Small Animal Dental Radiology
Author: Dr. James Anthony, DVM, BSc (Agr.), MRCVS, FAVD, DAVDC, DEVDC, PAg
Intra oral dental radiology is fundamental to the practice of veterinary dentistry. Radiographs show pathologic lesions or foreign bodies that cannot be identified in any other way and assist in the localization of these objects. Visualization is the key for successful dental treatment. Visualization can be accomplished by inspection (magnification loops and operating microscope), surgical exposure, or dental imaging (dental radiographs, MRI, CT). Radiology is as important if not more in dentistry as it is in other medical disciplines. Without dental radiography the operator is attempting to operate blindfolded. Oral radiology is comparable to having a boxed gift; you have an idea what’s in it, but until you open it you can’t be sure. Why is dental radiology important? It allows the operator to look beyond the obvious, it allows examination of the dentition and supportive structures, it allows for better treatment planning, and it allows for a more successful outcome. This results in a planned procedure without unexpected surprises, a healthier patient and a happier satisfied client.
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Dental radiographic images can help the operator identify tooth, bone, or soft tissue pathology. They help establish diagnosis, in treatment planning and in performing dental procedures. These images allow the operator to verify that the procedure(s) have been accurately performed and for documentation in the medical record for future follow up.
The indications for dental radiology are: periodontal disease, extractions, fractures, non vital pulps, resoptive lesions, missing dentition, orthodontic treatment, oral masses, endodontic therapy, oral abnormalities, and implantology to name a few. Radiographs are also an important part of the patients’ records. It justifies the reason for the procedure and documents the pathology as the information contained in a radiograph is not easily matched by written records. Radiographs are also much more indisputable than a written statement in the event of a disagreement or lawsuit. Communication with the client is facilitated by visualization of the pathology via radiographs.
Dental radiology can also be of benefit in non dental related areas such as: extremity evaluation of small animals, small exotics, nasal disease, and margin evaluation of post op hard tissue masses.
The best source of radiation is from a dental x-ray unit. These machines are compact, maneuverable, and have limited settings with low radiation exposure. The biggest benefit is that there is no patient transport. It is far easier to move the head of the dental x-ray unit than the animal. Most machines have settings in the range of 0.1-1.0 sec with 10 mA, 70 kvp and a focal distance of 20cm (for a standard x-ray unit). The cost ranges from $4,000-$8,000.00.
Due to the release of radiation, safety is of great concern. It is important to educate everyone in the hospital on radiation safety. The use of positioning devices or holders is encouraged. Always have individuals in the area protected with a lead barrier and away from the direct beam. Anyone using the radiographic unit should have radiation monitoring badges.
The use of intra oral film is key in successful dental radiography. There are a number of different sizes of films (sizes 0- 4). The most commonly used film sizes is number 2. The speed of film most commonly used is “D” (ranges from A-G). Each dental film contains an outer covering where the white portion faces the beam and the back has a tab to peel for developing. Next in the back is a lead foil to prevent scatter radiation. Then there is a folded black paper that folds over the film (dull green colour) to prevent light leakage. On the white portion of the outer covering of the film the operator will notice a raised dot which is by convention always to face the mid point of the mouth (area between the central incisors). This way the operator can identify which side of the face the film is showing.
Developing dental films can be accomplished via using existing dark room tanks, piggybacking the dental film on a standard film via an automatic processor, using a dental automatic processor, using self developing film, or by most commonly using a chair side developer. The chemicals can be evaluated via the use of step wedges. Film clips and drying racks will be required.
Digital radiographs are the next step in the evolutionary process of oral radiology and in my experience offers many more benefits than films. The advantages are numerous, some of them being: labeling and dating the images, receiving an image in seconds, the image can be enhanced and commented on, the operator can magnify the image, the radiographic image doesn’t degrade over time, the image can be enhanced with contract if too light or dark, radiation exposure is decreased 80% over D films, there is no chemical disposal, there are no storage issues (computer), pictures of the radiograph can be easily obtained to educate and give to the client and one can send the images electronically. Digital Radiography is an initial investment over film and you should be sure to have a good warranty program to cover your investment, and specifically, the digital sensor.
The operator can always use a standard radiographic unit, but is not recommended because of the fore mentioned reasons. The cost of time and frustrations of positioning and transport far outweigh its use for dentistry. There are two basic positioning techniques used in veterinary dental radiography
These positions are the parallel and bisecting angle technique. Dental radiographic interpretation is very important. The equipment necessary is some form of magnification, a view box, and a darkened room if film is used. If a digital system is used, knowledge of the program is essential to maximize the full benefits of the software. Evaluating dental radiographs is dependent on the operators’ knowledge of normal dental anatomy. The normal should be studied properly in order to understand pathological images. The operator needs to identify positional artifacts such as the middle mental foramen. Having a skull available will allow for easier study when looking at dental radiographs. Bottom line; know the normal anatomy. Remember to always correlate the images with the patient’s physical examination. The veterinarian should always interpret the radiographs to ensure proper treatment planning. For complete radiographic interpretation the material should be supplemented with a good oral pathology text or referred for a second opinion with a person with advanced knowledge in veterinary dentistry.
Dental radiography not only will benefit the patient but can also be a profit center for the hospital. Full mouth radiographs are recommended for all patients undergoing an oral hygiene procedure since studies have shown that 30-40% of oral pathology is missed with a comprehensive oral clinical examination; even under general anesthesia. Any tooth that is to be extracted should be radiographed to document the reason for extraction (would you repair a leg fracture without a radiograph? I feel it is a dis service to the patient and client not to take these radiographs when a tooth is extracted) and allow for proper treatment planning facilitating its extraction and a post-operative radiograph should be taken documenting its complete extraction. Just these two reasons will allow for a rapid ROI (return on investment) and pay off the software and equipment in less than a year. Investing in good veterinary dental radiographic equipment and software is an investment for the future improving the hospital bottom line but more importantly offering proper patient treatment resulting in a happier pet and client.