Dentistry and Oral Surgery

OCCLUSION

Occlusion refers to the spatial relationship of teeth within the mouth. Malocclusion refers to the situation when teeth or jaws are not correctly aligned. Although cosmetic issues of misaligned teeth are not typically a concern in dogs and cats, malocclusions can result in discomfort from impingement of teeth on soft tissue structures of the opposing dental arcade. Dogs and cats with a normal occlusion have a scissors bite, where the incisors come together to closely overlap like blades of a scissors (Figure 32-5, A, B). When teeth are properly aligned in scissors occlusion, there is maximal function of all teeth with no occlusal trauma. Variations of dental occlusion in dogs and cats occur depending on the breed and skull type. The relationship of brachyodont teeth in normal occlusion is discussed later.

EXTRAORAL EXAMINATION

The examination begins with extraoral observation of the head, face, eyes, ears, and neck using direct visual observation, palpation, and smell. Using both hands, palpate each side of the face, head, and neck for symmetrical comparison. Feel the temporal and masseter muscles for the presence of atrophy, enlargement, or pain. Palpate the ventral, lateral, and medial surface of the left and right mandibles for the presence of swelling that could be evidence of neoplasia or fracture. Small-breed dogs with advanced periodontal disease are commonly affected by bone loss and pathologic fracture of the mandible, which may be found as an incidental finding in the examination room.

Visually inspect the ears and note evidence of discharge, odor or pain on palpation because middle ear disease may be a cause for the presenting complaint of pain on opening the mouth. Visually inspect the eyes and palpate using your thumbs on the closed eyelids to gently push (retropulse) both eyes at the same time. Bilateral retropulsion allows for symmetrical comparison of depth and firmness (Figure 32-8). Often if a space-occupying mass (as a result of neoplasia, inflammation, or infection) is present behind or beneath the eye, retropulsion may find a decreased ability of the globe to move caudally in the orbit on one side when compared with the opposite side. Ability to retropulse varies depending on facial conformation. Retropulsion of the eyes of brachycephalic dogs and cats results in less movement of the globe, so comparison of both eyes is important to determine relative differences. Observe for evidence of ocular discharge, which may be due to blockage of the nasolacrimal duct by a pathologic process, such as a tooth root abscess or neoplasia. Palpate the soft tissue in the area ventral to the medial canthus of the eye. Swelling in this area may be due to a tooth root abscess of the maxillary fourth premolar. Evaluation of the neck includes palpation of the right and left mandibular salivary glands beneath the skin of the ventral neck. The mandibular salivary gland is the only easily palpable major salivary gland in dogs and cats. The three other major salivary glands are either too diffuse to palpate easily (parotid, sublingual glands) or are not superficial enough to palpate (zygomatic gland). The mandibular gland is easily distinguished from the mandibular lymph nodes because it is softer, larger than, and caudomedial to the mandibular lymph nodes. Once the salivary glands are located, the mandibular lymph nodes can be identified by moving the finger tips cranially. Palpate the lymph nodes bilaterally for symmetry and firmness. In the cat, mandibular lymph nodes are difficult to palpate unless they are enlarged. In the dog, mandibular lymph nodes are almost always palpable, ranging in size from 0.5 to 1.5 cm in diameter depending on the size of the patient. Although we often refer to the mandibular lymph “node,” in reality, the area contains anywhere from one to five nodes. Other nodes that drain the head (retropharyngeal, parotid) are not normally palpable. Nine percent of dogs have another lymph node that is palpable in the subcutaneous tissue dorsal to the maxillary third premolar tooth. This node is referred to as the facial or buccal lymph node and is often bilateral, when present.

The occlusion should be evaluated before intubation by noting any teeth that are positioned incorrectly. The technician should pay particular attention to discrepancies of jaw length, the spatial relationship of the teeth as they erupt, and to the relationship of the erupting teeth with the soft tissues of the opposing jaw. Note any deciduous teeth that have not exfoliated by the time their permanent counterpart has erupted because persistent deciduous teeth may create situations of periodontal disease and redirection of permanent tooth eruption. Once the deciduous and permanent canines begin to erupt, routinely monitor the relationship of the mandibular canines and the space between the maxillary third incisor and canine teeth. Deviations from normal canine positioning can cause trauma to the palate and require treatment.

INTRAORAL EXAMINATION

The intraoral examination consists of evaluations of the soft tissues of the oral cavity, the dental structures, and the periodontium, a term that describes the supporting structures of the teeth. A standard approach to the oral examination allows for efficiency and thoroughness. Begin by observing the skin and mucosa of the upper and lower lips. Some breeds are prone to lip fold dermatitis of the lip area caudal to the mandibular canine tooth that can cause oral malodor unrelated to periodontal disease. Buccal mucosa refers to the mucosa that begins at the mucocutaneous junction and lines the cheeks and lips. Alveolar mucosa refers to the mucosa that lies against the bone of the upper or lower jaw, which meets with the gingiva at the mucogingival junction. The normal appearance of the mucosa may be pink or pigmented, and the mucosa should exhibit no lesions, ulcerations, or swellings. Pay particular attention to areas of mucosa that lay adjacent to periodontally diseased teeth because the bacteria in the plaque may contribute to painful mucosal ulcerations, often referred to as chronic ulcerative paradental stomatitis (CUPS) (Figure 32-9). Observe the caudal cheek lining in the region of the carnassial and molar teeth. This mucosa frequently becomes pressed between the teeth during chewing, creating a condition known as “cheek chewing lesions” (Figure 32-10). Similarly, mucosa beneath the tongue may also show signs of chewing lesions referred to as “tongue chewing lesions,” which are usually bilateral (Figure 32-11). These lesions usually do not require treatment unless the lesions are not bilaterally similar or if the lesions are ulcerated. In these cases, the affected mucosa may be removed and submitted for histopathologic evaluation.

Two raised bumps are found on the alveolar mucosa dorsal to the maxillary fourth premolar and first molar teeth. Salivary secretions from the parotid and zygomatic salivary glands travel through ducts leading to these duct openings (Figure 32-12).

The roof of the mouth is composed of the hard and soft palate. The hard palate forms the rostral two thirds and is covered by palatal mucosa arranged in prominent ridges, called rugae (Figure 32-13). These rugae range from eight to ten in number. In brachycephalic dogs, the rugae are closely positioned, and hair and debris can accumulate in these rugal folds. On the midline of the hard palate, just caudal to the incisor teeth, the incisive papilla is a round, slightly raised structure (Figure 32-14). Lateral to the incisive papilla, a small bilateral communication with the incisive duct and vomeronasal organ exist. The vomeronasal organ is a sensory organ involved in detection of pheromones and other chemical compounds. Palpation of the area lateral to the incisive papilla may normally feel as if there is air trapped beneath the mucosa as a result of the communication between the mouth and these nasal structures. The soft palate consists of mucosa and muscle that separate the oropharynx and nasopharynx. Two prominent bony structures can be palpated just lateral to the midline of the soft palate that are the hamular processes of the bilateral pterygoid bones. If one or both hamular processes are difficult to palpate, this may be due to the presence of a nasopharyngeal mass.

The pharynx should be evaluated for evidence of inflammation or neoplasia. When the patient’s mouth is open, bilateral folds of pharyngeal mucosa will be evident lateral to the tongue. These are referred to as the palatoglossal folds, and this area and the mucosa lateral to these folds may be inflamed in cats with lymphocytic-plasmacytic stomatitis (LPS) (Figure 32-15).

Gently hold the tip of the tongue to enable visual examination of the dorsal, ventral, and lateral surfaces. Lift the tongue to observe the mucosa of the floor of the mouth and the base of the tongue. In the awake patient, the examiner’s thumb may be used extraorally to push the tongue dorsally for better visualization of the ventral surface of the tongue. The dorsal surface of the tongue is covered by thousands of papillae, some of which contain taste buds. The large, distinctive papillae located at the caudal third of the tongue are the vallate papillae, which are spaced in a curved line separating the body from the root of the tongue. Depress the tongue to visualize the tonsils, noting any enlargement or change in color or texture. The color of a normal tonsil is typically more hyperemic than the color of the adjacent mucosa. Normal tonsils may be fully contained within the tonsillar crypt and may be difficult to visualize.

During the soft tissue examination, any tissue variations from normal should be described by recording the size, shape, color, surface texture, and consistency (e.g., soft, firm, hard, or fluctuant). A dedicated area on the dental record may be created to allow for documentation of any abnormalities of oral soft tissue structures (see Figures 32-6, A and 32-7, A).

