Odontoclasts are multinucleated cells that destroy part or all of the affected tooth’s hard tissue. Odontoclastic resorption starts in the cementum (i.e., a bone-like tissue that covers the tooth root) and spreads into the dentin via dentinal tubules. The destroyed root surface is replaced by cementum. Enamel becomes involved secondary to the “caving in” of underlying dentin, creating a resorption lesion. Feline odontoclastic resorption is a common syndrome affecting cat teeth. Feline odontoclastic resorption lesions (FORLs) have been referred to as cavities, neck lesions, cervical line or neck erosions, oral or odontoclastic resorption lesions (ORLs), and external odontoclastic resorption lesions (EORLs).

1. A NEWSLETTER OF PRACTICAL MEDICINE FOR VETERINARY PROFESSIONALS
NOVEMBER 2006 VOLUME 4, NUMBER 4
Feline Odontoclastic
Resorption Lesions
Jan Bellows, DVM, DAVDC, DABVP
Hometown Animal Hospital and All Pets Dental Clinic
Weston, Florida
WHAT ARE ODONTOCLASTIC leads to reparative formation of bone or s Stage 1—Lesions extend only into
RESORPTION LESIONS? cementum-like tissue. The initial the cementum covering the root. This
Odontoclasts are multinucleated cementum resorption extends into the stage occurs subgingivally where the
cells that destroy part or all of the dentin, forming resorption channels that tooth surface is exposed to cells that
affected tooth’s hard tissue. often extend into the dentin of the can become odontoclasts. Because
Odontoclastic resorption starts in the crown. The loss of crown dentin increases there is no enamel involvement, Stage
cementum (i.e., a bone-like tissue that the fragility of the tooth and the 1 lesions are difficult to detect; they
covers the tooth root) and spreads into unsupported enamel. Alternatively, the are not radiographically apparent.
the dentin via dentinal tubules. The enamel is also resorbed. Either s Stage 2—Lesions progress through
destroyed root surface is replaced by mechanism results in the classic clinical
the cementum into the dentin of the
cementum. Enamel becomes involved presentation, a cavity filled with
root or crown but do not expose the
secondary to the “caving in” of connective tissue.
pulp. Stage 2 lesions are painful
underlying dentin, creating a resorption because dentin tubules are exposed.
lesion. Feline odontoclastic resorption CLASSIFICATION OF Hyperplastic gingiva may cover these
is a common syndrome affecting cat ODONTOCLASTIC defects. Enamel may be affected from
teeth. Feline odontoclastic resorption RESORPTION LESIONS
lesions (FORLs) have been referred to There are several systems in use to
as cavities, neck lesions, cervical line or classify resorption lesions. One method is
neck erosions, oral or odontoclastic to characterize the lesions into three ALSO IN THIS ISSUE:
resorption lesions (ORLs), and external stages: acute, chronic, and remodeling.
Another system is based on clinical
Ask the Vet ................................ 5
odontoclastic resorption lesions
(EORLs). and radiographic examination of the Intraoral Imaging Techniques..... 6
Surface resorption of root cementum FORL:

2. A NEWSLETTER OF PRACTICAL MEDICINE FOR VETERINARY PROFESSIONALS
NOVEMBER 2006 VOLUME 4, NUMBER 4
Consulting Editors
Bruce Truman
Senior Director
Animal Health and Nutrition
The Hartz Mountain Corporation
Jill A. Richardson, DVM
Director
Consumer Relations
The Hartz Mountain Corporation
Associate Editor
David Levy
Assistant Manager
Animal Health and Nutrition
The Hartz Mountain Corporation
HARTZ® COMPANION ANIMAL SM
A B
is produced for The Hartz Mountain
Figure 1. (A) Stage 2 FORL. (B) Radiograph of Stage 2 FORL. Corporation by Veterinary Learning
Systems, 780 Township Line Rd.,
Yardley, PA 19067.
