1. DENTAL RADIOGRAPHY Chapter 24
Credits: Unless otherwise indicated the radiographs and photographs are courtesy of Susan MacNeal, RVT, CVDT, BSc Veterinary Technician Program, Georgian College, Orillia, ON
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

2. Chapter Outline Objectives Key terms Overview Indications
Positional terminology
Tooth anatomy and dental formula
Nomenclature
Normal radiographic anatomy
When you have finished this chapter, you will be able to:
Produce diagnostic high-quality dental radiographs of the dog and cat with special emphasis on the following :
The proper dental terminology and the tooth surfaces.
The basic anatomy and formula of the teeth, including the number of roots for each tooth.
Proper viewing of dental films.
Use of parallel and bisecting angles.
The normal views and protocol for extraoral and intraoral dental radiographs, keeping in mind where to measure, center, collimate, and properly position.
Further concerns and idiosyncrasies, including the variations between dogs and cats.
Key Terms:
Indications
Part of a comprehensive oral health examination for proper diagnosis, treatment planning, and monitoring.
Oral disease is very common in dogs and cats.
Dental radiographs enable us to thoroughly evaluate the entire tooth and surrounding tissues, including bone.
Full-mouth radiographs should be taken as part of a complete oral examination.
Specific indications for radiographs include, but are not limited to:
Periodontal disease, missing teeth, resorptive lesions, oral tumors and gingival inflammation, malformed teeth, discolored teeth, dental extractions, and dental trauma.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

3. Chapter Outline Continued
Viewing and mounting dental radiographs
Projection geometry
Foreshortening and elongation
Extra-oral dental radiography
Intraoral dental radiography
Errors in film placement and artifacts
Abnormal pathology radiographs
Key points
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

4. Positional Terminology
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

5. Tooth Anatomy
The crown is above the gums (supragingival) and the root below the gums (subgingival).
The apex is the tip of the root.
At the tip of the root there are small openings to allow the blood supply and nerves to enter the tooth; these openings are referred to as the apical delta.
On a radiograph, the pulp chamber is the darker inner content of the tooth extending throughout the crown and the root.
The root portion of the pulp chamber is generally referred to as the root canal.
The dentin constitutes the bulk of the tooth and appears lighter than the pulp chamber on a radiograph.
As a patient ages, secondary dentin is continuously produced.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

6. Aging
Permission granted from Tutt D: BSAVA manual of canine and feline dentistry, 3rd ed, Gloucester, UK, 2007, British Small Animal Veterinary Association.
Over time, the pulp chamber decreases in size because of the secondary dentin.
Size of the pulp chamber evident on a radiograph of the lower first molar can help with aging of an animal.
The enamel is the outer covering of the crown, and the cementum is the outer covering of the root.
The area that they meet is termed the cementoenamel junction (CEJ).
The enamel and cementum are difficult to distinguish from the dentin.
The periodontal ligament forms the attachment of the cementum to the alveolar bone.
It appears as a thin gray line surrounding the roots.
The lamina dura is the wall of the alveolar socket that surrounds the tooth.
It appears as a dense white line adjacent to the periodontal ligament space.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

7. Dental Formula Canine
The four basic tooth types in dogs and cats are as follows:
Incisors (I or i) are used for grooming as well as grasping and cutting food. All incisor teeth are single rooted.
Canine teeth (C or c) are single-rooted teeth that are use for grasping and holding prey.
The structure of feline canine teeth support that cats are true carnivores. There are shallow longitudinal groves on the buccal surfaces of the canine teeth.
These grooves “wick” away blood from held prey.
Premolar teeth (P or p) are designed for cutting and shearing meat. Premolar teeth have prominent sharp cusps and have one to three roots.
Molar teeth (M or m) generally have flattened occlusal surfaces with the exception of the mandibular first molar tooth in dogs, which does have a cutting edge on the mesial cusp.
The first mandibular molar tooth in cats has no flattened occlusal table; instead it has two cutting edges.
Molar teeth have two or three roots, but some roots appear to be fused together to give the appearance of being single rooted (feline maxillary first molar).
Molar teeth in dogs are used for grinding food.
Canine Dental Formula
Deciduous teeth: 2  (i3c1p3m0/i3c1p3m0 ) = 28 in total
(shortened version to remember is 313/313
Permanent teeth: 2  (I3C1P4M2/I3C1P4M3 ) = 42 in total
(a shortened version to remember is 3142/3143 )
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

8. Dental Formula Feline Feline Dental Formula
Deciduous teeth: 2 (i3c1p3m0/i3c1p2m0 ) = 24 in total
A shortened version to remember is 313/312
Permanent teeth: 2  (I3C1P3M1/I3C1P2M1 ) = 30 in total
A shortened version to remember is 3131/3121 
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

