Ebook Feline dentistry (2/E): Part 2

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Part 2 book "Feline dentistry" includes content: Dental radiography, tooth resorption, oropharyngeal inflammation, oral masses, oral cavity trauma, occlusal disorders.

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Nội dung Text: Ebook Feline dentistry (2/E): Part 2

170 5 Dental Radiography Dental radiography plays an integral part in assessment of and prevention visit. The owner is advised to call the the dental patient. Intraoral imaging is indicated for evalu- office or come back at noon for discussion of dental ation of apparent pathology, as a way to monitor progres- examination and radiographic findings, while the animal sion or resolution of treated disease, and as part of the is still anesthetized. periodic professional oral assessment, treatment, and pre- ●● 9:30–10:30 a.m.: Preoperative laboratory tests, chest radi- vention visit. Intraoral radiography allows viewing of gross ographs (when indicated), and electrocardiographic pathology above and below the gingival margin and inside evaluation are performed. An intravenous catheter the tooth. It allows the veterinarian to gain needed infor- is placed. mation on tooth vitality, progression of pulpal pathology, ●● 10:30–11:45 a.m.: The patient is anesthetized, teeth are periodontal diseases, neoplasia, oral trauma, and anatomi- cleaned, the mouth is probed, charted, and oral survey cal orientation of the root structure before extraction. radiographs are obtained by the dental assistant. The vet- Postoperative imaging is also necessary to document com- erinarian performs a tooth- y- ooth exam and renders a b t plete extraction. diagnosis. A treatment plan is formulated by the veteri- narian and fees are calculated. 12:00 p.m.: The client calls. The veterinarian discusses 5 .1 Workflow – Incorporating Dental ●● examination findings, treatment plan, and fees while the Radiography into General Practice technician is completing the dental cleaning procedure. ●● 12:10 p.m.: After the treatment plan is approved, therapy When the patient is admitted to the hospital for oral evalu- begins, or a follow up appointment is made for the ation and care, the veterinarian cannot formulate an accu- needed therapy. rate treatment plan to share with the pet owner until a ●● 2:00 p.m.: Therapy is completed (time required depends thorough tooth- y- ooth assessment is conducted, includ- b t on procedure). ing visual examination, probing and full- outh intraoral m ●● 5:00–6:00 p.m.: The patient is discharged, with discharge radiographs (FMX) while under general anesthesia. orders and photographic report discussion with the owner. Anesthesia is necessary to immobilize the cat for intraoral film positioning and for protection of the patient, staff, and radiographic sensor. After the tooth- y- ooth exam has b t 5.1.1 Radiograph Equipment been performed and radiographs have been examined, a Digital intraoral imaging is a major technical advance in treatment plan can be formulated and discussed with the companion animal dental radiography. In place of film, an client for approval while the animal remains under anes- electronic sensor (digital radiography) or a phosphor plate thesia. Alternatively, the patient can be awakened after (computed radiography, CR) is placed against the teeth. teeth cleaning, irrigation, and polishing and treatment can The sensor or plate detects radiation and transfers the pat- be performed at a later date. tern to a computer screen as an image where it can be The following is a typical timeline for one patient (other enhanced, enlarged, electronically mailed, printed, or patients are added to the daily schedule depending on archived. Due to the advantage of digital imaging over film availability of anesthesia units and staff): including time and reduced expense as well as lack of ●● 9:00 a.m.: The patient is examined or if examined before- chemicals needed to process images, only intraoral digital hand, left for the professional oral assessment, treatment, imaging will be considered in this text. Feline Dentistry, Second Edition. Jan Bellows. © 2022 John Wiley & Sons, Inc. Published 2022 by John Wiley & Sons, Inc.