odontoclasts of the periodontium or s Type 2—The affected tooth is Copyright © 2006 The Hartz Mountain
subjacent dentin (Figure 1). ankylosed to the alveolus. Type 2 Corporation. All rights reserved.
s Stage 3—Lesions progress into the lesions are not associated with Hartz® and other marks are owned by
pulp of the root canal or pulp periodontitis; instead, noninflammatory The Hartz Mountain Corporation.
chamber and are painful. Bleeding on replacement resorption results in
probing and spontaneous fracture of ankylosis (surface and/or replacement Printed in U.S.A. No part of this
the crown (enamel and dentin) can be resorption in which the bone and publication may be reproduced in any
seen (Figure 2). tooth substance become fused). form without the express written
Type 2 lesions most commonly permission of the publisher.
s Stage 4—Lesions destroy a significant
affect the mandibular third premolars
amount of the crown (Figure 3). For more information on The Hartz
(Figure 5).
s Stage 5—Lesions have significant Mountain Corporation, visit
root replacement resorption with www.hartz.com.
WHAT CAUSES FELINE
healing of the gingiva. There will not ODONTOCLASTIC
be any clinically apparent tooth tissue. RESORPTION LESIONS?
The cause of odontoclastic resorption A recent investigation of factors
Some also classify FORLs based on
is not known. Histologically, there is no controlling calcium homeostasis in cats
the radiographic appearance of the
decalcification in the dentin, suggesting with and without FORLs has shown that
periodontal ligament space:
that the resorption lesions are not similar serum hydroxy vitamin D concentration
s Type 1—Lesions are caused by to human dental caries most often caused is elevated in cats with FORLs and that
inflammation (periodontitis, by Streptococcus mutans. Theories include cats with FORLs may have been fed diets
endodontic disease). The root appears increased calcium in feline diets and with excessive vitamin D content. A
normal, and periodontal ligament abnormal pressure on the affected factor that creates abnormal formation or
space is still observable. The teeth as well as feline leukemia and mineralization of cementum could
mandibular molar is most commonly immunodeficiency disease. The etiology precipitate the development of cemental
affected (Figure 4). is unknown but is likely multifactorial. resorptions. Experimental studies of the
2 HARTZ COMPANION ANIMAL
® SM
• NOVEMBER 2006 • VOL. 4, NO. 4

3. dental effects of vitamin D toxicosis in
other species show effects similar to those
seen in cats with FORLs.
HOW ARE FELINE
ODONTOCLASTIC
RESORPTION LESIONS
DIAGNOSED?
Most affected cats do not show
clinical signs. Some cats may experience Figure 2. Stage 3 FORL. Figure 3. Stage 4 FORL.
hypersalivation, oral bleeding, or difficulty
chewing. Affected cats may pick up and
drop food (especially hard food) when
eating; others hiss while chewing.
Behavior changes, such as becoming
reclusive or aggressive, have been noted in
some cats with FORLs.
A cotton-tipped applicator applied to
the suspected FORL (Stages 2 through
4) usually causes pain evidenced by jaw
A
spasms.
FORLs can occur above or below Figure 5. Type 2 FORL.
the free gingival margin. Most occur
at the labial or buccal surface near the
cementoenamel junction where the free s Maxillary premolars and molars (two
gingiva meets the tooth surface; calculus films—one for each side)
and hyperplastic gingival tissue may s Mandibular incisors (one film)
obscure the lesion. s Mandibular canines (two films—one
FORLs can be found on any tooth;
for each side)
the mandibular third premolar and molar
s Mandibular premolars and molars
are most commonly affected, followed by
the maxillary third and fourth premolars. (two films—one for each side)
With the cat under general anesthesia,
B
lesions can be examined with an explorer; ARE ALL CATS EQUALLY
a fine Shepherd’s hook type is preferred. Figure 4. (A) Type 1 FORL of the AFFECTED?
