tips FoR MaSteRiNG FuLL MOuTH radiographs Kelly Vearil RVT, VTS (Dentistry) Learning Objective: After reading this article, the veterinary technician will be able to understand the indications of intraoral radiography and consider the implications of full mouth radiographs on every dental patient. The reader will become aware of five main intraoral views that comprise full mouth radiographs, and, using three simple rules, be able to troubleshoot the appropriate corrections. This program was reviewed and approved by the AAVSB race program for 1 hour of continuing education in jurisdictions which recognize AAVSB race approval. Please contact the AAVSB race program if you have any comments/concerns regarding this program s validity or relevancy to the veterinary profession.
In Veterinary Medicine we have been relying on radiographs as a valuable diagnostic tool for decades. According to the American Veterinary Dental College (AVDC), dental radiographs are one of the most important diagnostic tools available to a veterinary dentist. They allow the internal anatomy of the teeth, the roots and the bone that surrounds the roots, to be examined. 1 The indications for intraoral radiography are numerous. A few examples include retained root tip post extraction, fractured teeth, periodontal pockets, gum recession with or without root furcation exposure, missing teeth and tooth resorption. Teeth affected with tooth resorption need to be classified as Type I or Type II (whether or not there is the presence of a periodontal ligament space) to determine treatment options. 6 Radiographs are necessary in determining if full root extraction versus crown amputation is the indicated treatment. Fractured roots are also very common in teeth with resorption, making radiographs highly valuable prior to extraction. Even when teeth appear normal above the gum line radiographs can still be useful. In fact, a study conducted at UC Davis with 226 dogs and 115 cats with no clinical pathology revealed up to 41.7% pathology when radiographs were performed. 8,9 Standard of Care There are numerous practices that have adopted the AAHA protocol of full mouth radiographs on every patient. This recommendation is outlined in the Revised AAHA Dental Care Guidelines for Cats and Dogs, 2013. It states, Radiographs are necessary for accurate evaluation lower 2nd premolars root tip is cut off on the size 2 sensor. Whether learning on a digital system or film, one way to make learning positioning easier is to perform the views in the same order each time. Research has According to the American Veterinary Dental College (AVDC), dental radiographs are one of the most important diagnostic tools available to a veterinary dentist. and diagnosis. 5 In addition, AAHA standards (November 1, 2013) require AAHA practices to provide intubation and general anesthesia for all dental procedures. 5 This standard is supported by both the American College of Veterinary Anesthesia and Analgesia and the AVDC. 3 Set a Goal For many practitioners, the quick full mouth radiographs is a misnomer. The need for quality radiographs is balanced by the length of anesthesia. For example, it is realistic to set a goal to achieve a 15 minute set of radiographs on a small to medium sized dog (20 minutes for a large dog), but it ends up taking closer to 30 minutes or longer due to shooting and reshooting to get a diagnostic radiograph. For the feline patient, a 10 minute full mouth series is a realistic goal, but the zygomatic arch interferes and the shown that repetition allows the brain to learn the information more quickly. When first starting out, it is best to purchase a set of real skulls and/or cadavers and set aside quality (quiet) time at the clinic to practice. equipment All that is required to produce intraoral radiographs is radiographic generating equipment (RGE), and either a digital sensor/software system or analog film, and a method for developing and viewing the radiographs. A number of units are commercially available offering a variety of features; this section will cover the basic principles. RGE The intraoral x-ray generator is made up of a generator, a tubehead and a control unit. They often have a set KVP and ma; the seconds are variable.