9. Nomenclature Nomenclature
Two types of numbering systems are used in veterinary medicine for identifying teeth. The anatomical system is an older system but still used in veterinary clinics. The modified Triadan system is the current numbering system of choice. It is easily integrated into paperless records and using it is much faster than using the anatomical system once it has been learned.
Anatomical System for Notation
The anatomical system uses a combination of short forms for tooth type (I, C, P, M for permanent teeth; or i, c, p, m for deciduous teeth) and the numbers of those teeth in their group (i.e., premolars 1-4) to designate a specific tooth.
The number of the tooth is placed on the left for a left-sided tooth and the right for a right-sided tooth; the number is superscript for a maxillary tooth and subscript for a mandibular tooth.; For example, I2 designates the right maxillary second incisor (intermediate incisor).
Modified Triadan System
Use a code of 3 numbers, starting at the midpoint of the arch in each quadrant.
The first number designates the quadrant. upper right quadrant=1, , the upper left quadrant = 2, the lower left =3, and lower right =4.
Deciduous teeth use the series 5 through 8 for the quadrants.
The second two numbers =tooth position, counting back from the midline of the arch in each quadrant. Incisors are numbered 01 , 02, and 03; the canine tooth is 04; premolars are 05, 06, 07, and 08; and the molars are 09, 10, 11, . So for example, the Triadan number for 3I is 203.
The Triadan system is adaptable to any species.
Because the cat is missing the upper first premolar, there are no 105 or 205 teeth in a cat.
Cat is missing- 12P12, the numbers 305, 306 or 405, and 406 are not used.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

10. Permanent Roots Canine Feline
Image modified from Holmstrom, SE: Veterinary dentistry for the technician and office staff, St. Louis, 2000, Saunders. Elsevier
It is very important to appreciate the structure and number of tooth roots.
The appreciation of this anatomy is vital to determine tooth angle and to decide when to change the direction of the x-ray beam to isolate the roots.
It is also important in the interpretation of radiographs to recognize extra or malformed roots.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

11. Radiographic Dental Images Incisors
Adult Maxilla
Adult Mandible
Normal adult maxillary incisors and teeth:
Look for white space distal to incisors, with two oval (dark) spaces, which are the palatine fissures.
Normal adult mandibular incisors
Look for a dark black line distal to incisors that separates mandibular rami.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

12. Radiographic Dental Images Molars and Premolars
Adult Maxilla
Adult Mandible
Normal adult maxillary premolars and molars.
Look for the fine white line representing the maxillary recess apical to the roots.
Normal adult mandibular premolars and molars.
Look for dark black areas above and below the mandible.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

13. Viewing Dental Radiographs
Convex side → xray “dot”—front of mouth
White side → xray “a” at front of mouth
Convex dot at rostral mouth
Dimple raised
Maxillary cusps down / mandibular cusps up
Look at film as if looking at animal
Film is always exposed with the convex dot at the rostral end of the mouth; therefore, views on the right side have the dot in a different location from those on the left side.
Figure demonstrates with digital films how the locations of the dot (“a” on digital plates) differ.
Once the film has been developed, hold it so the convex dot is raised toward you (as it was placed in the mouth).
Determine whether you are looking at a maxilla or a mandible (see earlier discussions of tooth anatomy and normal anatomy radiographs).
Orient the radiograph so the cusps of the maxillary teeth are pointing down toward floor and the cusps of the mandibular teeth are pointing up toward the ceiling (Figure 24-13).
Look at the film as if you were looking at the animal with the film positioned in its mouth.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

14. Viewing Dental Radiographs
Proper film placement
With the convex dot facing you, visualize the film inside the patient’s mouth to determine whether the film is showing the left or right side.
The anatomical structures and orientation of the teeth will allow you to determine if it is a maxilla or mandible and left or right (figure 24-14).
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

15. Mounting and Viewing Digital Images
If a full-mouth set of radiographs is taken, the practitioner may want them organized in a film mount.
The film mount allows the films to be organized in a prearranged layout and filed for future reference.
Digital systems also have templates built into the software to mount the digital radiographs
A full-mouth set of dental radiographs should always be mounted as if you were looking at the animal.
The animal’s right side of the mouth should be on your left when viewing the full set of radiographs
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

16. Full Mouth Feline Radiographs
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

17. Projection Geometry Parallel Technique
Parallel technique involves placing the dental film directly behind and parallel to the tooth and then directing the x-ray beam perpendicular to the film.
The anatomy of dog and cat mouths allows the parallel technique to be used in only one area.
This area encompasses the teeth distal to and including the mandibular third premolars (3P3 or 307/407).
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