5. Workflow – Incorporating Dental Radiography into General Practice 171 To acquire diagnostic digital intraoral radiographs the tables (Figure 5.2a–b). Handheld units are convenient but veterinary practice needs: are not permitted in some states due to radiation safety regulations. 1) An X- ay generator that can be mounted on a table, r The position- ndicating device (PID) is an extension i wall, ceiling, rolling floor stand, or handheld. State reg- placed on the tube head at the collimator attachment. To ulations about which types of devices are allowed are minimize the amount of radiation exposure, the PID is available online. lead- ined. The shape of the PID may be circular or rectan- l 2) Digital sensor (DR) or phosphor plates (CR). gular. The PID is available in lengths from 4 to16 in. An 3) Computer and monitor. 8- n. extension (using a 4- n. cone) is referred to as short- i i cone technique; longer extensions result in a long- one c 5.1.2 X- ay Generator r technique. Exposure adjustments to accommodate differ- Skull films exposed using the whole- ody veterinary X- ay b r ent cone lengths employ the inverse square rule. For exam- generator are rarely diagnostic due to superimposition of ple, a 4- n. cone requires 1/4 of the exposure required by an i dental hard tissues (Figure 5.1a,b). Intraoral dental X- ay r 8- n. cone. Short- one technique, which produces less i c generators are offered as stationary, mobile floor, or hand- magnification, is generally preferable due to the fact that it held units. Stationary units can be wall, cabinet, or ceiling uses 1/4 of the exposure and is easier to position when mounted with long arms to extend to multiple treatment a a b b Figure 5.1 (a) Dental hard tissue superimposition in skull film resulting in a poorly diagnostic image compared to (b) Intraoral Figure 5.2 (a) Wall-mounted X-ray generator. Source: Image image in same cat demonstrating a mandibular oral mass courtesy Dentalaire. (b) Handheld X- ay generator, processor, and r consistent with osteomyelitis. monitor. Source: Image courtesy IM3.
172 5 Dental Radiography compared to the long- one technique. The long- one tech- c c nique, however, produces films with less divergence and scatter. Short cone produces more magnification and a wider penumbra compared to long- one technique. c The arm connects the X- ay tube head to the control r panel, which contains the timer, kilovoltage (kV), and/or milliamperage (mA) regulator. Most machines have a fixed kV (50–120) and mA (7–15). The only variable parameter is the duration of exposure in fractions of seconds or pulses. The timer is engaged only when the switch is depressed and automatically stops at the end of the preset exposure. The timer resets after each exposure. Most dental units use Figure 5.4 Size 1 and 2 DR sensors. Source: Courtesy of 110 V, 60 Hz, or 220 V/50 Hz AC electricity. A separate dedi- MIDMARK. cated electrical circuit is recommended. The kilovoltage peak (kVp) determines the penetrating power or quality of radiation produced. Kilovoltage (kV) Computed radiography (CR) systems involve the use of affects the contrast (shades of gray). The higher the kVp set- phosphor screens (plates), which are available in many ting, the greater is the photon energy that strikes an area. To sizes (Figure 5.5). After exposure, the screens are fed into penetrate larger teeth or more radiopaque surrounding struc- a scanner, which provides images on the computer moni- tures, higher kV is required to produce diagnostic images. tor within seconds after insertion. The phosphor screens Direct digital radiography (DR) sensors are commonly are exposed to bright light to erase the prior image and can connected via USB cable to a computer and placed in the be reused hundreds of times. CR systems are generally patient’s mouth similar to dental films. Images are viewed more expensive initially, but have advantages including in seconds and may be digitally manipulated to enhance being able to use larger #4, #5, and #6 films plus the ease details and minimize retakes. The DR sensors are the most of replacement films damaged due to bite trauma. The expensive part of the system, and although they are quite largest DR sensor size is #2. durable, care must be taken to prevent biting and water damage (Figures 5.3 and 5.4). ●● Rostral mandibles including the canines ●● Lateral obliques of the right and left maxillary canines ●● Right maxillary cheek teeth ●● Left maxillary cheek teeth ●● Lateral obliques of the right and left mandibular canines ●● Right mandibular cheek teeth ●● Left mandibular cheek teeth 5.1.3 Image Archiving Intraoral radiographs are examined as if the viewer is look- ing directly at the patient nose to nose; the patient’s left side is on the viewer’s right side, and the patient’s right side is on the viewer’s left side. All the radiographs in a single series should be labeled with the patient’s name and date of the study. Digital dis- play of full- outh survey images can be facilitated using m software templates supplied by the vendor. ●● The radiographs are arranged anatomically, maxillae above, mandibles below. ●● The patient’s right side should be placed on the left side of the template. ●● The maxillary radiographs are positioned with the Figure 5.3 Sensor bite damage. crowns of the teeth facing ventrally.
