to be imaged. Others can image all body areas and more than hard tissue.
Intraoral films (no. 2 and no. 4 common sizes)Require development: chairside or automatic developer.Time lapse before images can be viewed on view box.Retakes due to inexperience or exposure adds to anesthetic time.
Digital intraoral radiography (Figure 3.2)Direct digital radiography with solid‐state sensor:Sensor typically size no. 2, similar to no. 2 periapical intraoral film.Allows immediate review of image for adjustments.Sopix sensor has widest latitude of exposure, minimizing retakes [4].Sensor may be expensive to replace.Indirect digital radiography:Phosphor plates allow for additional sizes such as no. 4 for larger view.Takes additional time to scan the phosphor plate in order to view the image and retake to adjust for positioning or exposure.
Cone beam computed tomography (three‐dimensional imaging) (Figure 3.3)Complete a full mouth (skull) scan in as little as 24 seconds, minimizing anesthesia [3].Visualize three‐dimensional structures without obstruction such as maxillary architecture.Confirm periapical changes, tooth resorption, and temporomandibular joint (TMJ) architecture earlier, with 50% more sensitivity [5,6].Image pulmonary nodules as small as 1 mm, which is up to nine times smaller than nodule detection using three‐dimensional thoracic radiography [7].Find twice as many traumatic injuries as missed with conventional radiology [8].
Figure 3.2 (Left) No. 4 (occlusal) and no. 2 (periapical) phosphor plates for use in indirect digital radiology. The sizes are similar to commonly used nondigital intraoral films. (Right) Sopix digital sensor, similar to no. 2 size of intraoral dental film.
Figure 3.3 Example images acquired in a CBCT scan: (a) sagittal, (b) axial, and (c) coronal “slices”; (d, e) three‐dimensional reconstructions for viewing. Maxillary obscured periapical and periodontal disease in the 200 quadrant is revealed.
PROCEDURE
Taking Radiographs
For intraoral films, the patients must be under general anesthesia: all considerations should be met (preoperative diagnostics, patient monitoring and support).
Some tools that can help in taking images include the following (Figure 3.4):Flexible spiral perm roller (from beauty supply stores): can be used to keep sensor in proper position and as a soft mouth gag or wedge. Spring‐loaded mouth gags are inappropriate for veterinary dentistry, are known to cause blindness in cats, [9] and are also risky for dogs.Two tongue depressors joined with a push pin: simple device to help position radiographic beam for intraoral films.Roll of tape: to visually estimate the direction from which the radiographic beam should be aimed.
Positioning of the film within the oral cavity and positioning of the radiographic beam can be a challenge.Place flat aspect of sensor or white side of film towards X‐ray source.Place film so image of roots will be captured, not crown (Figure 3.5). With a larger dog, this may involve placing the sensor or film further onto the palate or deeper in the intermandibular space. If the periodontal bone margin needs to be evaluated, place sensor centered at the neck of the tooth.
Parallel Technique (Sandwich Technique)
Intraoral film or sensor placed lingual and parallel to (just inside and flat against) the mandibular premolars and molars: place the diagonal of the film across the position of the roots, with a corner sticking into the intermandibular space (Figure 3.6).
Radiographic beam aimed perpendicular to both film and teeth.
Shadow Technique (Modified “Bisecting Angle” Technique)
In all other teeth, the sensor/film cannot be placed parallel to the teeth; there will be some space between the tooth/root and film.
Position film as close to the tooth/root to be imaged as possible: you need to evaluate the roots, not the crown.Figure 3.4 Three tools to help with taking radiographs: spiral perm roller for keeping sensor/film in place; two tongue depressors attached with a push‐pin; and roll of tape.Figure 3.5 Intraoral films should be placed such that the image of the roots, not the crown, will be seen on the film; this film was placed against the palate to image the roots of the upper fourth premolar.Figure 3.6 Parallel placement of an intraoral film to image the mandibular premolars and molars, as demonstrated on this cat skull. Note the corner is pushed into the intermandibular space.
If the beam was aimed perpendicular to the film (Figure 3.7):This would result in a “shadow” or image of the tooth on the film that would be too short (think of a tree at noon).Therefore, perpendicular to film: too short (of an image).
If the beam was aimed perpendicular to tooth root(s) (Figure 3.8):This would result in a “shadow” or image of the tooth on the film that would be too long (think of a tree at daybreak).Therefore, perpendicular to tooth: too long (of an image).
Split the difference: come halfway between the two positions (Figure 3.9):The resulting “shadow” or image will be a compromise between the foreshortened and elongated images, with the image the approximate length of the tooth itself.In some of the images, a positioning device was made of two tongue depressors. The blue portion is aimed perpendicular to the film, and the red portion is aimed perpendicular to the tooth root. The X‐ray beam/source is then positioned midway between the two.Figure 3.7 When imaging these maxillary incisors and canines, if the beam were aimed perpendicular to the film, the images would be foreshortened.Figure 3.8 If the beam were aimed perpendicular to the teeth (roots), the images would be elongated.The positioning tool made of regular tongue depressors (see Figure 3.4) has the terms “Perpendicular to film – too short” and “Perpendicular to tooth – too long” printed on them to help determine the proper angles.
Other teeth:Mandibular incisors/caninesPerpendicular to film (Figure 3.10): too short.Perpendicular to teeth (Figure 3.11): too long.Split the difference (Figure