18. Projection Geometry Bisecting Angle
View from Front
View from Side
Bisecting Angle Technique
Because of the anatomical structure of the mouths of dogs and cats, film cannot be placed directly behind most teeth.
The bisecting angle technique is used to image these teeth.
This technique is used on all maxillary teeth, all incisors and canines, and mandibular premolars 1 and 2.
The bisecting angle is an angle formed by the intersection of the plane of the film and the long axis of the tooth.
If the central ray is perpendicular to a line that bisects this angle, the resulting image is as accurate as possible (Figure 24-18B).
In order to accurately visualize the long axis of the tooth, you should stand at the patient’s front (premolar teeth) or the patient’s side (incisor and canine teeth) to find the bisecting angle.
FIGURE
A, Radiograph setup for maxillary premolars (lateral recumbency). Note: You must be at the front of the patient to appreciate the angle that the tooth enters the skull. B, Radiograph setup for mandibular incisors (lateral recumbency). Note: You must be at the side of the patient to appreciate the angle that the tooth enters the skull.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

19. Foreshortening and Elongation
If the x-ray beam is not aimed directly at the bisecting angle, the image will not be a true representation of the tooth. An artifact: elongation, or foreshortening will result.
The analogy of using the shadows created by the position of the sun overhead is one way to explain elongation and foreshortening.
Think of the sun as it creates shadows on objects.
When the sun is coming up on the horizon, a very long shadow is created; this effect is elongation.
At noon the sun is overhead, and your shadow is smaller than you are; this effect is foreshortening.
Elongation is the result of the central ray’s being at a right angle to the long axis of the tooth instead of to the bisecting angle.
Because the beam is directed at the angle of the tooth., the image will appear “stretched out,” and the entire tooth may not have been captured on the film.
Foreshortening is the result of the central ray’s being at a right angle to the film instead of to the bisecting angle.
Because the beam is directed at the angle of the film, the tooth will appear to have the crown overlapping on the root.
Technician Notes:
If the beam is perpendicular to the film the image would be foreshortened.
If the beam is perpendicular to the root, the image would be elongated.
If you split the difference the image is truer.
The bisecting angle is splitting the difference.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

20. Remember Your Checklist
Settings, image receptor, correct body part, center, and borders correct, collimate
ID placement:
Measure:
Angle of ray:
Parallel or bisecting technique:
As with your other positions, quickly go through your mental checklist before pushing the exposure button; the checklist includes the following items:
Settings correct
Image receptor/machine in position
Proper location of markers and identification (ID) (if using at this stage)
Properly centered on correct tooth/teeth
Borders correct and collimated
Patient properly positioned, ID (if film used) is in the field of view but not obliterate important structures
Measure at the correct area
Always have central ray at the area of interest and the correct angle
Parallel or bisecting technique
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

21. Extraoral Dental Radiography
Teeth
View
Maxillary Premolars and Molars
Right VD Oblique
Left VD Oblique
Mandibular Premolars and Molars
Right DV Oblique
Left DV Oblique
Maxilla Incisors and Canine
DV Intraoral/ Occlusal
Mandible Incisors and Canine
VD Intraoral/ Occlusal
The use of conventional cassettes is not the ideal way to image teeth, but if there is no dental x-ray machine or nonscreen film, it is the only option.
See the discussion of intraoral radiography with conventional machine later in this chapter.
Screened cassettes and radiolucent positioning devices are required.
Difficulties expected include:
positioning of the cassettes in the mouth, because of the general characteristics of cassettes (size, thickness, weight).
Teeth in the distal aspect of the mouth may be difficult to image owing to superimposition of the contralateral arch.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

22. Maxillary Premolars and Molars VD Oblique Extraoral Views
MEASURE:
Caudal hard palate at commissure of lips.
CENTRAL RAY
Maxillary third premolar.
INCLUDE :
Maxillary premolars and molars.
POSITIONING
Position the patient in lateral (side) recumbency, affected side down on the cassette; then rotate the patient so it is placed midway onto its back, between the lateral and ventral-dorsal (ventrodorsal [VD]) positions.
Place the mandible on a foam wedge, rotating the mandible at a45-degree angle with the table surface.
The mouth should be wide open with a radiolucent mouth gag in place.
Comments and Tips:
Make sure the contralateral maxillary teeth and roots do not superimpose against interested maxilla premolars and molars.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

23. Mandibular Premolars and Molars DV Oblique Extraoral Views
Mandibular Premolar and Molars: Dorsoventral Oblique Extraoral Views
MEASURE:
Thickness of mandible at the commissure of lips
CENTRAL RAY:
Site of interest.
INCLUDE:
Mandibular premolars and molars.
POSITIONING
Position the patient in lateral recumbency with the affected side down on the cassette.
Place the maxilla on a foam wedge, rotating the maxilla at a 20-degree angle with the table surface.
The mouth should be wide open with a radiolucent mouth gag.
Comments and Tips :
Make sure the contralateral mandibular teeth and roots do not superimpose over the areas of interest, which are the mandibular premolars and molars.
 The contralateral mandibular premolars and molars appear whiter because of the bone superimposition.
The affected side’s premolars and molars appear magnified because of the angle of the head (causing elongation).
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