5. Radiation Safety 173 Figure 5.5 CR film sizes. Source: Courtesy of IM3. A full- outh (FMX) m radiographic series (Figure 5.6) consists of the Rostral maxillae including the canines. Full-mouth dental cat survey Right Left 108 mesial root seperation 107, 108, 109 Lateral-oblique view Rostral maxilla Lateral-oblique view Left maxilla 208 mesial root seperation right maxilla left maxilla 206, 207-209 104, 106, 107, 108 203, 204, 206, 207, 208 Figure 5.6 Full mouth intraoral radiograph series. ●● The mandibular radiographs are rotated until the coro- shields should be worn when exposing films unless the nal aspects of the teeth are directed dorsally. operator is at least 6 ft from the primary X- ay beam and r ●● The rostral maxillary and mandibular views are mounted tube head. In some states, the staff are required to leave the in the upper and lower center positions. room before X- ay exposure. r Two types of radiation apply to operator safety: primary and secondary. Primary radiation comes from direct expo- 5.1.4 Intraoral Radiograph Digital Software sure to the radiograph beam. The veterinarian or staff The software allows a variety of options for enhancing and member should never hold digital sensors in the patient’s manipulating the dental images for greater diagnostic mouth with bare or even gloved fingers. In order to avoid value (Table 5.1). The enhancements used most often finger exposure, phosphor plates or sensors are positioned include image enlargement, increased clarity, auto- in the mouth using external holding devices, wadded- p u contrast, grayscale resolution, spotlight features, inversion paper, or gauze. Secondary radiation comes from scatter, of black and white, and measurement rulers (Figure 5.7). which reflects from areas that have been irradiated by the primary beam. Protective devices must be worn for shielding. 5 .2 Radiation Safety 5.2.1 ALARA 5.2.2 Personnel Monitoring Radiation exposure should be “as low as reasonably achiev- Personnel radiation monitoring devices are required in able” (ALARA) to produce a diagnostically acceptable radi- most jurisdictions. A film badge service can be used to pro- ograph. Veterinary staff must be protected against excessive vide radiation monitoring for all staff members function- radiation exposure. Lead aprons, gloves, and thyroid ing near radiation exposure. The dosimeter badge should
174 5 Dental Radiography Table 5.1 Software study and image options 5 .3 Radiograph Image Troubleshooting Full mouth temp A way to acquire full mouth series. The 5.3.1 Foreshortened Image templates are customizable and stored Customized tool Great for post extraction radiographs or for The exposed dental image should approximate the size of clinics that may not be taking a full mouth the patient’s tooth. Foreshortened images, caused by exces- series on a particular patient sive vertical angulation, appear shorter than the patient’s Quick fire This gives the user an option to get into the anatomy. To correct a foreshortened image, the vertical software and begin acquiring images rapidly without tooth selection. angulation is reduced. Slideshow This option can be selected prior to feature acquisition or after acquisition to view images full screen and scroll to view by 5.3.2 Elongated Image selecting the right and left arrows Elongated images, caused by too little vertical angulation, Slideshow view This is what the images will look like as appear longer than the actual tooth. To correct an elon- they come up gated image, vertical angulation is increased. Template full This is how images will appear if the Dark image: overexposed from excessive exposure screen slideshow view is not selected prior to acquisition time or kV. Triadan label Upper left hand of image will have correct Light image: underexposed from too little exposure Triadan numbers for reference time or kV. Enhancing This tool bar is in the center of the main Blurred or double images are caused by movement of the toolbar screen and has options for enhancing and patient, sensor, X- ay generator, or by exposing a sensor r manipulation to user’s liking twice. Tongue movement in lightly sedated patients may Sharpen filter This enhancement sharpens the image to move the sensor during exposure. If the movement is con- allow more definition of anatomy tinued