The next step in the intraoral examination is evaluation of the teeth and their supporting structures. First, determine the presence or absence of teeth in each quadrant. Missing teeth can be documented on the dental chart by darkening or circling the missing tooth. Further radiographic evaluation of areas of missing teeth is imperative because dentigerous cysts can develop as a result of an unerupted tooth. To evaluate the condition of the teeth and periodontium, the technician must use a periodontal probe and dental explorer. These dental instruments are important clinical tools for obtaining data about the health status of each tooth. Consider the canine mouth as containing 42 patients and the feline mouth containing 30 patients, each patient requiring a thorough evaluation. The periodontal probe has a handle with a round or flat rectangular working end that is marked in millimeter increments, ending in a blunt tip. The probe is used like a miniature intraoral ruler to measure attachment levels, sulcus and pocket depths, loss of bone in furcation areas, and size of oral lesions. It is also used to assess the mobility of teeth and the presence of gingival bleeding. Periodontal probes are available in an assortment of design styles, with variations in thickness of the diameter of the working end and variations in increments of millimeter markings (Figure 32-16). Probes with Williams’ markings have millimeter increments at 1, 2, 3, 5, 7, 8, 9, and 10 mm. The UNC 15 probe has millimeter markings at 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, and 15 mm, which is useful for large dogs or patients with deep periodontal pockets. Some probes have a small 0.5-mm ball on the end to minimize tissue trauma; however, these probes typically have markings at 3.5, 5.5, 8.5, and 11.5 mm, resulting in inexact determination of pocket depth. Although many probes exist, a probe with markings beginning at 1 mm is necessary for assessing subtle pocket depths in cats. The Michigan “O” probe with Williams’ markings is best suited for use in cats because the working end of the probe is the narrowest in diameter. Some styles contain color-coded bands for easier viewing of calibrations. A Naber’s probe is a curved furcation probe that is used to assess the extent of bone loss in the furcation area.

The dental explorer has a slender, wirelike working end that tapers to a sharp point and is used to explore the topography of the tooth surface. When the explorer is held with a light modified pen grasp, the technician will acquire a tactile sense to locate tooth surface irregularities, such as caries, feline resorption, calculus deposits, and pulp exposure. Tactile sensitivity is achieved when the flexible working end of the explorer vibrates as it detects surface irregularities. The vibrations are transmitted from the tip to the handle as felt by the technician. The explorer is also used to determine the completeness of treatment following calculus débridement and to ensure smooth transitions of dental restoratives (fillings). Several designs of explorers are available (Figure 32-17). Varying degrees of flexibility contribute to the degrees of tactile sensitivity. The shepherd’s hook is the most common explorer in most veterinary practices and is often paired with a periodontal probe as a double-ended instrument. Although it is convenient to have on the opposite end of a probe, it is bulky, inflexible, and less adaptable to subgingival use when compared with other explorers. The Orban explorer has a 2-mm tip that is bent at a 90-degree angle from the shank, allowing it to be used subgingivally with little tissue distention (stretching of the gingiva away from the tooth) or trauma to the epithelial lining of the sulcus. The 2-mm tip may be a limitation when using the Orban to determine depth of a dental lesion, such as caries or feline resorption. The curved 11/12 ODU explorer is an ideal choice for veterinary use. The curvature of the long shank and working ends make it adaptable to use on rostral and caudal teeth, supragingivally and subgingivally, and its smaller working end allows for detection of subtle hard tissue defects.

Periodontal instruments, including the probe and explorer, are held with a modified pen grasp (Figure 32-18), which is a variation of the grasp used for writing. This recommended grasp facilitates good fingertip tactile sensitivity and precise control of the instrument’s working end, decreasing risk of trauma to the tissues. The modified pen grasp uses three fingertips placed in a triangular (tripod) position, plus a rest finger. The pads of the index finger and thumb rest on the instrument where the handle and shank meet to hold the instrument. The pad near the fingernail of the middle finger rests on the shank. The shank is the portion of the instrument that connects the handle with the working end (Figure 32-19). Proper placement of the middle fingertip pad against the shank is important for enhancing tactile sensitivity and helping to guide and control the working end. The ring finger should rest on an oral structure, such as a tooth located close to the working area, to provide stability of the hand for added control. Keeping the ring finger in contact with the middle finger will ensure proper wrist motion by limiting the amount of finger motion and will prevent finger fatigue. The little finger should be relaxed and has no specific function in this grasp.

The assessment of the periodontium and teeth should begin at the midline of the mouth and systematically evaluate each tooth, one at a time, by using both visual observation and tactile use of the probe and explorer. Begin detecting excessive tooth mobility by placing the tip of the probe against the tip of the tooth and gently attempting to move the tooth in a buccolingual direction. Movement is estimated on a scale of 1, 2, or 3, based on the number of millimeters beyond normal physiologic mobility the tooth moves in one direction (Box 32-3). A slight amount of movement is normal as a result of the periodontal ligament that connects the tooth to alveolar bone. The most severe mobility, a classification of 3, includes any tooth with vertical movement. As each tooth is approached to check for mobility, visually notice the characteristics of the gingiva for color, shape, texture, and consistency. Healthy gingival tissues are pink (except where normally pigmented), stippled (orange peel appearance), firm, tapered to a thin margin, and scalloped to follow the contour of the cementoenamel junction (CEJ) and underlying alveolar bone. Any area of the gingiva that deviates from these normal characteristics should be examined closer by use of the probe.

The probe is gently inserted into the sulcus or pocket, ensuring that the probe is kept as close to parallel to the long axis of the root as possible, with the side of the probe tip in contact with the tooth. When physical resistance is felt at the base of the sulcus or pocket, note the marking level on the probe that is adjacent to the gingival margin. The probe is then “walked” around the tooth using up and down bobbing strokes approximately 1 to 2 mm in height (↕) and in 1- to 2-mm horizontal steps (↔) to assess the entire circumference of the tooth (Figure 32-20). Abnormal measurements (those greater than 3 mm in dogs, greater than 1 mm in cats) should be noted on the dental chart along with the specific location of the pocket measurement (i.e., MB for mesiobuccal). Probe measurements between millimeter markings are rounded up to the larger measurement. For accurate readings, it is essential for the technician to develop skills in consistent probing forces (between 10 to 20 g of pressure). This pressure amount can be practiced by pressing the probe tip into the pad of a thumb until the skin is depressed approximately 2 mm.

In areas where the height of the free gingival margin has migrated apically toward or beyond the CEJ, the probe is used to measure gingival recession. Recession is measured in millimeters from the CEJ to the level of the gingival margin. Attachment loss is a term that more truly describes the periodontal state of a tooth because it accounts for both pocket depth and gingival recession (Figure 32-21). Gingival hyperplasia occurs when the free gingival margin migrates coronally, toward the crown of the tooth. Hyperplasia is measured in millimeters from the bottom of the sulcus to the gingival margin, which is covering a portion of the tooth crown. An increased pocket depth may be due to hyperplasia or attachment loss, so clinical examination findings are necessary to determine if the increased probing depth is due to a true pocket or a pseudopocket.

When approaching multirooted teeth, the probe is used to assess loss of bone in the areas between and around the roots. A bifurcation is the furcation between two-rooted teeth and should be assessed from the buccal and lingual-palatal surfaces. Trifurcations of three-rooted teeth should be assessed between each of the three roots. The extent of bone loss determines the furcation classification (Box 32-4). A Naber’s furcation probe is curved to fit over the dental bulge of the crown so that the side of the tip can be held as parallel as possible to the long axis of the tooth. The tip is dragged horizontally across a root, dipping into the furcation area and continuing to the adjacent root. The depth of penetration into the furcation area determines the classification. If a straight probe is used, care must be taken to minimize tissue distention.

During the periodontal evaluation of each tooth, also observe the hard structures of the tooth and use the dental explorer when noticing any chips, fractures, pulp exposure, or abnormal wear patterns of abrasion or attrition. Abrasion refers to tooth wear associated with aggressive chewing on external objects, such as toys, rocks, and ice cubes. Attrition refers to two possible scenarios. Physiologic attrition refers to the normal wear associated with tooth-to-tooth contact of a patient over time with normal mastication. Pathologic attrition is caused by a malocclusion resulting in abnormal wear of teeth as a result of contact with teeth of the opposing jaw.

Dental caries (commonly referred to by the lay term of “cavities”) result from demineralization of the enamel and dentin from acids produced by certain oral bacteria. These lesions occur most commonly on occlusal (flat) surfaces of the molar teeth. Gently explore for pits and fissures of the occlusal surfaces of the maxillary first and second molars and the distal half of the mandibular first molar, feeling for areas of demineralization. Use the explorer to check for clinical signs of feline resorptive lesions by dragging the sharp point horizontally across the cervical portion of each tooth. Sometimes it is challenging to determine whether a concavity in the area of a furcation is a resorptive lesion or merely mild furcation exposure. If a resorptive lesion is present, the explorer tip will “catch” on the edge of the concavity, whereas the explorer will freely move out of the concave area as easily as it fell into it when encountering mild furcation exposure. When tooth fractures are present, gently drag the sharp point of the explorer across the tooth surface, feeling for any openings into the pulp. Teeth with significant abrasion may have a brown or black dot in the center of the worn tooth. This can be a sign of either chronic pulp exposure or a reparative material produced by the tooth in response to chronic wear (tertiary dentin). Pulp exposure can be distinguished from tertiary dentin by use of an explorer. If a tooth has pulp exposure, the tip of the explorer will “fall into a hole,” whereas a discolored area caused by tertiary dentin will feel smooth as glass when the explorer is run over this area. This is an important clinical distinction because treatment of pulp-exposed teeth is necessary, but worn teeth with tertiary dentin usually do not require treatment (Figure 32-22, A, B).

