, and the great amount or information gained make the dental x-ray a win-win-win proposition.

 



This page last updated on October 31, 2000
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Jan Bellows, DVM
All Pets Dental Clinic
17100 Royal Palm Blvd.
Weston, FL 33326
(954) 349-5800
dentalvet@aol.com