3 Simple Rules There are also three simple rules to keep in mind when learning to achieve each view successfully. This will help reproduce the same diagnostic image each time. 1 if the image is foreshortened, move the tubehead toward the tooth root angle. 2 if the image is elongated, move the tubehead toward the sensor or film angle. 3 if you cut the image off at the edge of the beam (cone cut), move the tubehead toward the area of cone cut. 4 Steps for Success 1 Position the patient 2 Position the film/sensor Control Unit The control unit and interface usually consist of a way to select the appropriate exposure (tooth) and some control focal distance, as well. Tubehead The x-ray beam exits through the x-ray tube and is also known as a position-indicating device (PID) which exits through a long hollow tube, or cone. In general, the tubehead focal distance should be as close to the patient as possible as to lessen scatter radiation. 7 Analog Film There are typically three common sizes of intraoral film used in veterinary medicine: 0, 2 and 4. The self-contained film is flexible and features multiple layers, making it light proof and water-proof. Film and the Developing Process Chair-side or darkroom developing are options; the chairside developer allows fast developing without leaving the dental operatory and may be the most practical. (fig1) The requirements for using film are a set of rapid developing chemicals such as Rinn 4, four cups large enough for a size 4 film containing Developer, Water, Fixer, Water, and either a dark room or the chair-side developer. The film is swirled in the rapid developer for 10-40 seconds (or until an image begins to become visible), then rinsed in the water, then placed in the fixer for twice as long as the developer (or until the film turns from green to black) and finally rinsed again in water. Developing times are dependent on temperature, the warmer the chemicals, the quicker the developing times. It is recommended that a final rinse be performed using tap water to remove all silver emulsions prior to drying. Otherwise the films will be spotty when they dry. Digital System There are currently two options for digital systems, CR and DR. With CR there is a 3 Angle the tubehead (horizontally and vertically) 4 Center (the tubehead over the film/sensor) phosphor film that is processed and then transports the information to a digital image. DR or direct is a wired sensor which transfers the image directly to a computer. Currently size 0 and 2 are the only available sensor sizes, 2 being the most widely used in small animals. (fig 2) Size 0 may be useful in exotic or pocket pet views. Most software systems will arrange the teeth in the correct format for viewing. Diagnostic radiographs A true radiographic representation of the tooth ideally involves the crown and root. For accurate diagnosis, the Veterinarian should be able to see the entire apex of the root and surrounding bone. The importance of including the crown is detecting endodontic pathology within the pulpal horns or crown trauma involving the pulp. 2 When proper technique is used the shadows of the root(s) are projected onto the film or sensor without any elongation or foreshortening. Positioning the Patient Position the patient the same way each time. This will help achieve a level of consistency. For example, in dorsoventral views, props are utilized to align the maxilla parallel with the tabletop. (fig 3) Positioning the Film or Sensor Always check film or sensor placement each time. Props are utilized to maintain its position. When using analog film, it is important to know how to utilize the correct orientation for taking and viewing radiographs. The technician should keep the position of the film consistent throughout. The convex dots on films are to be facing the tubehead and toward the coronal, not the apical surfaces of the teeth being radiographed. Knowing this, when viewing films, it is accurate to have the raised (convex) dot facing the viewerviewer and the concave side away from the viewer. When using this convention, it is easy to determine which side of the patient is being viewed: when viewing the premolar and molar teeth, if the rostral teeth are on the viewer s right it is the patient s right side, conversely if the rostral teeth are on the left it is the patient s left side. When viewing incisors and canines: it is the same as viewing a V/D abdominal radiograph the right side of the mouth will be on the left, the left side of the mouth is on the right.
Maxillary teeth are viewed with the roots up. Mandibular teeth are viewed with the roots down. When using a digital sensor, proper placement is with the cusps of the crowns to be radiographed at the edge of the sensor. There will be a frame, and it is important to have the crowns positioned within this frame, as anything outside will not accept an image. The Tubehead The tubehead moves on two axes, horizontal (side-to-side, lateral to the patient) and vertical (up-and-down, dorsal-ventral to the patient). The end of the tubehead is typically round where the radiation is projected and contains lines and/or v notches indicating the center of the tubehead. Props (Positioning Aids) Modeling clay helps to prevent the sensor/film from falling out of place; when placed on the side opposite of the tubehead, it is very effective. It can be molded and cut to form to any area of the mouth. If a piece of an exam glove or plastic wrap is placed around it, it can be used over and over again each time without contamination. Paper towel or gauze can also be helpful aids in holding the film/sensor in place. Five Main Views There are five main views for positioning full mouth radiographs in the veterinary Full Mouth Radiograph Figures Figure 1 Chairside Developer Figure 2 From left to right: Size 4, Size 2, Size 0 Figure 3 Preparing patient for dorsoventral positioning. rolled towel placed under chin. Maxilla is parallel to the table. Figure 4 Proper positioning for maxillary incisors. Figure 5 Proper positioning for the lateral maxillary canine. Figure 6 Proper positioning for imaging the maxillary premolars. Figure 7 Step one position of tubehead pointing at teeth to be radiographed (top). Figure 8 Step one showing the bisecting angle. Always check film or sensor placement each time. Props are utilized to maintain its position. Figure 9 Patient positioned for imaging the mandibular incisors and canines. Figure 10 Patient positioned for mandibular left premolars and molar. rostral view in canine species is performed the same way. Figure 11 Patient is positioned for the caudal mandibular premolars and molars.