EQUIPMENT

The dental x-ray machine may be wall mounted, or it may stand on the floor with wheels that permit storage when not in use. The unit is composed of three primary parts, the control panel, a long (72- to 86-inch) arm that extends from the control panel, and a tube head that is attached to the end of the arm (Figure 32-23). The control panel, typically mounted to a wall near the dental workstation, contains the power switch, selector buttons for kilovoltage and milliamperes, a dial or buttons for changing exposure time, and a button that is located at the end of a 6-foot coiled cord. Many dental x-ray units have an internally set level of kilovoltage and milliamperes, and only exposure time may be changed for a darker or lighter technique. The timing selection may also be located at the end of the cord of some newer models. An indicator light and an audible sound are emitted from the control panel when exposure is made.

The milliamperage (mA) setting regulates the intensity of the electric current that heats the filament (cathode), thus controlling the quantity of electrons produced and available to bombard the target (anode). Milliampere seconds (mAs) describes the quantity of radiation, which is the milliamperes multiplied by the exposure time. For example, a film exposed for ½ second at 10 mA would be an exposure of 5 mAs.

The peak kilovoltage (kVp) is a measure of electric force that regulates the speed at which the electrons travel between the negatively charged cathode (filament) and the positively charged anode (target), thus controlling the quality of the x-ray beam. When the electrons hit the anode at a higher force, x-rays produced have a greater penetrating power at the surface of the skin. Most dental machines operate at 60 or 70 kVp. Low kilovoltage settings result in images with high black-white contrast, useful in detecting caries or resorption. High kilovoltage settings result in low contrast with a wider gray scale between the black-white densities, which is useful in monitoring periodontal disease.

The cathode and anode are housed in the Coolidge tube located in the tube head at the end of the articulating arm. Within the tube head, the Coolidge tube is immersed in oil to help absorb the heat produced at the target. The position-indicating device (PID) contains a collimator that controls the beam size. Varying from 8 to 16 inches in length, the PID extends from the tube head to the patient’s mouth and aids in minimizing scattered radiation.

The timer switch starts the production of the x-rays. Timers may be calibrated in fractions of seconds or numbers of impulses. Once the timer is activated, a short delay occurs while the filament is preheating. With experienced use of the radiograph machine, the technician will be able to determine proper exposure times based on the size of the patient and the density of the tissues through which the x-ray beam must penetrate. It is helpful to create an exposure time chart to post near the control panel for quick reference. New machine models marketed for veterinary use provide timers with preset exposure times associated with pictures of the dental arcade. The technician only needs to select the dog or cat, patient size, and specific tooth.

All veterinary staff must become familiar with radiation safety guidelines. The timer switch can be remotely wired and mounted outside of the dental treatment room or at least 6 to 8 feet away from the tube head. Standing at a distance behind a barrier or at a 90-degree to 130-degree angle that is perpendicular to the beam will place the technician at a safe position away from the direction of the beam. The film should never be held in the patient’s mouth by the technician while the radiograph is taken; therefore anesthesia is necessary not only to ensure diagnostic quality films, but also for safety reasons. Make certain that the machine is inspected regularly for leakage by a competent radiation expert, as may be required by state regulations. Development of skills will minimize unnecessary radiation from retakes resulting from poor technique or positioning.

FILM

Intraoral film consists of a plastic base covered on both sides with emulsion of silver halide crystals. The film is wrapped in black paper with a lead foil backing placed on the side that will be farthest from the beam. The lead foil prevents scatter radiation from affecting the back side of the film. The film, paper, and foil are wrapped in either a plastic or paper packet. This type of film is considered direct exposure or nonscreen film. The white surface of the film wrapper should always be placed in the mouth so that it faces the beam, and the colored surface of the film wrapper is placed away from the beam. A raised (convex) dot is present on the white surface of the film wrapper, and a recessed (concave) dot is present on the colored surface (Figure 32-24, A, B). The raised dot will always be placed so that it faces the beam, and the concave dot will be farthest from the beam.

Dental film is available in several sizes, ranging from 0 to 4, and to accommodate variation in sizes of veterinary patients, it is important to keep all sizes of film in stock (Figure 32-25, A, B). Intraoral film also comes in several speeds. The speed refers to the sensitivity to radiation exposure, or the amount of radiation required to produce the image. Less radiation is required to produce an image using fast film; however, faster film, such as E-speed, contains larger silver halide crystals; thus appearance of the image is grainier than that of D-speed. Very slow speed films (speeds A, B, C) are associated with higher radiation exposure and are no longer used. Current choices include D-, E-, and F-speed film. Recent advances in F-speed film has allowed for reduction in radiation requirements up to 60% compared with D-speed film while maintaining good image quality. Film is sensitive to heat and moisture and should be stored in a dry, clean, cool place. Observe time limits printed on the boxes and discard the film when expired. The contents of a dental film packet are shown in Figure 32-26, C.

FILM PROCESSING

To convert the latent image into a visual image, the film is processed using chemicals that convert the silver halide crystals to metallic silver and preserve the image. Processing intraoral film can be accomplished in a dark room, a manual chairside developer (Figure 32-26, A), or an automatic processor.

Use of the chairside developer allows for rapid evaluation of radiographs following approximately 1 minute of processing time. Premixed chemicals (developer and fixer) are available from veterinary distributors. The developer box contains a light filtering window for viewing and hand portals with sleeves that keep light from entering. An orange filtering lid is used with D-speed film, whereas a red lid is used with E- and F-speed film. The films are opened inside the chairside developer and attached to a film clip. Inside, there are four cups into which the film will be dipped. Working from left to right, the first cup is filled with developer solution. The second cup contains water for rinsing. The third cup contains fixer solution that will halt the development process, wash off the silver halide crystals that were not exposed to radiation, and preserve the image on the film. The fourth cup contains water for rinsing (Figure 32-26, B). Films must be developed from left to right without backtracking to prevent contamination of the solutions. One exception is that films in the fourth cup may be placed back into the third cup (fixer) without a problem. The timing of each step is critical, and manufacturers’ directions should be followed. Keep in mind the possible need for adjustments in time when the temperatures of the chemicals are not the optimal 68° F. Following fixation, the films should be rinsed in slowly running water for 20 minutes before hung on a film rack to dry. Once completely dry, films can be placed into film mounts or small coin envelopes to be filed with the patient’s dental record.

Automatic processors used for standard x-ray films may be used to develop dental films by taping the dental film to the back end of a standard film and having it tag along with the larger film. This process is sometimes unreliable because it may cause the dental film to get lost or stuck in the rollers of the processor.

DIGITAL RADIOGRAPHY

Use of computed digital radiography (CDR) in the veterinary practice is increasing in favor as practitioners become more aware of the benefits when compared with conventional radiographic techniques. The quality of the digital images is improving since its first introduction in dentistry, and today the resolution is good, but still does not approximate that of nonscreen film. Direct method CDR technology, most commonly used today, uses an electronic intraoral sensor, a computer, and the x-ray machine. The sensor, called a charged coupled device (CCD), is either cordless or attached to a cord that connects to the computer. After covering the sensor with a plastic infection barrier, the sensor is placed into the mouth to capture the image and convert it to the digital format of “pixels,” picture elements in various shades of gray. A remote module transmits the data to the computer for the image to be immediately viewed, manipulated, and stored. The images can be magnified, and enhancements in contrast or darkness can be made. The sensors are available in sizes comparable with traditional dental film sizes 0, 1, and 2, limiting application in large-breed dogs that typically require size 4 films to view the entire tooth image. Because using a size 2 sensor for larger mouths requires more exposures to accomplish the task, it is practical to use standard radiography for some patients and digital radiography for other patients. When using digital technology, caution must be used to ensure that patients have adequate anesthesia depths because replacement of a damaged sensor is costly.

Digital technology reduces radiation exposure by 50% to 90% when compared with use of D- and E-speed film. Most modern dental x-ray machines are compatible with digital radiology if they have timers that allow the exposure setting in of a second time frame. A disadvantage of digital radiography is the high initial cost of the sensor and software. However, the expense is offset by the cost of film and processing chemicals.

EXPOSURE AND PROCESSING ERRORS

Errors in film exposure and processing account for unnecessary radiation exposure and additional anesthetic time for the patient. Cone cutting occurs when the beam misses portions of the film, resulting in clear areas of the film. Elongation and foreshortening (stretched and shortened images, respectively) are caused by inaccurate vertical angulation during PID alignment (Figure 32-27, A-C). Images that are too dark or too light can result from errors in kVp and mA settings or in exposure and processing times. If the film is placed in the mouth with the wrong surface facing the beam, dotted streaks from the lead foil will appear across the film surface. Care must be taken when placing multiple films into the fixer cup, ensuring that each film is placed parallel to the adjacent film to prevent scratches that appear as white lines when emulsion is removed from the film surface.