The explorer helps identify subgingival mandibular molar. (B) Radiograph of Reported studies reveal that 20% to
lesions coronal to the alveolar bone; the Type 1 lesion with visible periodontal 72% of cats are affected with FORLs.
ligament space.
furcation area is a frequent site, and the The reported variance is related to
examiner must distinguish a resorption diagnostic methods: Some studies entail
lesion from disease limited to alveolar visual confirmation only compared with
bone loss. for cats presented for an oral assessment, others that include visual, tactile, and
The lesions can be detected through a treatment, and prevention visit. radiologic examination. Most of these
combination of visual inspection, tactile Radiographic appearance varies from studies have shown an increased
examination with a dental explorer, and minute radiolucent defects of the tooth incidence with increasing age.
radiography. primarily at the cementoenamel junction The mandibular third premolars are
Radiography will identify lesions to internal resorption and ankylosis of the the most commonly affected teeth
that are localized to the root surfaces apex to the supporting bone. (Figure 6). Often, both sides are affected.
within the alveolar bone, which may Intraoral films should include:
not be detected by clinical methods. TREATMENT
s Maxillary incisors (one film)
Consequently, radiography is required to The first step in treatment of an
diagnose FORLs. Complete survey s Maxillary canines (two films—one for odontoclastic resorption–affected tooth
intraoral radiographs are recommended each side) is proper diagnosis. Under general
HARTZ® COMPANION ANIMALSM • NOVEMBER 2006 • VOL. 4, NO. 4 3

4. compared with other ankylosed root(s) to continue fusing with
multirooted teeth. the alveolar bone.
After clinical and
tactile examination, PREVENTION
intraoral radiographs To date, there is no known proven
are taken to evaluate method to prevent FORLs. Once a
root structure and definitive etiology is determined,
involvement of the methods of prevention will hopefully be
pulp chamber. developed.
FORLs are
Figure 6. Multiple FORLs on the mandibular third premolar. considered to be SUGGESTED READING
progressive and can be
painful to the patient. Lyon KF: Odontoclastic resorptive lesions, in August JR
(ed): Consultations in Feline Internal Medicine, ed 5.
anesthesia, suspected lesions should be For Type 1 lesions in which the St. Louis, Elsevier Science, 2006.
examined with a fine Shepherd’s hook periodontal ligament is observable on Lyon KF: Subgingival odontoclastic resorptive lesions.
type of explorer. The furcation area radiographs, the recommended treatment Classification, treatment, and results in 58 cats. Vet
(where tooth roots meet) is a frequent Clin North Am Small Anim Pract 22(6):1417–1432,
is flap exposure followed by full crown
1992.
site of lesions, and the examiner must and root extraction. Type 2 lesions in Reiter AM, Lewis JR, Okuda A: Update on the etiology
distinguish between a resorption lesion various stages of ankylosis are treated of tooth resorption in domestic cats. Vet Clin North
and disease limited to alveolar bone loss either by conservative management until Am Small Anim Pract 35(4):913–942, 2005.
secondary to periodontal disease. This is the lesion penetrates into the oral cavity Reiter AM, Mendoza KA: Feline odontoclastic
resorptive lesions—An unsolved enigma in veterinary
especially true for the mandibular molar, or, preferably, by crown amputation via dentistry. Vet Clin North Am Small Anim Pract
where the furcation is distally located flap exposure and flap closure, leaving 32(4):791–837, 2002.

5. Jill A. Richardson, DVM, is Director of Consumer Relations at
The Hartz Mountain Corporation.
ASK TH E VET
Q
I have two dogs that I have been giving rawhide
for many years. I recently spoke with another
veterinarian who informed me that rawhide is
efficacy of rawhide published in the Journal of the American
Veterinary Medical Association, dogs were fed three rawhide
strips per day for 3 weeks, and no adverse effects from chewing
and/or consuming rawhide were noted.1 Also, undigested pieces
very dangerous and is made with arsenic and
of rawhide were not found in the feces of any of the study
formaldehyde. Now I am worried! Can you please dogs.
help clear this up?