Rostral View The anatomy of the rostral mandible is narrow and will prevent the film/sensor from achieving a true paralpatient. For larger patients, there may be multiple views necessary to complete the series on each side. Once completed, repeat the same views on the opposite side. All 6 incisors on one view for cats and small to medium dogs At an obliqued horizontal angle to prevent first premolar overlapping the canine Two views with a #2 sensor for cats/small dogs. Cats/small dogs on one view Maxillary incisors Begin with the patient in ventral recumbency; a rolled towel is placed under the chin to make the maxilla (the palate) parallel to the table top. The film/sensor is placed parallel to the palate with the cusps of the incisors just at the edge and including all six incisors. (For large dog breeds this will require two views.) Begin with the tubehead pointing at the sensor then tip caudally 10 degrees. Your vertical axis will be ~80 degrees assuming the film/sensor is at 90 degrees and parallel to the table top. Check to ensure the tubehead is centered over the incisor teeth. The centering line (guide) should be even with the philtrum of the nose at midline. (fig 4) Lateral Maxillary Canine Keep the patient in ventral recumbency as in the maxillary incisors view. Film/sensor is parallel to the palate and with the cusp of the canine tooth at the corner edge. The vertical angle of the tubehead is directed at the angle halfway between the long axis of the roots and the film/sensor (at approximately 80 degrees) and the beam centered over the midline. (fig 5) Then, the horizontal angle of the tubehead is tilted laterally (obliqued) approximately 20 degrees in a caudo-rostral direction. This horizontal tilt prevents superimposition of the maxillary first premolar teeth. Re-center the tubehead over the canine tooth once it has been obliqued. Maxillary Premolars/Molars The positioning is exactly as maxillary incisors and canines with the patient in ventral recumbency and the maxilla parallel to the table. Film/sensor is parallel to the palate and with the cusps of the premolar teeth just at the edge. (fig 6) Two or more views are required to include all maxillary premolars and molar teeth. The vertical angle of the tubehead is directed halfway between the long axis of the tooth roots and the film/sensor; this is approximately 45 degrees. The film/sensor is centered over the premolar and molar teeth. In cats and brachycephalic species, the anatomy of the maxilla is rounded and thus the exact angle required to reproduce an accurate image of the maxillary premolars (the bisecting angle) is equal to the plane of the zygomatic arch of the maxilla. (fig 7) The result is superimposition of these teeth and the zygomatic arch. There are two different variations on this view that the author offers to correct this problem: Near Parallel Variation for Cats/Brachycephalic The patient is positioned in lateral recumbency with the teeth to be radiographed positioned away from the table. The film/sensor is placed diagonally in the mouth from one edge against the palatal surface of the table side and the other rests on the edge against the lingual surface of the up side. To position, start by directing the tubehead at the premolar teeth to be radiographed then move the tubehead, approximately 20 degrees over the top of the head. Be sure to center all of the teeth. Decreased Angle Variation for Cats/Brachycephalic The patient is positioned in ventral recumbency. A rolled towel is placed below the chin to keep the palate parallel to the table. The film/sensor is parallel to the palate and with the cusps of the premolar teeth just at the edge. Start by splitting the difference to find the vertical angle halfway between the long axis of the tooth root and the film/sensor (the bisecting angle). (fig 8) Then direct the vertical angle of the tubehead toward the tooth roots by decreasing the angle by ~20 degrees. Example: Begin at 55 degrees on the tubehead and