TECHNIQUES

Three techniques are commonly used to obtain dental radiographs. Each technique will consider the relationship of the beam to the film and tooth or area to be imaged. The proper-sized film is placed into the mouth and held in position with gauze. The paralleling technique requires the film to be placed parallel to the long axis of the tooth. The beam is then directed at a right angle to the film and teeth and positioned to aim for the center of the film (Figure 32-28). Parallelism can only be used on the mandibular teeth, caudal to the second premolars, where the film can easily slide toward the floor of the mouth.

The symphysis at the rostral portion of the mandible and the flat palate of the maxilla prevent the use of the paralleling technique. To minimize inherent distortion of dental structures where the paralleling technique is not an option, the bisecting angle technique is used. The x-ray beam is projected at a right angle to an imaginary line that cuts in half (bisects) the angle formed by the plane of the film and the long axis of the tooth (Figure 32-29).

The occlusal technique places the film on the occlusal plane and directs the beam at a right angle to the film (Figure 32-30). Typically, this view is of value in showing larger areas on one film, with applications to view nasal disease and also for identifying root remnants.

RADIOGRAPHIC INTERPRETATION

To assess the presence of intraoral pathologic conditions on radiographs, it is essential to have knowledge of the appearance of normal radiographic anatomic structures (Figure 32-31). The radiodensity of the components of the teeth and supporting structures varies widely; therefore the terms radiopaque and radiolucent are used to describe the relative radiographic appearance of oral and dental structures. Radiopaque structures, such as cementum, dentin, and bone block or absorb the radiation, causing that portion of the processed radiograph to appear light or white. The enamel covering of the crown is the most radiodense structure of the tooth. The lamina dura, which is a cribriform plate of bone lining the tooth socket, appears as a white line adjacent to the periodontal space surrounding a healthy tooth. Beyond the lamina dura, the trabecular pattern of bone may vary in radiodensity. The cortex of the mandible is radiodense.

In contrast, radiolucent structures, such as the soft tissue and periodontal ligament space, appear dark or black because the x-ray photons can easily pass through to the film. The periodontal ligament fibers are not visible on the film; however, the space they occupy can be traced as a black line surrounding the roots. Because pulp is soft tissue, it also appears as a dark area (less radiodense) in the center of the tooth.

The radiolucent mandibular canal lies apical to most of the mandibular tooth roots. In small-breed dogs, the apices of the mandibular first molar roots may be seen at a level of or even below the mandibular canal, extending into the ventral cortex. Normal anatomic structures must be distinguished from pathologic structures. For example, the middle mental foramen is located apical to the mandibular second premolar in dogs and can be misinterpreted as a periapical pathologic condition if superimposed over a tooth root (Figure 32-32). It is helpful to have a textbook with normal and pathologic radiographic appearances to refer to (see Recommended Reading).

SONIC SCALER

The sonic scaler is powered from an air compressor on a dental unit and is attached to the low-speed air line. It operates with a frequency between 2000 and 9000 cps. The tip vibrates in an elliptical pattern, with all surfaces around the diameter of the tip active. The vibrations are audible to the human ear creating a sound that may be uncomfortable to some operators. As a result of the low frequency, the sonic scaler has less ability to remove heavy, tenacious calculus and is slow to accomplish its task. It is best suited for use in cats or dogs with light accumulations.

ULTRASONIC SCALER

Ultrasonic devices use electrical energy that converts the working tip to mechanical energy in the form of rapid vibrations to effectively remove biofilm and calculus deposits. Ranging in frequency from 18,000 to 50,000 cps, above the audible human range, they are more popular and practical for veterinary use than the sonic scaler. The ultrasonic scaling unit contains the electronic generator inside plastic housing. A hose connects the unit to the water supply, either a portable pressure tank or a quick disconnect at the sink pipes. A cable attaches the unit to a foot pedal, and the handpiece is attached by tubing that transports the water for coolant. A power cord is also attached. Unlike hand scalers that only remove debris with direct contact, the ultrasonics also have the benefit of the stream of water coming from the tip that acts as a coolant and lavage, flushing debris from the sulcus. The flushing action is destructive to the biofilm by causing acoustic turbulence and cavitation. Acoustic turbulence, also known as acoustic microstreaming, is the disruption of the bacteria in plaque caused by the streaming of the fluid over the tooth surface or the churning of the fluid within the confined pocket space. Cavitation is the energy that is created from the mist of water. As the water coolant exits the handpiece and strikes the vibrating working end, it creates thousands of water bubbles. As the bubbles in the mist implode, enough energy is created to disrupt the bacterial cell walls.

SAFETY PRECAUTIONS

Because water is a necessary part of the dental cleaning, appropriate safety precautions must be taken for the technician and the patient. To reduce the amount of aerosolized bacteria, the mouth can be rinsed with chlorhexidine (0.1% to 0.2%) before scaling. This preemptive rinse will also reduce the severity of bacteremia of the patient, which invariably occurs during a dental cleaning. The technician and any co-workers in the vicinity of the workstation should wear gloves, masks capable of high bacterial filtration, and eye protection, such as plastic goggles or disposable face shields. The patient’s eyes should be lubricated and covered to protect against debris and contaminated fluid from entering. The single most important safety precaution when using ultrasonic scaling lavage is to intubate the patient and check to ensure that the endotracheal cuff is fully inflated. The airtight seal of the cuff should be checked occasionally to prevent the patient from developing aspiration pneumonia. However, care should be taken to avoid excessive inflation of the cuff that may result in a tracheal tear or necrosis. Placement of a radiopaque laparotomy sponge in the back of the throat before scaling will filter the loosened debris; however, remembering to remove the sponge after scaling is critical.

TIP DESIGNS

The tip designs have improved since the early 1990s, with more design options currently available. Standard-sized “universal” and broad tips are designed for removing medium and heavy deposits, whereas the slim tip designs provide for better access to subgingival pockets and furcation areas. Approximately 30% to 40% more narrow than standard tips, the slim tips are approximately 0.5 mm in diameter at the blunt end and designed to mimic periodontal probes. The slim profile enables easier access to the base of deeper pockets and improves tactility for better detection of calculus. They are available in straight and curved designs. Precision tips are available in diameters as narrow as 0.2 mm at the tip for use in advanced periodontal procedures. These are extremely fragile and must be used with a light touch. Another tip option is the diamond-coated tip. If used incorrectly during a nonsurgical procedure, the diamond coating can cause soft tissue damage and excessive loss of tooth substance; therefore this design should be reserved for use during open-flap procedures and only used by highly skilled clinicians. A new design offers a tip with a built-in LED light (Figure 32-37). The LED technology tends to offer only minimal additional light when used with a good surgical overhead light. A new tip designed for use in furcations has a 0.8-mm ball on the end that may be too large to access the furcations of some animal’s teeth.

Tips should be replaced at least annually or when they are bent or worn down (Figure 32-38). As the tip wears, it becomes shorter and the effectiveness of scaling diminishes. One ultrasonic manufacturer offers a wear indicator that helps to measure the amount of wearing of the tip. For each millimeter of wearing, there is a 25% decrease in efficiency.

ENERGY DISPERSION

For effective scaling during use of hand instrumentation, the sharp cutting edge of the working end must contact the calculus. In contrast, there is ultrasonic energy dispersion over a 360-degree circle around the tip of power instruments. The vibrating activity occurs on the back, face (concave surface), two side (lateral) surfaces, and on the point; however, each surface has varying degrees of vibrations, depending on the type of scaler used. Typically the strongest vibrations are concentrated 2 to 4 mm from the tip. Technicians must know the specific type of unit that they are working with and understand the differences in levels of energy dispersal among different tip surfaces to correctly adapt the tip to the tooth for efficient scaling.

TYPES OF ULTRASONIC SCALERS

Ultrasonic scalers are available in two types, magnetostrictive and piezoelectric, each distinct in their mechanism of action, type of transducer, and direction of tip movement. The transducer is the portion of the handpiece that converts electrical energy into mechanical energy.

The magnetostrictive scaler is the most common type of power scaler used in human and veterinary dentistry. The typical magnetostrictive unit has an insert that slides into the handpiece. The insert has two connected parts, the transducer and the working end. The magnetostrictive transducer is a stack of thin nickel alloy metal strips. When a magnetic field is created from the copper coil inside the handpiece, the dimension of the strips is altered by lengthening and shortening, thus sending vibrations to the tip.