What are the nutritional values for rawhide?
A
Rawhide was first introduced as a pet treat in the 1950s as
a way of satisfying a dog’s natural need to chew. Rawhide
can provide the chewing satisfaction that dogs crave and,
when used daily, can also effectively remove plaque and
Rawhide is approximately 80% to 85% protein, 10% to 12%
fiber and moisture, and 1% to 2% fat. Rawhide is not
considered a food item, but for those counting calories, rawhide
has about 130 calories per ounce.
tartar. You may find the following information about
How does rawhide help keep teeth clean?
rawhide useful. Dogs have a natural instinct for chewing. Giving a dog rawhide
treats to chew helps keep their teeth and gums healthy. The
What is rawhide? abrasive action of rawhide chewing helps reduce plaque and
Rawhide is simply the inner layer of cattle hide. During calculus. Rawhide also provides the necessary chewing exercise
processing, cattle skin is split into an inner and an outer layer. to strengthen gums and is a great way to relieve boredom,
The outer layer is tougher and is used in the leather industry for frustration, or anxiety.
such items as shoes and clothing. The inner layer is softer and is
formed into various shapes for dog rawhide chews. Since it is How effective is rawhide at cleaning a dog’s teeth?
made from cattle hide, rawhide is not recommended for animals Rawhide has been shown to be an effective way of decreasing
with beef allergies. plaque and calculus formation. In fact, according to a study,
rawhide effectively decreased plaque by 25% when given daily
How is Hartz® rawhide manufactured? as a treat.1
The inner layer of the hide comes in raw and is cleaned with Rawhide coated with HMP (hexametaphosphate) is even
a food-grade prewash. It is later treated with food-grade more effective at reducing tartar formation on dogs’ teeth than
whitening and antibacterial agents. Afterward, it is rinsed regular rawhide. HMP is classified as a food additive and works
thoroughly and rolled through a ringer. It is then formed into by interfering with the mineralization of plaque, thereby
shapes and oven dried. To ensure the highest quality and preventing accumulation and tartar formation. It can also help
sanitation, samples of the product are tested before, during, and soften and remove existing tartar. According to a study by
after the process by members of the Hartz Quality Control Hartz, when dogs chewed rawhide coated with HMP, plaque
Team. was decreased up to 83%.2
Arsenic, formaldehyde, or other dangerous chemicals are not
used in processing Hartz rawhide. What is the difference between basted and infused
rawhide?
How safe is rawhide? Basted rawhide has flavor coating on the outside of the rawhide.
The Hartz Mountain Corporation prides itself on providing the Infused rawhide has flavor infused throughout. Infused rawhide is
highest quality rawhide. As previously stated, testing of rawhide produced using a patented process in which chicken stock is
takes place before, during, and after the production process. Quality infused throughout the entire hide to increase the flavor and entice
control continues through product monitoring and inspection. dogs to chew longer. According to a Hartz study, dogs prefer
Rawhide is considered highly digestible. In a study on the infused rawhide 20 to 1 over unflavored rawhide.
(continues on back cover)
Additional newsletters may be obtained by contacting us at feedback@hartz.com or by phone at 800-275-1414.
HARTZ® COMPANION ANIMALSM • NOVEMBER 2006 • VOL. 4, NO. 4 5

6. Intraoral Imaging Techniques*
IMAGE FIELD AND FILM PLACEMENT PATIENT POSITIONING
Figure 1. Projection
for maxillary incisors. (A)
The tubehead should be
centered over the upper
incisors. The arrow depicts
the angle of the primary x-
ray beam. Size 2 film is
recommended for viewing Film
all of the upper dentition to
the level of the first
premolar. Size 4 film can
also fit in a cat’s mouth if
preferred. (B) The cat’s head
should be placed in ventral
recumbency with a small roll
inserted under the chin to A B
keep the hard palate
parallel to the table top. Size 2 or 4 intraoral film can then be placed below the incisors and canine teeth. The x-ray cone should be directed downward at
an angle of 60˚ to the horizontal plane or the hard palate. The primary x-ray beam will be almost perpendicular to the bisecting plane.