24. Maxillary Incisors and Canine DV Intraoral Occlusal View
Maxilla Incisors and Canine: Dorsoventral Intraoral/Occlusal View
MEASURE:
At the level of the commissure of the lips (maxilla thickness).
CENTRAL RAY:
Site of interest.
INCLUDE:
All incisors and canines, including roots.
POSITIONING
Position the patient in sternal recumbency.
A foam sponge should be placed under the mandible and cassette to keep it parallel to table top. Place one corner of the film cassette into the mouth as far as possible.
Comments and Tips:
Source-image distance (SID) will have to be adjusted because of the raised cassette. The roots of the canine teeth will be superimposed over the premolars distal to the canine tooth The rostral nasal sinus cavity can be assessed with this view.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

25. Mandibular Incisors and Canine VD Intraoral Occlusal View
MEASURE:
At the level of the commissure of the lips (mandible thickness, which is1M1 in dogs).
CENTRAL RAY:
Site of interest.
INCLUDE:
All incisors and canines, including roots.
POSITIONING
The patient should be positioned in dorsal recumbency with a foam sponge placed under the nose and cervical spine to keep the mandible and cassette parallel to the tabletop.
Place one corner of the film cassette into the mouth as far as possible.
Comments and Tips:
Raise the tube head, because the SID has decreased. The mandibular canine tooth will be slightly superimposed over the first premolar.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

26. Intraoral Dental Radiography
Lateral recumbency
Mandible/maxilla
Parallel with table
Watch tongue/ET
SID varies
Film size and teeth
Center on the tooth
Convex dot
Use proper angle
The size of film:
general, size 4 film should be used for all x-rays of the canine teeth except for small dogs and cats.
Most views in cats utilize size 2 films.
The following views are demonstrated with the patient in lateral recumbency- greatly reduces moving the patient during anesthesia.
The mandible and maxilla should be kept parallel with the tabletop.
Use a small roll or foam wedge I
Tie ET out of the way
Use a paper towel to position the film in the mouth.
The distance between the cone and the film depends on the size of film used.
Sizes 0, 1 or 2 –place cone against the patient’s face -(SID) of 1 to 2 inches.
Size 4 –increase SID -at least 6 inches to allow for a wider area of x-rays
Increase exposure if SID increased.
Rule of thumb- distance ~6 inches from the film, ↑ exposure 1.5 X normal (inverse square law)
Digital systems may not need ↑ exposure because of the greater sensitivity of digital plates .
Always center the cone on the tooth in question.
Dental x-ray machines have no collimator light; therefore the direction and width of the x-ray beam must be estimated with applicator sticks.
Remember that once the beam leaves the collimator cone, it gets wider the farther it must travel.
Also remember that the “dot” should be rostrally placed with the convex side of the film (white side) facing the tube head (“a” on digital plates).
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

27. Canine Maxillary Premolars
FILM:
The opposite edge of the film should be touching the hard palate, resting against the palatal surface of the contralateral teeth.
The tips of the premolar/molar should be at the edge of the film closest to the cone to allow ample space for the roots of the tooth to “fall onto” the film.
A size 2 film is likely necessary to capture distal molars because of anatomical space constraints.
CENTRAL RAY:
The cone is directed laterally and centered over the tooth in question. The SID depends on the size of film. For a size 4 film, the SID is 6 inches.
ANGLE:
The bisecting angle is found by standing at the patient’s front.
TECHNICIAN NOTES
When placing the film packet inside the mouth, remember, “the white side faces the white teeth” and the dot should be at the front of the mouth.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

28. Canine Maxillary Premolars SLOB Rule
Same Lingual Opposite Buccal
(108 [P4] or 208 [4P]) = 3 rooted tooth - one large distal root and two smaller mesial roots.
The mesial roots superimpose over each other if the beam is directed from the lateral aspect.
If a desired root needs to be isolated, the direction of the beam can be directed from the mesial or the distal aspect to “split” the roots on the film.
The SLOB rule stands for “same lingual opposite buccal.”
This term is used to help identify the particular root when the beam is directed from the mesial or distal aspect.
“Same lingual” means that the lingual-mesial root (which is actually the palatal root - maxilla) appears to move in the same direction as where the x-ray beam is being directed from.
“Opposite buccal” means that the buccal-mesial root appears to move in the opposite direction from where the x-ray beam is coming from.
The SLOB rule can be illustrated using your hands as shown in this diagram;
The root structure of 208 or 4P is depicted.
In the first diagram, you can see the thumb and one finger.
In the second diagram, you can see an additional finger.
If the direction the beam is coming from is changed, you will be able to see objects that were superimposed from the initial view.
In the second diagram, you can see that if the beam (your eyes) is directed from the distal aspect, the palatal root appears to move in the same direction as where the beam is being directed from.
If the beam is directed from the distal aspect, the palatal root will appear as the middle of the three roots on the radiograph.
If the beam is directed from the mesial aspect, the buccal root will appear as the middle of the three roots on the radiograph.
Think of also looking at a 3 legged stool from the different angles.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