Movement of the tip is in an elliptical pattern with the energy dispersion around the entire diameter of the tip, providing vibrations on all surfaces. The point of the tip can cause damage when directed at a 90-degree angle to the tooth, acting like a jackhammer on hard dental tissue (Figure 32-39). The face (concave surface) is the usable portion of the tip that has the most powerful vibrations, followed by the back. The two side surfaces have the least vibrations. The back and side surfaces are used for the majority of scaling. Magnetostrictive units range in frequency from 18,000 to 42,000 cps (18 to 42 kHz). Another type of magnetostrictive scaler uses a transducer that is a ferrite rod to produce a rotational tip movement. Differences in operation between magnetostrictive units require close attention to manufacturer’s recommendations. See Box 32-6 for preparation guidelines for a magnetostrictive unit with a metal stack transducer.

The piezoelectric scaler uses either ceramic disks or crystals as the transducer to produce the straight, linear movement of the tip. Electrical energy causes the disks to alter dimension by expanding and contracting, sending the vibrations to the tip at a frequency ranging from 25 to 50 kHz. Because of the back-and-forth motion, the tip is only active on the two lateral surfaces, forcing the operator to pivot the wrist as the tip is moved around the tooth. If the other surfaces are accidentally adapted to the tooth, the operator will be warned by a different sound and incomplete removal of debris. The limitations of effective vibrating surfaces cause the piezoelectric scaler to be more technique sensitive than other power scalers. The transducer’s ceramic disk is fragile and easily breakable if the handpiece is accidentally dropped.

KNOB SETTINGS

The power knob adjusts the amplitude, the distance the tip is moving back and forth in one cycle. Greater distance is higher power. Higher power is necessary to remove heavy deposits, whereas low power is satisfactory for removing plaque. It is good principal to use the lowest power setting that will accomplish the task. Low power should always be used with thin tips to prevent the tips from breaking.

The water knob adjusts the water flow through the handpiece. Because the ultrasonics produce heat, there must be adequate fluid to prevent pulp damage caused by heat during scaling. Pressure of the water supply line to the unit must be a minimum of 25 psi. A warm or hot handpiece is an indication that the water pressure is inadequate, and the clinician must immediately stop and make adjustments by increasing the water amount and checking the water pressure (if a portable water tank is used). With magnetostrictive units, the water knob should be turned until the water exits the tip as a mist, rather than just a straight stream. Water on the piezoelectric unit should be adjusted to a steady drip.

SUPRAGINGIVAL INSTRUMENTS

Sickle scalers are the instruments used to scale the crowns of the teeth. The flat face may be either straight or curved lengthwise; the straight lateral surfaces are flat and converge to form a pointed back and tip. When envisioning the cross section of a sickle, the instrument is characteristically triangular in shape with 70-degree to 80-degree internal angles between the face and lateral surfaces (Figure 32-43, A). The sharp tip will cause lacerations if the instrument is used subgingivally; however, it may be used with caution slightly below the gingival margin where the gingiva is spongy and loose enough to permit insertion. Because the sickle is a universal instrument, either cutting edge may be used depending on how the handle is tipped. Owing to the straight side surfaces, the sickle is not conducive to following the curved contours of roots and is therefore reserved for coronal scaling.

When the handle, shank, and blade are on the same plane, the instrument is designed for use toward the front of the mouth. For caudal teeth, the shank will be angled and the instrument will be double ended to provide mirror images. This style is useful for veterinary patients during scaling of the buccal groove of maxillary carnassial teeth. One working end is contoured for scaling the mesial edge of the groove, and the contralateral end contours with the distal edge of the groove.

When placing the blade against the tooth, the face should be at an angle between 45 degrees and 90 degrees with the tooth surface. The cutting edge is directed to the apical edge of the calculus, lateral pressure is placed against the tooth, and the instrument is used with a short pull stroke to disengage the debris.

SUBGINGIVAL CURETTES

Curettes may be used for supragingival scaling, though they are designed for subgingival scaling and root planing. The flat face is curved lengthwise from the heel to the toe, meeting the lateral surfaces to create a cutting edge that extends around the toe. Unlike the flat lateral sides of the sickle scaler that converged to form a pointed back, the sides of the curette are rounded, creating a round back that is easier to insert into a sulcus or pocket. The cross section of the curette is classically shaped like a semicircle with internal angles of 70 degrees to 80 degrees between the face and lateral surfaces (Figure 32-43, B).

A universal curette can be adapted for all surfaces of the teeth, whereas use of an area-specific curette would require several different instruments to scale each tooth in the mouth. Use of area-specific instruments is an advanced concept and should be used only by technicians having an understanding of the inherent design features and thorough knowledge of root anatomy and shape. When an area-specific instrument is used incorrectly, it can cause gouging of the root surface and trauma to the adjacent soft tissues.

The terms site specific and area specific are often interchanged with Gracey instruments, though other area-specific instruments exist. Dr. Clayton Gracey designed curettes in the 1930s to be used as a set, each instrument having a complex curvature of the shank for better access to the specific teeth. Unlike the universal curette that is only curved on the plane of the face, the Gracey is also curved on the plane of the lateral surface. To help identify the two curved planes, hold the instrument with the terminal shank perpendicular to the floor and view the face at eye level. The face will slope downward, rather than parallel with the floor and perpendicular to the terminal shank, and the lateral surfaces will be curved to the left or right. This curvature enables adaptation around the contours of roots. As with universal curettes, site-specific curettes have two cutting edges; however, the site specific is unique in that only one edge is designed for use. Before adapting the blade to the tooth, the technician must confirm that the appropriate edge is chosen. To determine the correct cutting edge, hold the terminal shank perpendicular to the floor to view the honed face from above, enabling the lateral curves to be seen. One cutting edge forms an inner curve; another edge forms an outer curve that appears larger and closer to the floor. The proper cutting edge is always the curve that appears lower and further from the terminal shank. Unlike universal instruments that require parallelism of the handle with the tooth, area-specific instruments require parallelism of the terminal shank with the tooth. When in this position against a tooth surface, if the correct edge has been chosen, only the back should be visible. If the face is visible (reflecting light), flip the instrument to use the contralateral working end.

Langer curettes have a combination of universal curette qualities (face 90 degrees to shank) with the Gracey curvature of shanks. Langers and Graceys are available with blades that are shorter in length (mini) that make them particularly suitable for use on small dogs and cats.

PRINCIPLES OF SCALING

Adaptation of hand-scaling instruments is the application of the cutting edge against the tooth. Approximately one third of the cutting edge of the tip should remain in contact with the tooth, and constant attention to this detail will prevent damage of the soft tissues as a result of trauma from the tip or toe (Figure 32-44). As the curvature of the tooth changes, adjustments must be made to that portion of the cutting edge that is adaptable to the tooth. Use of the thumb against the handle will enable the instrument to be rolled to maintain the contact of the cutting edge around curves.

Angulation refers to the relationship of the face of the instrument to the tooth. When inserting a curette into a pocket, the angulation of the face should be as close to zero as possible (Figure 32-45). In this position, the face would be parallel with the root surface and the back of the blade would be against the soft tissue lining of the pocket. When the blade is positioned at the bottom of the pocket or apical to the intended piece of calculus, the angle should be opened, by tilting the handle, to the scaling and root planing angle of 45 degrees to 90 degrees, more often between 60 degrees to 80 degrees. Using an angle that is too closed will create a burnishing (smoothing) of the calculus, rather than biting into it for removal. An angle that is too open will place the noncutting edge sharply against the lining of the pocket when using a curette. This technique is useful if the operator purposely desires to perform a gingival curettage.

Strokes used when performing dental procedures will vary according to the task. When hand scaling, the initial stroke is for assessment to determine the topography of the tooth surface by lightly feeling for irregularities. This exploratory stroke is also performed with an explorer or with the tip of a power scaler when the power is not activated. When using scalers and curettes, once an irregularity is detected, the working stroke is performed by applying lateral pressure against the tooth and pulling the blade either vertically, horizontally, or obliquely in a short, controlled stroke. A root-planing stroke is longer in length, and light lateral pressure is used. Apply the minimum number of strokes necessary to accomplish the task.

SHARPENING

Thorough periodontal débridement can only be accomplished with the use of sharp instruments. Each stroke of a sharp instrument against the tooth will wear away the metal of the cutting edge, causing it to transform from a precise sharp line at the junction of the face and lateral surfaces into a dull, rounded surface. Using a dull surface requires heavier lateral pressure against the tooth, reducing tactile sensitivity and creating hand fatigue. The dull surface will burnish the calculus, rather than causing it to be shaved off. Once burnished, this calculus is difficult to detect and remove.

Instrument sharpening can be accomplished manually using sharpening stones or with the help of mechanical sharpening devices. Either way, it is critical to have a thorough understanding of the instrument design, including the cross-sectional shape and the line angles between surfaces, to enable a sharp cutting edge to be reestablished without creating changes in the instrument’s original design.