then lower to 35 degrees. This will purposefully elongate the roots past the zygomatic arch. Mandibular incisors and Canines The patient is placed in dorsal recumbency with a rolled towel placed under the neck so that the jaw of the mandible is parallel with the table. Positioning is exactly as Maxillary incisor except the patient s recumbency is flipped. The film/sensor is placed parallel to the mandible with the cusps of the incisors at the edge. The tubehead is directed at the film/sensor and then tipped ~10 degrees caudally. Center the tubehead over all the incisor teeth. (fig 9) On small dogs and cats, all six incisors and both canine teeth can be achieved on the same view. Multiple views are required for larger dogs. Mandibular Premolars and Molars Rostral view Caudal parallel view
lel position to the root apices. For positioning a radiograph for the rostral mandibular premolars and molars, begin by positioning the patient in ventral recumbency with a rolled towel under the neck so that the mandible is parallel to the table. The film/sensor is positioned in the mouth parallel to the mandible. The tubehead is directed at a vertical angle that is halfway between the tooth roots and the film/sensor (the bisecting angle). Center the tubehead over the premolar teeth. There are multiple views required for the canine species. Mandibular canines can be often achieved in the same position just rostral to the first premolar in dogs. This is the only view required for the mandibular two premolars and molar in cats. (fig 10) Caudal Parallel View In the medium or large dog species the anatomy of the caudal mandible will allow you to achieve parallel placement of the film/sensor to the tooth roots. The patient is in lateral recumbency and just like a radiograph of an abdomen, the portion to be radiographed and the film/sensor are parallel to each other. The tubehead is directed at both the mandibular caudal premolars and molars and the film/sensor. (fig 11) References 1. American Veterinary Dental College http://www.avdc.org/ radiographs.html 2. Bird L, Dental radiology in Perrone J. et al., Small Animal Dental Procedures for Technicians and Nurses, (iowa: John Wiley & Sons, inc. 2013), 87-101 3. Davis S., Spencer K. et al., AAHA announces new mandatory dental standard requiring anesthesia, intubation NewStat (Aug 28 2013) 4. Dentsply international rinn PA 17405-0872, usa 5. Holmstrom Se. et al., AAHA Dental Care Guidelines for Dogs and Cats Journal of American Animal Hospital Association (Mar/ Apr 2013): 49:2 6. Lobprise H, intraoral radiology in Blackwell s Five Minute Veterinary Consult: Clinical Companion: Small Animal Dentistry. (iowa: Blackwell Publishing Professionals, 2007), 26-50 7. Mulligan T, Aller M, Williams C et al. Atlas of Canine and Feline Dental radiography: Yardley, Pennsylvania: Veterinary Learning Systems; 1998 8. Verstraete FJ., Kass PH., Terpak CH. Diagnostic Value of Full-Mouth radiography in Dogs American Journal of Veterinary research (June 1998): 59(6):686-91 9.Source Department of Surgical and radiological Sciences, School of Veterinary Medicine, university of California, Davis 95616, usa 10. Verstraete FJ., Kass PH., Terpak CH. Diagnostic Value of Full-Mouth radiography in Cats American Journal of Veterinary research (June1998): 59(6):692-5 CONTINUING EDUCATION QuiZ OnLinE visit VetMedteam.com and log in with your Vet Med Team Profile. Kelly Vearil, RVT, VTS (Dentistry) Kelly has been a registered Veterinary Technician since 1997. She is an instructor for the Veterinary Technology Program at the University of Cincinnati where she instructs students in dentistry and dental radiography. Her love of dentistry has brought her through the credential process for the AVDT where she passed her exam to become VTS Dentistry in 2014. Her future goals are to inspire students by setting a good example in her profession and community through continuing education. She loves to share her knowledge of dentistry at any opportunity.