29. Canine Maxillary Premolars SLOB Rule
Set up as per maxillary premolars and molars
Change the beam direction
Need both a lateral and an oblique to isolate 3 roots of 4th premolar
A, Initial set up for imaging fourth maxillary premolar as viewed from patient’s side B. Mesiolateral oblique radiograph setup of maxillary fourth premolar (lateral recumbency). showing final oblique x-ray cone. ( note the beam comes from the rostral direction) C. , Distolateral oblique radiograph setup of maxillary fourth premolar (lateral recumbency) showing final oblique x-ray cone. – note: The beam comes from the caudal direction.
Technique
The same setup for the film, cone, and bisecting angle are used as described previously for maxillary premolars and molars is used as the starting point.
Once the bisecting angle is found and the cone is aimed perpendicular to it from the lateral aspect, the cone can be directed from the mesial or distal aspect.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

30. Canine Maxillary Premolars SLOB Rule
Mesiolateral Oblique
Distolateral Oblique
FIGURE Mesiolateral Oblique View
For the mesiolateral oblique view, the cone is directed from the mesial aspect (mesial to distal), approximately 30 degrees from the initial position.
This shows the mesial roots isolated on the radiograph.
However the distal root will superimpose over the first maxillary molar tooth.
The central root is the mesial-buccal root.
FIGURE 24-31: Distolateral oblique radiograph
For the distolateral oblique view, the cone is directed from the distal aspect (distal to mesial), approximately 30 degrees from the initial position
However, the mesial roots may superimpose over the third maxillary premolar tooth.
The central root is the mesial-palatal root.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

31. Canine Maxillary Canine Tooth
FIGURE: Three views of the intraoral technique radiograph setup of the maxillary canine tooth (lateral recumbency): view from the patient’s side to aim at bisecting angle (A)and view from front while finding bisecting angle , (angle meter should be at 0 degrees) (B) view from the patient’s front after final tilt (30 degrees) of x-ray cone) (C)and the radiograph (of the maxillary canine tooth. Note: ipsilateral incisors can be imaged as well (D)
The radiograph of the maxillary canine tooth is set up using the long axis of the tooth, which can be visualized from the side of the patient;
Then the x-ray cone is directed in an oblique angle toward the midline of the animal.
Change in beam angle helps prevent superimposition of the canine tooth over the premolar teeth.
The canine tooth curves distally, with its apex typically over the root of the second premolar; always use the root of the tooth to find the bisecting angle, not the crown.
This view can also be used to visualize the ipsilateral incisors.
When changing the beam angle it is helpful to utilize the angle meter on the tube head.
With an animal in true lateral recumbency the angle should be on zero degrees. 
FILM: Size 4 film is used for most dogs. Both canine teeth should be touching the film (“biting on it”). The tip of the canine tooth desired should be at the lateral edge of film to allow ample space for the root of the canine to “fall onto” the film.
CENTRAL RAY: The film to cone distance ~ 6 inches for a dog’s canine tooth.
The cone is directed in a rostrocaudal direction and centered over the tooth in question.
The angle meter should read 0 on the tube head if the animal is in true lateral.
The tube head is then moved up approximately 30 degrees vertically from the starting point so that the canine tooth does not superimpose over the premolars distal to it.
ANGLE: Find the bisecting angle of the tooth by standing at the patient’s side using the long axis of the tooth.
If root cutoff occurs and both canine teeth are “biting” on film, you need to foreshorten the angle slightly. To foreshorten the angle, focus more on the film.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

32. Canine Maxillary Incisors
The typical rostrocaudal view can capture all the incisors on one film.
Because they converge at the midline, the roots cannot always be isolated because they may overlap slightly.
In some instances, if a specific incisor needs to be isolated, the x-ray cone can be directed obliquely from the left or right side so its root is more isolated (similar to technique for maxillary canine tooth).
Elongation is a common artifact for this view.
Dog incisors have long roots that curve distally, like the root(s) of a canine tooth.
FILM:
The tips of the incisor teeth should be at the rostral edge of the film to allow ample space for the roots of the incisors to “fall onto” the film. The canine teeth will both be in contact with the film if a size 4 film is used.
CONE:
The cone is directed in a rostrocaudal direction and centered over the nose.
ANGLE:
The bisecting angle is found by standing at the patient’s side. Remember that the incisor teeth in dogs curve distally. 
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