Sharpening stones typically used for dental instruments include Arkansas, India, ceramic, and a synthetic composition, each differing in coarseness. A few drops of lubricant are required on most stones to keep metal particles from embedding into the stone and to reduce heat friction. Lubricate with sharpening oil on Arkansas and India stones; the ceramic stone can be lubricated with water or used dry, and the composition stone requires water.

Several methods of manual sharpening can be used; however, the technique that requires the instrument to be held stationary while the stone is moved provides a good view of the blade so that the angle can be precisely controlled. Hold the instrument in a palm grasp with the blade facing you and the face parallel to the floor. Elbows should be braced against the side of the body for stability, and the procedure should be performed under good lighting that is reflecting off the face. Hold the stone perpendicular to the face (Figure 32-46), beginning at a right angle (90 degrees), then tilt the stone against the lateral surface so the angle opens to 100 degrees to 110 degrees. An angle guide can be purchased or made by using a protractor to aid in visualizing correct angles.

Using light pressure, move the stone in short up-and-down strokes against the lateral surface of the instrument, beginning at the heel of the instrument and working toward the toe, continuing around the toe when sharpening curettes (Figure 32-47). At the point where sharpening allows the lateral surface to meet sharply with the face, a black “sludge” will appear on the face. Finish with a few more light strokes, ending with a down stroke of the stone to remove wire particles that have been lifted from the metal.

Sharpening methods that include sharpening of the face should be avoided because the blade will be weakened and may break during débridement. Instruments that have been oversharpened and are excessively thin should be discarded.

CLOSED EXTRACTIONS

While the regional block is taking effect, a preextraction radiograph should be taken of the tooth to assess for evidence of root pathologic conditions that may affect the surgical approach. A closed technique is best reserved for single-rooted teeth or teeth that have severe periodontal disease. Once the regional nerve block is placed, the gingival attachments around the tooth are separated with either a periosteal elevator (Figure 32-60), dental luxator, or scalpel blade. After the soft tissue attachments have been severed, a dental elevator of appropriate size and shape (Figure 32-61, A, B) is placed in the periodontal space on the mesial or distal surface of the crown. Once placed in the space, gentle pressure is placed to seat the elevator within the tooth and alveolar bone, and the handle of the elevator is rotated slightly to stretch the periodontal ligament fibers. If elevation is done correctly, the tooth will be observed to move slightly when the elevator is rotated. Pressure is held for 10 seconds, and then the elevator is advanced apically and rotated against the root in the opposite direction to create pressure and hold again. The goal is to fatigue the periodontal ligament and prevent tooth root fracture. Larger elevators are used as the periodontal ligament breaks down and allows more room to place a larger instrument. The temptation to wiggle the elevator in an attempt to obtain a deeper position in the periodontal space should be avoided because this will often cause breakdown of the alveolar bone and loss of leverage. The elevator may also be placed on the palatal or lingual surface and the vestibular surface within the periodontal space to stretch the periodontal ligament fibers around the entire circumference of the tooth. Elevators come in a variety of shapes and sizes, and it is important to have access to different sizes for different situations. When grasping a dental elevator, the handle should rest securely in the palm of the hand. The index finger should be extended so that if the elevator slips, the index finger will help to stop the advancing of the elevator into deeper structures (Figure 32-62). Ocular and brain trauma have been documented in cases where dental elevators have slipped during extraction procedures. To prevent this, forces used must be well controlled and should be generated in the lateral or medial direction rather than in the apical direction. The gingival tissue is apposed to close the extraction site with 4-0 or 5-0 monofilament absorbable suture in a simple interrupted pattern. Sterile extraction packs containing necessary instruments may be wrapped and prepared for use (Box 32-9).

SURGICAL EXTRACTIONS

As a result of the large surface area and multirooted nature of carnivore teeth, surgical extraction is often a less traumatic option than attempts of removing a firmly rooted tooth by closed extraction. As with closed extractions, the gingival attachments are separated from the tooth crown with a periosteal elevator, dental luxator, or scalpel blade. A flap is created, depending on the location and underlying root structure. A flap with no releasing incisions is called an envelope flap. A flap with one releasing incision is a triangle flap, and a flap with two releasing incisions is called a pedicle flap. Each situation should be assessed individually to decide which type of flap is necessary to provide the optimal access and tension-free tissue closure while inflicting the minimum amount of soft tissue trauma. Pedicle flaps are created with a broad base to ensure good blood supply and adequate tissue for closure. Once the flap is raised, a round carbide bur is used in a water-cooled, high-speed handpiece to create a window in the buccal bone of roots to be extracted. Multirooted teeth are separated with a tapered fissure bur. Once the window is created and roots are sectioned, minimal force is necessary to gently pry the roots and attached crown segments from their sockets. Once the roots are removed in their entirety, rough bone edges are smoothed with a large round diamond bur. The alveolus of each root is curetted and lavaged with sterile isotonic solution or 0.12% chlorhexidine. The periosteum is separated from the mucosa to provide adequate tension-free tissue to close the defect. The flap is closed with 4-0 or 5-0 absorbable monofilament suture in a simple interrupted pattern. Occasionally, osteoconductive or osteoinductive products may be placed in the alveolus before closure if it is suspected that the product will not act as a nidus and will help to prevent significant bone loss in the area of the extraction. A postextraction radiograph should be taken to document complete removal of the roots in cases where the roots were not retrieved easily.

When a root fractures, additional instruments will be needed to retrieve the retained tooth root. Root tip elevators and root tip forceps are valuable tools in root tip retrieval (Figure 32-63). Care should be taken to prevent dislodging the root tip into the nasal passage or mandibular canal. Cotton-tip applicators are helpful to control hemorrhage in the alveolar socket to visualize the root tip. Avoid blowing air from an air or water syringe into the socket. Although this may help visualize the root, a fatal air embolism may occur. The pet should be given no hard food or treats for 14 days postoperatively. Postoperative antibiotics are generally not necessary following extraction procedures. The AVDC has developed a position statement regarding the use of antibiotics in dental patients (Box 32-10).

TOOTH RESORPTION

Tooth resorption is common in cats and rare in dogs. Prevalence studies have found that 20% to 70% of cats are affected by this problem, depending on the population of cats and the investigative methods employed. The lesions are usually appreciated clinically at the cervical portion of the tooth (the junction of where the crown meets the root, sometimes referred to as the “neck” of the tooth), which is often hidden by the gingiva. However, recent histologic studies have found that these lesions begin on the root surface, and radiographic changes can often be seen before a clinical lesion is obvious. When a lesion develops at the gingival margin, the adjacent gingiva often covers these lesions with a combination of hyperplastic gingiva and granulation tissue (Figure 32-64, A).

A fine explorer should be used to check for irregularities, as described earlier in this chapter. In the past, restorations have been placed in lesions, but follow-up studies have shown poor long-term results with restoration. Therefore extraction is the treatment of choice. Dental radiographs of these teeth are necessary to evaluate the severity of resorption and to guide treatment.

Sometimes it is not possible to perform a complete tooth extraction because of severe root resorption where a portion of the root has been replaced by a reparative bone-cementum material. When this occurs, the tooth root becomes incorporated into the adjacent alveolar bone. Radiographic evidence of this is seen by loss of periodontal ligament space and decreased root density, approximating that of the surrounding bone density (Figure 32-64, B). When this radiographic appearance is seen, in the absence of periodontal or endodontic disease, it is possible to perform a crown amputation where hard tissue with characteristics of tooth root is removed and resorbed root that has been replaced by bone is not removed. The tooth crown and coronal root segment are removed with a dental bur and high-speed handpiece. The crestal alveolar bone is smoothed with a dental bur, and the gingiva is closed with absorbable suture over the crown amputation site.

ORTHODONTIC PROBLEMS

DENTAL TRAUMA

Dogs and cats can generate large amounts of biting, pulling, and grinding forces, and their teeth are often the recipients of dental trauma. This trauma can be exhibited as wear (attrition or abrasion), uncomplicated tooth fracture (no pulp exposure), or complicated fracture (pulp exposure).

Many dogs will cause severe abrasion of their teeth by chewing on inappropriate objects, such as rocks or fences. The teeth most commonly fractured are the canines and maxillary fourth premolar teeth (see Figure 32-22, A). Attrition and abrasion usually occur on the incisors and canines, but can be seen on the premolars and molars. If the dental wear occurs slowly, odontoblasts will deposit tertiary (reparative) dentin within exposed dentinal tubules to prevent pulp exposure as enamel and dentin are lost. Tertiary dentin may be seen on the surface of worn teeth as a brown or black dot (see Figure 32-22, B). A dental explorer should be run over the tooth surface to make sure the pulp tissue is not exposed. When the pulp tissue is exposed, the tip of the dental explorer will fall into the pulp chamber as it crosses the surface of the tooth, whereas tertiary dentin feels smooth as glass with the explorer.

In acute fractures with pulp exposure, the tooth may bleed from the exposed pulp surface. If the tooth is treated within the first 48 hours, vital pulp therapy may be successful. This procedure involves removing the coronal pulp tissue (the pulp tissue in the tooth root remains), covering the pulp tissue with a medicament, and sealing the coronal exposure site with appropriate dental restorative materials.

