Figure 1. An incidental finding of a nonvital tooth (#102) as evidenced by an inappropriately wide canal. Nonvital teeth should be extracted or endodontically treated. I would like to take this opportunity to reiterate my firm admiration for an attainable imaging goal for your practice, namely the use of digital dental radiography. If you perform dental procedures in your practice, then you should consider incorporating it. A closer look Studies have shown dental radiographs reveal more pathology than thorough oral examination alone.1,2 Dental radiographs raise the bar diagnostically by allowing you to visualize the other half of the tooth that lies beneath the gingiva and bone. I may find a nonvital maxillary incisor tooth whose crown looks totally normal on visual inspection (Figure 1). In another patient, I may find a “missing tooth” that is actually unerupted and forming a dentigerous cyst beneath the gingiva. Dental radiography is essential for developing an individual treatment plan for each tooth in the mouth. The ability to obtain dental radiographs not only improves your diagnostic capabilities, it also can better your therapeutic outcomes. For example, supernumerary roots occur in approximately 10.3 percent of maxillary third premolars in cats.3 If you don’t perform dental radiography, you will not know you need to extract three roots instead of two (Figure 2). Tooth resorption in cats is another example. Without evaluating dental radiographs, you can’t determine which teeth are affected and devise the best treatment for each one. Avoiding unnecessary situations Figure 2. Tooth #207 in a cat shows radiographic evidence of having a third root, even though this tooth should typically have two. One example comes to mind. Years ago, an older cat presented through our emergency service with anorexia after extractions were performed at its primary care veterinarian’s practice a few days earlier. Oral examination revealed a dehisced extraction site of the right mandibular canine tooth (#404). After placing the patient under anesthesia, we performed dental radiographs (which were not done at the time of the extractions) that showed an iatrogenic fracture of the mandible in the area of an attempted extraction of tooth #404. Iatrogenic mandibular fracture is a tangible risk during mandibular canine extraction in cats, so it’s not uncommon for us to see this sequela as a specialist. This case has resonated in my mind all these years—if dental radiographs were taken at the time of initial treatment, the jaw fracture could have been avoided. Root replacement was so marked that the radiographic findings would have changed the course of treatment, and a crown amputation would have likely been chosen rather than an attempted extraction. If the primary care veterinarian had access to dental radiography, he/she would have known the resorption of the mandibular canine tooth was so advanced, there was no root to retrieve. Dental radiographs also allow you to determine if your dental treatment has accomplished its desired goal. A component of the American Animal Hospital Association (AAHA) dental guidelines, post-extraction radiographs are advisable not only to confirm complete tooth removal, but also to document it. Many practitioners tell me they never realized how many unexpected tooth roots remained after extractions until they started taking postoperative radiographs. A dental X-ray machine should be considered “standard equipment” for any practice doing extractions. Dental radiographs also are used to assess the long-term success of procedures (e.g. root canal therapy and periodontal therapy) by reevaluating radiographic appearance six to 12 months postoperative. I’ve told you this story previously, but it bears repeating. In 1997, when I was a new graduate venturing into general practice, my first employer bought a dental X-ray generator, as he knew I had an interest in dentistry. Dr. Bagley enjoyed buying new “toys” for his practice, though he realized many new pieces of equipment took time to pay for themselves, and some toys ultimately never did. Dr. Bagley was so impressed with how quickly the dental X-ray generator paid for itself that when demand for the service grew and a backlog of cases occurred at the dental X-ray unit, he purchased a second unit within a year. A dental X-ray machine tends to pay for itself rapidly, since it allows you to discover additional pathology that would otherwise go untreated. Many practitioners pursue a digital system for its ability to save time. Back in 1997, we used D-speed Kodak dental X-ray film and developed the film in a chairside darkroom. The process of developing archival-quality conventional dental X-ray films is laborious. Digital systems are more convenient, and if you are taking dental radiographs on every case, you will likely pay the extra money for the convenience factor of a direct or indirect digital system. Digital systems use less radiation than what is required to expose a conventional dental film. Digital models provide the benefit of reducing ongoing costs associated with film and processing chemicals, though software upgrades and customer support may negate these savings if not included in the initial purchase. Direct versus indirect digital systems At this point, a distinction should be made between direct and indirect digital systems. Direct digital radiography (DR) systems typically are attached directly to a computer via a cord. The immediacy of direct digital systems is a great benefit when learning positioning techniques. DR systems provide instant feedback, so if tube head positioning is elongated, the X-ray tube head can be adjusted quickly to see the benefit of repositioning. One disadvantage of a DR system is that sensor sizes are limited to a maximum sensor size “2.” This sensor is smaller than an entire canine tooth of many large-breed dogs. Commercially available direct digital size “4” sensors do not exist due to the expense to manufacture such a large sensor, coupled with a lack of demand in the human market for the size “4” sensor. Plastic sleeves are placed over the sensor to avoid damage from moisture, and care should be taken to prevent a patient from biting down on a sensor. A variety of direct digital systems exist for veterinarians, and it is worth looking at each type to ensure you are happy with the sensors and their individual software. Indirect systems (computed radiography [CR]) utilize reusable phosphor plates that are scanned to provide an image on the computer screen within seconds of exposing and scanning the plate. As the plates are fed into the machine, the image on the plate is scanned into the computer software, and cleared from the plate so it is ready to be used again. The plates are available in a variety of sizes, including size “4.” Phosphor plates can become scratched, so plastic covers are necessary to prevent damage and to avoid moisture and hair getting transported into the scanner. Meticulous care of the plates and the scanner are important to avoid artifacts on the images. Note the amount of radiation needed to provide an optimal image may vary when comparing new phosphor plates to those that have been reused many times. Phosphor plates are much less expensive to replace than a damaged direct digital sensor (approximately $100 versus thousands of dollars). I am often asked which type of system I use: DR or CR. My answer is both. I cannot adequately perform my job without being able to obtain high-quality dental radiographs, and therefore I like to have options. I often use a DR system with cats and small-breed dogs, and with cases where immediate feedback is beneficial to decrease treatment time, such as endodontic procedures. When evaluating a medium- or large-breed dog, I use the indirect CR to get a “big picture” assessment. If you are on the fence about whether a digital dental radiography system is right for your practice, as the sneaker ads say, “Just do it.” You’ll be glad you did. References 1 Verstraete FJ, Kass PH, Terpak CH. Diagnostic value of full-mouth radiography in dogs. American Journal of Veterinary Research 1998; 59(6): 686-691. 2 Verstraete FJ, Kass PH, Terpak CH. Diagnostic value of full-mouth radiography in cats. American Journal of Veterinary Research 1998; 59(6): 692-695. 3 Verstraete FJ, Terpak CH. Anatomical variations in the dentition of the domestic cat. Journal of Veterinary Dentistry 1997; 14(4): 137-40. 4 Blake WP, Micuda J, Hubbard JW. Use of dental films in veterinary practice. Journal of the American Veterinary Medical Association 1958 15; 133(4): 201-202.