throughout the exposure, the image is blurred. If Invert This option will give the user a negative of the film were in one position for part of the exposure and the image then maintained in a second position for the remainder of Note to image Selection of notes will create a drop- own d the exposure a double image would result. text box for user to add notes which can be printed or hidden Annotations Tool allows user to create text, measure, mark, circle to highlight areas of concern 5 .4 Positioning to share with the client Template print Printable template for client take home There are various ways to position the patient (dorsal, ven- Print screen Ability to print digital pictures along with tral, lateral recumbent); the sensor; and the tube head to camera pictures obtain diagnostic intraoral images. See Table 5.2. The sen- sor or phosphor plate should be placed inside the mouth, as parallel as possible to the long axis of the tooth roots to be worn at all times in the veterinary office. It measures the be radiographed. Often this is not possible due to the oral amount and type of radiation an individual is exposed to in cavity anatomy. Operators must not use their fingers to the working environment. The badge should not be worn hold the sensor or plates during exposure. The sensor or outside the office. The periodic radiation monitoring report phosphor plate can be held in position by the endotracheal should be evaluated and saved indefinitely. tube, wadded- p newspaper, paper towel, gauze, hair u Table 5.2 Positioning. View Position Technique Maxillary incisors and canines Intraoral occlusal Bisecting angle Maxillary Intraoral and/or Bisecting angle premolars and molars extraoral Mandibular incisors Intraoral occlusal Lateral Bisecting angle Near parallel canines oblique Mandibular premolars and Intraoral Parallel molars
5. Positioning 175 a b Figure 5.7 (a–q) Examples of intraoral digital software screens. Source: Images courtesy of Midmark.
176 5 Dental Radiography c d Figure 5.7 (Continued)
5. Positioning 177 e f Figure 5.7 (Continued)
178 5 Dental Radiography g h Figure 5.7 (Continued)
5. Positioning 179 i j Figure 5.7 (Continued)
180 5 Dental Radiography k l Figure 5.7 (Continued)
5. Positioning 181 m n Figure 5.7 (Continued)
182 5 Dental Radiography o p Figure 5.7 (Continued)
5. Positioning 183 q Figure 5.7 (Continued)
184 5 Dental Radiography curler devices, lead radiograph gloves (without fingers inside), sponges, or clay encased in plastic bags. 5.4.1 Parallel and Bisecting Angle Techniques Parallel technique places the sensor or plate nearly parallel to the teeth to be imaged, with the radiograph beam posi- tioned at a right angle to the sensor or plate, creating a non- distorted image. Only the mandibular cheek teeth allow the sensor or plate to be placed lingually (parallel) in the intermandibular soft tissue parallel to the roots. The bisecting angle technique is used to facilitate intraoral imaging. Imaginary lines are drawn along the long axis of the teeth to be imaged and the plane of the sen- sor. The point where these two lines meet creates an angle. Instead of aiming the central beam perpendicular to the a sensor, as in the parallel technique, the central beam is aimed perpendicular to the imaginary line that evenly bisects the angle formed by the plane of the sensor or plate and the long axis of the tooth (Figures 5.8–5.10). The advantage of the bisecting angle technique is that it creates an image which approximates the size of the tooth itself. b Figure 5.9 (a) Parallel technique to expose the left cheek teeth in a cat. (b) Radiographs of left mandible revealing moderate periodontal disease as evidenced by horizontal bone loss. 5.4.2 Vertical and Horizontal Angulation a Vertical angulation refers to the up- nd- own movement a d of the PID. Vertical angulation determines how accurately the length of the object being radiographed is reproduced (Illustration 5.1). Horizontal angulation refers to rostral–caudal move- ments of the tube head. Proper horizontal angulation pro- duces normal interproximal anatomic representation of the teeth without overlapping. 5.4.3 Positioning for the Maxillary Arch Incisors: Face the sensor or plate toward the tube head b against the incisors and palate. In the normal- ized cat, s Figure 5.8 (a) Foreshortened image. (b) Elongated image. both canines should touch the sensor (Figure 5.11a– c). Be