All teeth with exposed pulp tissue should be treated either by endodontic treatment (conventional root canal, vital pulp therapy) or by extraction. If left untreated, infection from the exposure site will spread to the periapical tissues, and a periapical abscess will develop with time. The client may notice ipsilateral facial swelling or a draining tract just below the medial canthus of their pet’s eye (Figure 32-72, A, B). The majority of periapical abscesses will not form a fistula through the skin, which means that unless the teeth of these pets are examined for endodontic disease, many abscesses go untreated. These abscesses can be painful and are a source of infection, which can spread to other areas of the body.

Discoloration is another sign of endodontic disease, commonly seen as a result of prior trauma to the pulp resulting in pulpitis (Figure 32-73). Ninety-two percent of discolored teeth show evidence of partial or complete pulp necrosis on exploratory pulpotomy. Because dogs and cats do not articulate their discomfort, evidence of pulpitis warrants endodontic or exodontic therapy to relieve possible pain in a tooth affected by pulpitis.

ORAL NEOPLASIA

Oral tumors account for only 6% of all neoplasia in dogs and 3% to 12% in cats, these tumors are often aggressive, and prognosis depends on early detection. The most common oral tumor in cats is squamous cell carcinoma (SCC), which accounts for approximately 70% of all oral tumors in cats (Figure 32-74). To be able to provide a cure for SCC, early detection is particularly important in smaller patients (cats and small dogs) because of the need to obtain clean surgical margins while still maintaining adequate function.

In dogs, tumors may be benign or malignant. The most common benign tumor in dogs is a gingival tumor that in the past has been referred to as an epulis (plural: epulides). The epulides were categorized as fibromatous, ossifying, and acanthomatous; the latter is the most locally invasive. A change in the terminology of these tumors has been made to more accurately reflect their histologic appearance. Fibromatous and ossifying epulides are now categorized together as “peripheral odontogenic fibromas.” Acanthomatous epulis is now referred to as canine acanthomatous ameloblastoma. Peripheral odontogenic fibromas do not typically invade bone and usually do not recur if the tooth of origin and its periodontal ligament are removed (Figure 32-75, A). Canine acanthomatous ameloblastoma requires removal of the tumor with a minimum of 1 cm of normal tissue in all directions to prevent recurrence (Figure 32-75, B). Most oral tumors are not responsive to chemotherapy or radiation, but canine acanthomatous ameloblastoma does respond to radiation. Surgery (mandibulectomy or maxillectomy) is often the treatment of choice, however, because development of malignant tumors at the site of radiation has been reported with this tumor type.

The most common malignant tumors in dogs are malignant melanoma, SCC, fibrosarcoma, and osteosarcoma. These tumors are locally invasive and have the potential to metastasize to regional lymph nodes or to the lungs. After staging the patient to determine the extent of disease, surgery or radiation is usually recommended to deal with the primary tumor, and metastases are dealt with by either chemotherapy, radiation of metastatic nodes, or immunotherapy. Malignant melanoma may be pigmented or amelanotic. A vaccine has recently been developed for treatment of dogs with malignant melanoma, which has shown promise in increasing survival times.

Dogs and cats that undergo radical maxillectomy and mandibulectomy for removal of an oral tumor generally function well postoperatively, and the majority of clients are pleased with long-term quality of life and appearance. Cats recover more slowly from maxillectomy and mandibulectomy and often require placement of a feeding tube (usually an esophagostomy tube) during the recovery period, whereas dogs usually eat and drink within 24 hours after surgery.

STOMATITIS

Diffuse inflammation of the entire oral cavity is seen commonly in cats and occasionally in dogs. When inflammation is confined to the gingiva, it is referred to as gingivitis. When the inflammation extends beyond the mucogingival junction, it is called stomatitis (Figure 32-76). Stomatitis may be due to a variety of causes, including ingestion of a caustic substance, uremia, viral exposure, plant foreign bodies, allergic response to drugs, or most commonly immune-mediated causes. Cats are often affected by a type of stomatitis referred to as lymphocytic-plasmacytic stomatitis, which can involve gingiva, alveolar mucosa, buccal mucosa, sublingual mucosa, and even the mucosa of the caudal oral cavity lateral to the palatoglossal folds. Cats often have decreased appetite or anorexia, halitosis, dehydration, and blood-tinged saliva.

The cause of LPS is not clear, but it appears that cats develop inappropriate inflammation in the presence of even small amounts of plaque accumulation. Many cats with LPS concurrently shed both herpesvirus and calicivirus. These viruses may have an effect on the immune system, resulting in an overzealous or deficient immune response to plaque. Therefore plaque control in the form of frequent dental cleanings and home care is important. Unfortunately, many LPS cats are so painful that home care is not feasible. Immunosuppressive agents, such as corticosteroids and cyclosporine, help in many cases, but when medical therapy fails or causes unacceptable side effects, full-mouth extractions or nearly full-mouth extractions have been shown to provide resolution of oral discomfort in approximately 80% of cases. When seen in dogs, stomatitis may be due to autoimmune diseases, such as pemphigus vulgaris or bullous pemphigoid.

MASTICATORY MUSCLE MYOSITIS

Masticatory muscle myositis is an immune-mediated disease where the immune system forms antibodies toward a specific component of myosin found only in muscles of mastication. Patients affected by this disease may be seen either in the acute phase of the disease, which is painful, or in the chronic phase of the disease, where much scarring has already taken place. Patients in the acute phase will often have the complaint of pain upon opening the mouth, decreased appetite, or dropping of food. These patients often have swelling of the temporal, masseter, and/or pterygoid muscles, which may occasionally also cause exophthalmus. Patients in the chronic phase often have severe temporal and masseter muscle atrophy and inability to open their mouth as a result of severe scar tissue formation. The goal is to diagnose the disease before these chronic changes occur because it is difficult to deal with in the chronic phase. Diagnosis is made by sending serum and muscle biopsies to the comparative neuromuscular laboratory at the University of California, San Diego. Treatment of the acute phase involves a long, slow taper of oral corticosteroids, beginning at an immunosuppressive dose of 1 mg/kg twice daily. Some patients need to be on some level of steroids for life to prevent recurrence.

JAW FRACTURES

Jaw fractures are common in dogs and cats with motor vehicle trauma, high-rise syndrome, or severe periodontal disease resulting in a pathologic fracture. Most jaw fractures benefit from some type of rigid fixation. One of the most common types of jaw trauma is a symphyseal separation, where the right and left mandibles separate at their rostral fibrous union called the symphysis. A cerclage wire placed behind the canine teeth for no more than 4 weeks allows for stability while the symphysis heals (Figure 32-77, A, B).

More involved jaw fractures may be repaired by use of interdental wire and acrylic composite, transosseous wiring, miniplates, external fixation, or maxillomandibular fixation. Sometimes teeth along the fracture line may be able to be used as anchor points, but teeth affected by severe periodontal disease should be removed because the fracture will likely not heal when the diseased tooth acts as a nidus for infection.

Patients presenting acutely with a mandibular fracture may benefit from placement of a tape muzzle (Figure 32-78) to stabilize the fracture until surgical treatment is performed. The tape muzzle is created using one piece of tape (adhesive side outward) around the muzzle itself, which is attached to a second piece that wraps around the head below the ears. The muzzle should be tight enough to minimize motion, but loose enough to prevent irritation of the soft tissue and to allow the tongue to move between the incisor teeth to allow for drinking and eating food of a slurry consistency. Tape muzzles are sometimes considered the definitive treatment of choice in young patients where rigid fixation may adversely affect growth of the healing mandible.

DENTAL ANATOMY AND PHYSIOLOGY

Horses have 24 deciduous teeth and 36 to 44 permanent teeth, depending on the presence or absence of canine and first premolar teeth. At eruption, the occlusal surfaces of equine teeth are fully covered by cementum, compared with dogs and cats that have cementum covering only the root. Beneath the crown cementum, a thin layer of crown enamel is present. Both of these layers get worn away, exposing an intricate, wavy combination of cementum, dentin, and enamel on the occlusal surface. Equine mandibular incisor teeth develop features of their occlusal surface that have been traditionally used to estimate age. Because much variation is seen in the rate of tooth wear based on breed, nature and quality of food, and environment, aging horses by this technique should be considered an approximate estimate. Eruption times are the most accurate method of determining age, but this can only be used in horses that have not erupted their complete permanent dentition. Of all the changes on the occlusal surface of the incisors, the appearance of the dental star is one of the more reliable features. The dental star is composed of dentin, and the position of the star moves from the lingual edge of the occlusal surface to the center as the horse ages. Galvayne’s groove, a groove that appears on the labial surface of the third incisor in some horses over the age of 10, was once considered to be an excellent method of aging horses between 10 to 30 years of age. It has since been determined that its presence is inconsistent and is of little value in determining the age of a horse.