33. Canine Mandibular Incisors
The typical rostrocaudal view can capture all the incisors on one film.
Because they converge at the midline, the roots cannot always be isolated because they will overlap slightly. In some instances, if a specific incisor needs to be isolated, the x-ray cone can be directed obliquely from the left or right side so its root is more isolated (similar to mandibular canine tooth).
Elongation is a common artifact for this view. Dog incisors have long roots that curve distally like the root(s) of a canine tooth.
FILM:
The tips of the incisor teeth should be at the rostral edge of the film to allow ample space for the roots of the incisors to “fall onto” the film. Both canine teeth will be in contact with the film if a size 4 film is used.
CENTRAL RAY:
The cone is directed in a rostrocaudal direction and centered over chin.
ANGLE:
The bisecting angle is found by standing at the patient’s side.
Remember that the incisor teeth in dogs curve distally.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

34. Canine Mandibular Canine Tooth
Visualize the long axis of the tooth from the side of the patient.
Then slightly direct x-ray cone in oblique angle toward the midline of the animal.
Change in beam angle helps prevent superimposition of the canine tooth over the premolar teeth.
When changing the beam angle, utilize the angle meter on the tube head.
With an animal in true lateral recumbency the angle should be on zero degrees.
Mandibular canine teeth converge towards midline therefore the angulation toward midline is less than required for the maxillary canine tooth.
FILM:
Size 4 film is used for most canine teeth.
Both canine teeth should be touching the film (“biting on it”).
The tongue is positioned on the opposite side of the film.
The tip of the canine tooth desired should be at the lateral edge of the film to allow ample space for the root of the canine to “fall onto” the film.
CENTRAL RAY:
The film-to-cone distance should be about 6 inches for a dog’s canine tooth.
The cone is directed in a rostrocaudal direction and centered over the tooth in question.
The angle meter should read 0 on the tube head if the animal is in true lateral.
The tube head is then moved up approximately 15 degrees vertically from the starting point so that the canine tooth does not superimpose over the premolars distal to it.
ANGLE:
The bisecting angle of the tooth is found by standing at the patient’s side using the long axis of the tooth. If root cutoff occurs and both canine teeth are “biting” on the film, you need to foreshorten the angle slightly. To foreshorten the angle, focus more on the film
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

35. Canine Mandibular Premolars 1 and 2
Parallel technique cannot be used on mandibular premolars 1 and 2.
Dogs have an elongated mandibular symphysis, which makes correct film placement impossible.
Bisecting angle technique must be used on these teeth.
FILM:
The film (size 2) should be resting on both first and second premolars (left and right), behind the canine teeth, facing the floor of the mandible. The tips of the premolars to be radiographed should be at the edge of film closest to you (lateral) to allow ample space for the roots of the tooth to “fall onto” the film.
CENTRAL RAY:
The cone is directed laterally and centered at the tooth to be radiographed.
ANGLE:
The bisecting angle is found by standing at the patient’s front.
The x-ray beam will be angled through the floor of the mandible.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

36. Canine Mandibular Premolar 3,4/Molars (Parallel Technique)
Parallel technique can be used for the mandibular premolars 3 and 4 and the mandibular molars.
No hard palate to interfere with film placement behind their roots.
FILM:
The film is placed between the tongue and the mandible, parallel to the long axis of the teeth.
It is necessary to push the film down until you can feel the film pop out under the ventral mandible.
This maneuver ensures that the entire tooth is captured.
A paper towel can be used to keep the film pushed down.
The film can be gently bent to accommodate placement, and if a larger film is used, it can be placed behind the tooth diagonally so it fits.
CENTRAL RAY:
The cone is directed laterally and centered on the tooth to be radiographed, perpendicular to film.
ANGLE:
Parallel technique.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

37. Feline Maxillary Premolars Intraoral
Intraoral -modified parallel technique
The standard bisecting angle that is traditionally used for maxillary premolars in a dog cannot be used for feline teeth.
Zygomatic arch will be superimposed on these teeth.
A “modified parallel technique” is used to minimize this superimposition.
It is very important that the beam is perpendicular to the film from the front and side when using the modified parallel technique for the feline intraoral maxillary premolars.
FILM:
The top edge of the film (size 2) is resting against the palatal aspect of the maxillary premolar teeth on the side of mouth opposite to the teeth you are imaging.
The bottom edge of the film rests against the lingual aspect of the mandibular canine tooth on the side of the mouth you are radiographing.
The tongue should be behind the film on the mandible.
The endotracheal tube will be on the tube side of the film.
It may have to be untied and secured on one side only (with hemostats clamped to fur) for this view.
The maxillary arcade should be parallel to the tabletop.
CENTRAL RAY:
The x-ray cone is directed perpendicular to the film visualized from the front and ventral aspect of the patient.
ANGLE:
The angle is referred to as a modified parallel technique.
It is very important that the beam is perpendicular to the film from the front and side.
NOTE: If root cutoff occurs, the beam must be centered more on the roots of the teeth.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