5. Positioning 185 a a b b Figure 5.10 (a) Bisecting angle used to image the right maxillary cheek teeth in a cat. (b) Radiographic image of the right maxilla. careful not to compress the maxillae and mandibles in order to avoid damage to the sensor. Position the PID per- pendicular to an angle that bisects the film and canine teeth planes. Canines: Place the sensor facing the tube head, between the tongue and maxilla beneath the canine tooth root. Center the PID over the mesial root of the second maxillary premo- lar for dorsal or lateral oblique depending on the view needed. Determine the angle between the plane of the canine tooth root and the plane of the sensor/plate and then position the PID perpendicular to the bisected angle (Figure 5.12a,b). The lateral oblique view is recommended for close inspection of c the periapical region of the canine tooth. Premolars and molars: Place the sensor as close as possi- Figure 5.11 (a) Sensor placed in the cat’s mouth for exposure ble to the inner surface of the cheek teeth. Some veterinar- of maxillary incisors and canines. (b) Both canines touch the sensor. (c) Image created revealing external root resorption ians prefer to place the patient in lateral recumbency. This affecting both canines.
186 5 Dental Radiography 90° Parallel technique • Right mandibular cheek teeth • Left mandibular cheek teeth Sensor plate Long axis of tooth PID Bisected position angle Bisecting angle technique • Rostral maxilla including the canines • Rostral mandible including the canines • Lateral oblique of each maxillary canine Sensor plate Illustration 5.1 Parallel technique and bisecting angle technique. Illustration courtesy of Tama Rees, Veterinary Information Network. author prefers to position the patient in sternal recum- tube horizontally. Horizontal tube shift will separate the bency with a support placed under the chin, causing the superimposed roots on the film. The root that moves in an muzzle to be parallel to the tabletop. The sensor or plate is opposite direction from the horizontal shift of the tube is placed into the mouth. The PID is aimed at the roots of the buccal (or labial). In contrast, the root that moves in the premolars at approximately 45°. The maxillary fourth pre- same direction as the horizontal shift of the tube is lingual molar has three roots (mesiobuccal, mesiopalatal, and dis- (or palatal). When the tube head is moved rostrally, the tal). To avoid overlap of the mesiobuccal and mesiopalatal mesiopalatal root of the maxillary fourth premolar will be roots, put the PID in a caudal horizontally oblique position the most rostral root on the radiograph, and the mesiobuc- (Figure 5.13a,b). cal root will be caudal to the mesiopalatal root, positioned between the mesiobuccal and distal roots on the image. Another way to identify the three maxillary fourth pre- 5.4.4 SLOB Rule molar roots is by observing the parallax shift effect. When When two roots of a triple- ooted tooth (e.g. the mesial r exposed from distal to mesial the palatal root is in the mid- buccal and palatal of the maxillary fourth premolar) are dle. In the lateral projection, the palatal root is hidden superimposed on the radiograph, it is often difficult to dis- behind the mesiobuccal root. In the mesial to distal projec- tinguish the location of individual roots. Defining which tion, it is the mesiobuccal root that is in the middle. root is which is important when performing root canal therapy and in identifying pathology associated with 5.4.5 Extraoral Technique to Remove advanced periodontal disease. The SLOB rule (same lin- Superimposition of the Zygomatic Arch gual, opposite buccal), also called the buccal object rule, is a tube- hift technique that helps identify the relative buc- s Due to superimposition of the zygomatic arch over the colingual location of objects in the oral cavity. maxillary cheek teeth in cats, satisfactory views may not be To visualize the roots, two radiographs are taken at obtained using the standard bisecting angle technique. The oblique angles, fixing the vertical position and moving the extraoral technique will invert the right and left views of