The canine teeth are usually absent or rudimentary in female horses, but males typically have four permanent canine teeth that erupt at 4 to 6 years of age in the diastema between the incisors and the cheek teeth. The permanent first premolars are referred to as “wolf teeth,” and are much smaller and located rostral to the other premolars. The first premolar has no deciduous precursor. Wolf teeth are present in 24.4% of females and 14.9% of male horses. Wolf teeth occur more commonly on the maxilla. These teeth are often extracted because of concerns for causing oral discomfort, especially when the bit contacts this tooth. The premolars and molars are collectively referred to as the “cheek teeth.” Not including the wolf teeth, each quadrant should contain six cheek teeth (second, third, and fourth premolars and first, second, and third molars). A numbering system has been developed for equine teeth based on the Triadan system (Figure 32-79, A, B). The cheek teeth are closely arranged with no spaces in between them, so the six teeth in one quadrant function as a single unit. The occlusal surfaces of the cheek teeth have many grooves and ridges composed of enamel, cementum, and dentin, which provide varied surfaces for grinding of food material. The upper jaw is wider than the lower jaw, a term referred to as anisognathism. The occlusal surface is normally angled at 10 degrees to 15 degrees in a downward slope toward the buccal aspect of the teeth. In horses with painful dental disease or when fed an inappropriate diet (too little forage), this angle may be increased, resulting in a more vertical angulation of the occlusal surface. This condition is termed “shear mouth.”

In horses, the left and right mandibles are not separated by a symphysis as in dogs and cats. The mandibles fuse at the midline at approximately 3 months of age in the horse. In contrast to carnivores, the TMJ is designed for horizontal movement, and the muscles necessary to provide this movement are more developed. Dogs and cats have large temporal muscles on the top of their head that allow for strength in vertical movement of the mandible, whereas horses have well-developed masseter and pterygoid muscles to allow for horizontal grinding movement. Horses have well-developed muscles of the lips that allow them to prehend food, and the commissure of the lips is positioned rostrally, making examination of the caudal cheek teeth challenging.

DENTAL EXAMINATION AND IMAGING

Common presenting problems of horses with severe dental disease include weight loss, dropping of food (quidding), head shaking, and tilting of the head during mastication. Routine oral examinations are helpful to detect dental abnormalities in their early stages. Dental disease interferes with normal mastication, resulting in larger feed particle size at the time of deglutition. This may predispose horses and donkeys to impaction colic or esophageal choke. Dental disease may also contribute to systemic infection as a result of hematogenous spread of periodontal pathogens.

Extraoral examination should include observation for evidence of facial swelling, atrophy of masticatory muscles, and presence of ocular, nasal, or oral discharge. The patient’s stable floor should be evaluated for evidence of quidding, such as dropped grain and partially chewed boluses. Feces should be evaluated for particle size because large stems of hay and whole grain indicate incomplete mastication. Young horses between 2.5 and 4 years old will have symmetrical, nonpainful bony enlargement of the mandible and/or maxilla associated with eruption of the permanent cheek teeth. Sharp points of the buccal surface of the maxillary teeth may be palpable extraorally. Palpation may cause the horse to resist if points are present. They should be removed before placement of a full-mouth speculum because the cheeks will be pushed tightly against the points once the mouth is opened. Observe the lips for evidence of ulcers, tumors, or bit injuries, especially in the area of the commissure.

Thorough examination of the oral cavity of the horse requires sedation. A self-supporting mouth speculum, a strong light source, a dental mirror, and long-handled dental picks are helpful to assess hard and soft tissue structures and remove food material from areas of interest. Intraoral cameras are available to provide visualization and magnification of difficult areas. Skull radiographs are helpful to diagnose subgingival abnormalities (Figure 32-80). Various views may be necessary, including lateral, lateral oblique, dorsoventral, open- and closed-mouth views. Use of a radiopaque object (such as a needle or gutta percha point) placed in the center of a facial swelling or draining tract before taking a radiograph may help to determine the tooth of origin.

As a result of the large patient size, small film size, and limited intraoral access, intraoral dental radiography is limited to use in imaging of the incisor teeth. If skull radiographs do not show obvious pathologic conditions in a case where dental disease is suspected, other imaging techniques, including nuclear scintigraphy, computed tomography (CT), and magnetic resonance imaging (MRI), may be an option.

COMMON DENTAL PROBLEMS OF HORSES

Endodontic abnormalities occur as a result of disease of the inner chamber of the tooth, which is most commonly seen in the form of a tooth root abscess. Tooth root abscesses occur as a result of exposure of the pulp to the oral environment or death of a tooth with hematogenous spread of bacteria to the compromised site. Pulp exposure may occur as a result of tooth fracture, excessive wear, or decay. Tooth root abscesses may cause a large swelling of the surrounding bone and soft tissue.

The caudal maxillary tooth roots (fourth premolar, first, second, and third molar) are located just ventral to the maxillary sinus, so infection of any of these teeth may result in sinusitis and chronic unilateral nasal discharge. Infection as a result of tooth root abscesses will not permanently resolve with administration of antibiotics, although antibiotics may provide temporary improvement. Extraction or endodontic therapy is necessary for long-term success. Extraction is often difficult because of limited access and the large amount of subgingival tooth structure. Cheek teeth often are approached from an extraoral technique. Although incisors, wolf teeth, and canines can usually be extracted via an intraoral technique, cheek teeth usually need to be approached by buccotomy or repulsion.

Orthodontic abnormalities refer to those abnormalities of occlusion (the normal spatial relationship of teeth and jaws), either as a result of abnormal development, eruption, or wear. Maxillary brachygnathism (or mandibular prognathism) is a developmental disorder where the lower jaw is relatively shorter than the upper jaw. A common term for this condition is “parrot mouth.” One goal of treatment is to prevent or minimize the degree of abnormal tooth wear that can occur from malocclusion. Orthodontic procedures can be performed to prevent or correct ventral deviation of the incisive bone and upper incisors and to attempt to overcome the jaw length discrepancy early in life while growth is still occurring. The opposite of parrot mouth is referred to as “monkey mouth,” which occurs when the maxilla is relatively shorter than the mandible (resulting from maxillary brachygnathism or mandibular prognathism). This condition is seen most commonly in miniature horses.

Horses with jaw length discrepancies require more frequent occlusal adjustments, but any horse should be evaluated at least yearly for abnormal wear patterns. Floating is the term used to describe the process of mechanically adjusting the occlusal surfaces of the teeth. Flat files (floats), which come in hand and electrically driven versions, are used to remove raised areas, such as hooks, ramps, or points (Figure 32-81). Removal or loss of a tooth can result in drift of adjacent teeth into the vacancy, resulting in abnormal occlusion patterns. Similarly the tooth from the opposing arcade may overgrow into this void as a result of lack of normal wear. Patients with these problems will require more frequent examinations and occlusal equilibrations as necessary (Box 32-11).

Another orthodontic problem seen in foals is wry nose. Wry nose is a deviation of the incisive bone, maxilla, and nasal septum laterally from the midline. Affected foals may have difficulty suckling or prehending forage, and dyspnea resulting from deviation of the nasal septum can be so severe that a tracheostomy may be necessary. It is believed to be a hereditary condition most commonly seen in Arabians and miniature horses. Orthognathic surgical correction often requires two separate surgeries and is usually attempted between 5 and 7 months of age.

Periodontal abnormalities refer to loss of or damage to the attachment structures of the teeth, which consist of the periodontal ligament, cementum, alveolar bone, and gingival connective tissue. Gingivitis is one of the earliest signs of periodontal disease, where the gingiva may appear hyperemic, edematous, and bleeding more readily than normal. Gingival recession may be seen, or alternatively, loss of periodontal ligament attachment may result in development of a periodontal pocket. Although the cause of periodontal disease in horses is similar to that described for dogs and cats earlier in this chapter, treatment is challenging because of limited accessibility of the cheek teeth of horses. The tooth-cleansing process associated with mastication of abrasive substances is an important part of keeping teeth periodontally sound. Therefore any dental pathologic condition, such as abnormal wear and oral ulceration, should be corrected to prevent preferential use of certain teeth and disuse of others. Depending on their accessibility, deep periodontal pockets may be débrided and lavaged. Off-label use of a canine doxycycline gel (Doxirobe) has been described to deal with periodontally affected teeth that have not lost enough attachment to require extraction. Teeth with severe attachment loss and mobility require extraction.

Cemental hypoplasia is a developmental abnormality that can occur in all equine teeth and may predispose maxillary cheek teeth to endodontic disease, tooth fracture, abnormal occlusal patterns, and caries. Caries is the medical term that describes “cavities” caused by tooth decay associated with acids created by bacterial fermentation. When a carious lesion occurs within the infundibulum (the infoldings of the occlusal surface of incisors and cheek teeth) of a tooth, it is referred to as infundibular decay. Restoration of these lesions with composite filling material has been advocated by some equine dentists.

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