38. Feline Maxillary Premolars Extraoral
Extraoral technique is preferred technique if a direct digital radiography(DDR) sensor is used:
Using standard technique with the bulky sensors is problematic.
POSITION:
The cat should be positioned in lateral recumbency with the mouth propped open.
A 1-mL syringe (cut down) can be used to prop the mouth open.
The endotracheal tube should be gently pulled ventrally so it is not superimposed over the premolars.
FILM:
Size 2 film is positioned extraorally under the side to be radiographed.
The cusps of the premolars should be at the edge of the film, allowing ample space for the roots of the teeth to be imaged (most of the maxilla should be on the film). The film must be parallel to the roots of the premolars; a small roll of tape or foam wedge under the film can be used to position it.
CENTRAL RAY:
As a starting point, with the patient in lateral recumbency the cone is aimed at both maxillary arcades as if to superimpose them on the radiograph.
Then the cone is directed toward the film, centering at the roots of the premolars near the film and bypassing the opposite arcade.
ANGLE:
The beam is aimed at the film in a “near-parallel” technique.
Comments and Tips
On the radiograph, you will see the premolars on the opposite side but they should not be superimposing on the maxillary premolars in question.
The film will have to be identified properly because the extraoral technique was used.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

39. Feline Maxillary Canine
The radiograph of a maxillary canine tooth in a cat is set up using the long axis of the tooth, which can be visualized from the side of the patient;
Then the x-ray cone is directed in an oblique angle toward the midline of the animal.
Helps prevent superimposition of the canine tooth over the premolar teeth.
The canine tooth curves distally but not in as pronounced a way as the same tooth in a dog.
When changing the beam angle it is helpful to utilize the angle meter on the tube head.
With an animal in true lateral recumbency the angle -on zero degrees. 
FILM:
Size 2 film is used.
Both canine teeth should be touching the film (“biting on it”).
The tip of the canine tooth desired should be at the lateral edge of film to allow ample space for the root of the canine to “fall onto” the film.
CENTRAL RAY:
The cone is directed in a rostrocaudal direction and centered over the tooth in question
The degree of angulation should read 0 on the tube head if the animal is in true lateral.
The tube head is then moved up approximately 30 degrees vertically from the starting point so that the canine tooth does not superimpose over the premolars distal to it.
ANGLE:
The bisecting angle of the tooth is found by standing at the patient’s side using the long axis of the tooth.
If root cutoff occurs even though both canine teeth were “biting on” the film, you should ensure that the beam is centered on the film, and you may need to foreshorten the angle slightly.
To foreshorten the angle, focus more on the film.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

40. Feline Maxillary Incisors
The typical rostrocaudal view can capture all the maxillary incisors on one film.
Feline maxillary incisors are similar to little “pegs”.
They curve slightly distally and do not converge in the middle like dog incisors.
FILM:
Size 2 film is used for the maxillary incisors. The tips of the incisor teeth should be at the edge of the film closest to you (rostral) to allow ample space for the roots of the incisors to “fall onto” the film.
CENTRAL RAY:
The cone is directed in a rostrocaudal direction and centered over the nose.
ANGLE:
The bisecting angle is found by standing at the patient’s side. 
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

41. Feline Mandibular Canines and Incisors
Both mandibular canines and all incisors of the cat can be imaged in one view. The reason is that cats are missing premolar 1 and 2, thus allowing for a rostrocaudal beam without superimposition on other teeth.
FILM:
Size 2 film is used. Both canine teeth should be touching the film (“biting on it”). The tongue is positioned on the opposite side of the film.
CENTRAL RAY:
The cone is directed in a rostrocaudal direction and centered over the patient’s chin.
ANGLE:
The bisecting angle is found by standing at the patient’s side. The long axis of the canine tooth, not the incisors, should be used to find the bisecting angle. Remember that the canine tooth has a large root that curves in a caudal direction.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

42. Feline Mandibular Premolars and Molar Standard Technique
Parallel technique can be used to image the mandibular premolars and molar of the cat:
There is no hard palate to interfere with film placement behind these roots.
The mesial root of premolar 3 can be difficult to capture owing to interference with film placement and the mandibular symphysis.
A bisecting angle technique can be used to image these teeth if this problem occurs.
FILM:
The film (size 0 works best) is placed between the tongue and the mandible, parallel to the long axis of the teeth.
It is necessary to push the film down until you can feel it pop out under the ventral mandible.
This maneuver ensures that the entire tooth is captured.
A paper towel can be used to keep the film pushed down.
The film can be gently bent to accommodate placement, and if a larger film is used, it can be placed behind the tooth diagonally to fit behind it.
CENTRAL RAY:
The cone is directed in a lateral direction and centered at the tooth to be radiographed, perpendicular to film.
ANGLE:
Parallel technique.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