5. Positioning 187 a a b Figure 5.13 (a) PID and sensor positioned to obtain image of the cat’s right maxillary premolars and molar. (b) Radiographic image of a cat’s right maxillary canine, second, third, and fourth b premolars and molar. Figure 5.12 (a) Lateral oblique positioning of the PID and sensor for a cat’s right maxillary canine image. (b) Image of the cat’s right maxillary canine and second premolar. perpendicular to the bisected angle of the film and tooth planes (Figure 5.15a–b). the patient, therefore software manipulation or image Canines: The mandibular canines can be exposed from annotation will be necessary to recognize which quadrant ventrodorsal (VD), dorsoventral (DV), or dorsolateral posi- is being examined. To avoid superimposition by the zygo- tions. For the dorsolateral view, place the patient in ventral matic arch, the sensor/phosphor plate is placed extraorally recumbency. Position the sensor between the tongue and and the PID is positioned rostrally oblique, aimed at the mandible, pushing the lingual frenulum caudally and posi- premolar roots just ventral to the zygomatic arch. The cusp tion the PID approximately 20° toward the canine tooth. In tips of the premolars should be near the lower edge of the some patients, there is insufficient space for the image- sensor. The sensor is placed extraorally and beneath the capture device between the tongue and mandible. In this maxilla and zygomatic arch (Figure 5.14a–c). case, the tongue can be placed between the teeth and image- apture device. c Premolars and molars: The mandibular cheek teeth are 5.4.6 Positioning for the Mandibles the only place in the cat’s mouths where true parallel posi- Place the patient in dorsal recumbency with support under tioning of the sensor can be achieved. Place the sensor on the neck so that the muzzle is parallel to the table top. the floor of the mouth lingual to the premolars. Gauze may Lateral recumbency can also be used. be used to help depress the film into the floor of the mouth. Incisors: Position the sensor toward the tube head against Aim the PID perpendicular to the tooth roots and film (par- the incisors and the lingual frenulum. Position the PID allel technique) (Figure 5.16a,b).
188 5 Dental Radiography Figure 5.14 (a) Zygomatic arch superimposed upon the left maxillary fourth premolar in a cat. (b) PID and phosphor plate position for extraoral image. (c) Extraoral image of the left maxillary premolars which virtually eliminates superimposition of the zygomatic arch. a b c
5. Positioning 189 a a b Figure 5.15 (a) Position of PID and sensor to expose the mandibular incisors and canines. (b) Imaged mandibular incisors and canine teeth in a cat, note tooth resorption affecting the mandibular canine roots. 5.4.7 Temporomandibular Joint The temporomandibular joint (TMJ), also called the crani- omandibular joint (CMJ), is a transversely elongated, syno- b vial joint formed by the condylar process of the mandible Figure 5.16 (a) Sensor parallel to the mandibular cheek teeth and the mandibular fossa of the temporal bone with PID positioned perpendicular to the sensor. (b) Left (Figure 5.17a–g). The retroarticular process is a caudoven- mandibular premolars. tral extension of the mandibular fossa, which partially envelops and prevents caudal luxation of the mandibular condyle. At the rostral margin of the mandibular fossa is a Extraoral TMJ technique includes closed- outhed DV/ m small, unnamed protuberance. VD, lateral, lateral oblique, and open- outhed views. The m The joint may be affected by congenital defects, trauma DV and lateral oblique techniques are preferred by the (luxation or fracture), infection (septic arthritis), degenera- author. For the DV exposure, the radiograph beam should tive joint disease, and neoplasia. Intraoral and extraoral be centered between the two TMJs with care to assure sym- techniques can be used to image the joint. metric positioning of the head. This is often difficult in The intraoral technique uses a number 0, 1, or 2 sensor or patients that have suffered head trauma. In those cases, VD phosphor plate, which is placed in the oropharynx wedged views may be easier to obtain. The normal TMJ space against the endotracheal tube in the area of the TMJ. The appears as a thin, sharply marginated, radiolucent band of PID is aimed at the ventral pinna against the ear canal. uniform width.