INDICATIONS

Intraoral radiology is an integral part of veterinary dentistry, from diagnostics to therapy to evaluation of response to therapy.
- Ideal: full mouth radiographs on every patient, each dental visit
- Survey: assess normal anatomy, use as baseline
- Tooth abnormalities: size, structure, variation in number (absence or multiple)
- Periodontal disease: assess extent and nature of periodontal bone loss
- Endodontic disease: assess pulpal vitality—canal width and presence of periapical bone loss
- Acquired diseases: caries, tooth resorption
- Trauma: evaluate extent of osseous and dental damage
- Neoplasia: evaluate extent of osseous involvement

EQUIPMENT

Radiographic unit
- A dental radiographic unit at the dental station provides convenience to take radiographs of every patient (Fig. 4-1)
  - Wall-mounted, on a movable stand, or handheld units
- Digital radiography
  - Direct digital radiography with sensor
    - Sensor typically size #2, similar to #2 periapical intraoral film
    - Allows immediate review of image for adjustments
    - Sensor is expensive to replace
  - Indirect digital radiography
    - Phosphor plates allow for additional sizes
    - Takes a short time to scan the phosphor plate in order to review the image
- Intraoral films—#2 and #4 are the common sizes (Fig. 4-2)
  - Require development—chairside or automatic developer
  - Time lapse before images can be reviewed on viewbox

Figure 4-1 A dental radiographic unit is convenient for use at the dental station.

Figure 4-2 Commonly used intraoral films: sizes #4 (occlusal), #2 (periapical), and #2 (digital sensor).

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 (Fig. 4-3)
- Flexible spiral perm roller (blue—found at beauty supply store): can be used to keep sensor in proper position and as a soft mouth gag or wedge
- Two tongue depressors joined with a pushpin: simple device to help position radiographic beam for intraoral films
- Roll of tape: to 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 toward X-ray source
  - Lead sheet on the back side of the film prevents backscatter, and embossed dot on film will facilitate identification of teeth on image (Fig. 4-4)
- Place film so image of roots will be captured, not crown (Fig. 4-5). 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 needed to be evaluated, place sensor centered at the neck of the tooth.
Parallel 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 (Fig. 4-6)
- 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
- If the beam was aimed perpendicular to the film (Fig. 4-7)
  - 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) (Fig. 4-8)
  - 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 in between the two positions (Fig. 4-9)
  - 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 green 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.
  - The positioning tool made of regular tongue depressors (Fig. 4-3) has the terms “Perpendicular to the Film—Too Short” and “Perpendicular to the Tooth—Too Long” printed on them to help determine the proper angles.
- Other teeth: dogs
  - Mandibular incisors/canines
    - Perpendicular to film (Fig. 4-10)—too short
    - Perpendicular to teeth (Fig. 4-11)—too long
    - Split the difference (Fig. 4-12)
  - Maxillary upper fourth premolar
    - Perpendicular to film (Fig. 4-13)—too short
    - Perpendicular to teeth (Fig. 4-14)—too long
    - Split the difference (Fig. 4-15)
- Other teeth: cats
  - Maxillary incisors/canines
    - Perpendicular to film (green tongue depressor) (Fig. 4-16)
    - Perpendicular to teeth (red tongue depressor) (Fig. 4-17)
    - Split the difference (Fig. 4-18)
  - Mandibular incisors/canines
    - Split the difference (Fig. 4-19)
  - Maxillary fourth premolar (see “Hint” section)
- When positioning the beam, make sure it is aimed directly over the tooth (maxillary fourth premolar) or at midline (mandibular or maxillary incisors and canines for symmetry) (Fig. 4-20)
  - Adjust beam (laterally or obliquely for canines or mesially or distally for premolars) to “move” the superimposed apices away from each other (Fig. 4-21)
- Hint
  - Maxillary incisors and canines: on most dogs and cats (not brachycephalic breeds), align the flat end of the positioning device (blue) to be parallel to the ventral fold of the nares (or haired portion of muzzle just under the nares) (Fig. 4-22); in many cases, this will closely approximate the correct beam alignment. Position the beam initially based on the nares, and confirm the angle.
- Challenging radiographs
  - Dog: maxillary canine apex
    - Place sensor/film centered at the second premolar and palpate apex of canine tooth (Fig. 4-23)
    - Aim beam toward palpated apex, slight oblique off midline (Fig. 4-24)
  - Dog: maxillary molars
    - Place sensor/film lengthwise palatally—lined up with the two molars
    - Aim beam from above and slightly behind—almost directed aimed at film (Fig. 4-25)
  - Dog: mandibular first premolars—challenging to place sensor far enough rostral in the intermandibular space for true parallel image
    - Intraoral: with sensor/film in place, aim beam from a position below (ventral) and rostral; this will “push” the image onto the film (Fig. 4-26)
    - Extraoral: with sensor/film underneath the premolar area on the opposite side, aim beam at an oblique to where the mandibular teeth on the other side are not superimposed (use tape roll to assist positioning) (Fig. 4-27)
  - Dog: mandibular second and third molars
    - Position sensor/film further caudally, but also dorsally—do not let it slide ventrally (keep in place with perm roller)
    - Aim beam from a position caudal and dorsal to the film; this will “push” the teeth onto the image, using the tape roll to assist (Fig. 4-28)
  - Maxillary premolars of cats and brachycephalic dogs
    - Keep mouth open with clear mouth gag, place sensor/film under the maxillary premolars on the down side, slightly dorsal to the teeth (Fig. 4-29)
    - Aim beam from above and caudally, at a slight oblique, so the image of the “down-side” maxillary premolars will be projected on the film underneath (follow the beam), and the “up-side” maxillary teeth will not be superimposed (Fig. 4-30). Note or mark the film as extraoral for later identification purposes.
    - Note: since the beam is further from the film than in an intraoral method, additional exposure time may be necessary.

Figure 4-3 Three tools to help with taking radiographs: spiral perm roller for keeping sensor/film in place; two tongue depressors attached with a pushpin; and roll of tape.

Figure 4-4 The embossed dimple on the film helps in positioning the film for tooth identification.

Figure 4-5 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 4-6 Parallel placement of an intraoral film to image the mandibular premolars and molars, as demonstrated on this cat skull. Note that the corner is pushed into the intermandibular space.