43. Feline Mandibular Premolars and Molar Bisecting Angle Technique
If the mesial root of the third premolar continues to be cut off and the film is placed as rostral as possible, then a bisecting angle technique can also be used to image these teeth.
If a digital radiography sensor is used, this is the preferred technique:
Film placement using standard technique with the bulky sensors is problematic.
FILM:
The film (size 2) should be resting on the floor of the mandible, preferably with the tongue on the opposite side of the film. If this is not possible, the tongue can be left between the film and the teeth.
CENTRAL RAY:
The cone is directed in a lateral direction at the tooth to be radiographed.
ANGLE:
The bisecting angle is found by standing at the patient’s front.
The x-ray beam is angled through the floor of the mandible.
 Same comment as previous in regards to DDR sensors
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

44. Canine and Feline Nasal Sinus
Indications for radiographs of the nasal sinus cavity in either the dog or cat include evaluation of disease such as neoplasia as well as the detection of foreign bodies.
POSITION:
The patient should be in sternal recumbency with the maxilla parallel to the tabletop.
FILM:
For dogs, size 4 film is inserted as far as possible into the patient’s mouth between the maxilla and the endotracheal tube. For cats, the film may need to be placed in on an angle or a size 2 film may be used.
CENTRAL RAY:
The cone is 6 to 8 inches away from the film and centered on the nasal cavity. Use settings for a maxillary canine tooth, and adjust for the distance from the film.
ANGLE:
The cone is directed perpendicular to the film.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

45. Intraoral With Conventional Unit
If a dental radiography machine is not available, the intraoral radiographs previously described can be accomplished with a conventional machine.
In the descriptions of the intraoral views,
The x-ray cone was maneuvered to focus on the bisecting angle or film where indicated.
With use of a conventional x-ray machine:
Rotate patient’s body position and skull:
Previously described angles will line up with the vertical x-ray beam.
Procedure and Supplies
Nonscreen film
Foam wedges or rolls (assortment of sizes)
SID should be 15 inches from the tabletop
Settings: kV, 100 mA, 1.6 mAs
If SID cannot be reduced, the following settings should be used:
40 inches SID, kV, 100 mA, 3.2 mAs
Any of the previously described views can be accomplished with this technique, as illustrated by two examples.
To image the maxillary premolars with a conventional machine:
The bisecting angle is found as previously described
But rotate the skull ventrally
Vertical stationary x-ray is aimed at the bisecting angle.
The mandibular incisors with a conventional machine:
The patient is in dorsal recumbency with a small foam wedge placed under the nose.
This positioning allows the vertical beam to be directed at the bisecting angle.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

46. Artifacts
A, Root cut off because of improper film placement (film not pushed in far enough).
B, Cone cut off.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

47. Artifacts C, Light exposure in chairside darkroom.
D, Film processing error: fixer not rinsed off film.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

48. Artifacts E, Fingerprints and scratches on film.
F, Bent film (crescent line).
G, Double exposure.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

49. Abnormal Pathology Top left: A, Horizontal bone loss evident on 106.
Top right: B, Vertical bone loss (arrows).
Bottom left: C, Periapical lucency on 410.
Bottom right: D, Feline resorptive lesion 407.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

50. Abnormal Pathology
Top Left: E, Ankylosis of canine mandibular premolar and molars.
Top Right: F, Congenitally missing tooth 406.
Bottom Left: G, Unerupted canine tooth 304.
Bottom Right: H, Supernumerary 105.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

51. Abnormal Pathology Top Left: I, Retained root tip 305.
J, Complete extraction of 103.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

52. Key Points Dental radiographs essential Possible in any facility
Understand and use bisecting angle
Errors with manual processing of film
SLOB rule for three-rooted teeth
1. Dental radiography is essential for a proper assessment of the oral cavity in dog and cat mouths.
2. Dental radiographs can be accomplished in any veterinary hospital, even those without a dental x-ray unit.
3. Bisecting angle technique is used in most areas of dog and cat mouths.
4. Manual processing of films can be a source of many errors.
5. The SLOB rule helps identify specific roots when the x-ray cone is directed obliquely.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

53. Mystery Radiograph
This is a digital radiograph of the mandibular premolars. The lighter half of the radiograph is due to light exposure of the plate. CR plates are very light sensitive. This artefact was created when half of the barrier envelope was torn off thus exposing one half to light while waiting to place the plate into the scanner.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

54. Remember Your Checklist
Settings, image receptor, correct body part, center, and borders correct, collimate
Label placement:
Measure at:
Measure in:
Central ray:
Parallel:
Perpendicular:
Quickly go through your mental checklist before pushing the exposure button; the checklist includes the following items:
Settings correct
Image receptor/machine in position
Proper location of markers and identification (ID) (if using at this stage)
Correct body part and view
Properly centered
Borders correct and collimated
Thickest part to the cathode – not an issue with smaller patients
Patient properly prepared, positioned, and restrained so the image will be perpendicular to the beam and parallel to the film
The label is in the field of view but not obliterate important structures
Measure at the thickest part of the area to be radiographed
Always measure the patient in the position in which it is to be x-rayed
Always have the center ray at the area of interest
Parallel and perpendicular
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.