Figure 2. Lateral
oblique projection for
maxillary canine teeth. (A)
The tubehead should be
centered over the upper
canine tooth and adjacent
premolars. The arrow depicts
Film
the direction of the primary
x-ray beam. Size 2 intraoral
film is recommended for
cats. (B) The cat’s head
should be placed in ventral
recumbency and a roll
positioned under the jaw to
keep the hard palate parallel
to the table top. Size 2 A B
intraoral film can then be
placed under the canine tooth and premolars. The x-ray cone should be horizontally directed at an angle of 45˚ as shown and tipped downward at an angle
of 45˚ to 60˚ to the horizontal plane of the hard palate. The primary x-ray beam will be almost perpendicular to the bisecting plane.
Figure 3. Projection
for maxillary premolars
and molar. (A) The
tubehead should be centered Film
over the side of the cat’s face
just below the lateral
canthus. The mesial edge of
the cone is near the medial
canthus, and the distal edge
of the cone is at the base of
the ear. The arrow depicts
the direction of the primary
x-ray beam. Size 2 or 4
intraoral film can be used to
A B
view the entire upper lateral
dentition. (B) The cat’s head should be placed in ventral recumbency and a small roll inserted under the neck to keep the hard palate parallel to the table
top. Size 2 or 4 intraoral film can then be placed under the hard palate. The x-ray cone should be directed downward at an approximate angle of 30˚ to the
horizontal plane of the table top or hard palate to minimize superimposition of the zygomatic arch. The primary x-ray beam should not be perpendicular to
the bisecting plane.
*From: Intraoral imaging techniques, in Mulligan TW, Aller SA, Williams CA: Atlas of Canine & Feline Radiography. Yardley, PA, Veterinary
Learning Systems, 1998, pp 27–44. The book can be purchased online at www.vlsstore.com or by calling 800-426-9119.
6 HARTZ COMPANION ANIMAL
® SM
• NOVEMBER 2006 • VOL. 4, NO. 4

7. IMAGE FIELD AND FILM PLACEMENT PATIENT POSITIONING
Figure 4. Projection
for mandibular incisors
and canine teeth. (A) The
tubehead should be centered
over the lower incisors. The
arrow depicts the direction
of the primary x-ray beam.
Size 2 intraoral film is
recommended for
radiographs of the entire Film
lower dentition to the canine
teeth; however, size 4 film
can be used if preferred. (B)
The cat’s head should be
positioned in dorsal
recumbency and a small roll A B
inserted under the neck to
keep the hard palate parallel to the table top. Intraoral film can then be placed below the incisors and canine teeth. The x-ray cone should be directed at an
approximate angle of 60˚ to the horizontal plane of the hard palate or table top. The primary x-ray beam will be almost perpendicular to the bisecting angle.
Figure 5. Lateral
oblique projection for
mandibular canine teeth.
(A) The tubehead should be
centered over the mandibular
canine tooth. The arrow
depicts the direction of the x-
ray beam. Unlike oblique
projection in dogs, the
premolars and canine teeth
do not usually become Film
superimposed for radiographs
of cats. The view shows the
interdental (interproximal)
bone of the canine tooth and
third premolar. Size 2 A B
intraoral film is
recommended. (B) The cat’s head should be placed in dorsal recumbency and a roll positioned under the neck to keep the hard palate parallel to the table top.
Size 2 intraoral film can then be placed under the canine tooth and third premolar. The x-ray cone should be directed toward the interproximal space of the
lateral incisor and canine tooth as shown and tipped downward at an angle of 45˚ to 60˚ to the hard palate. The primary x-ray beam will be almost perpendicular
to the bisecting plane. Gauze sponges can be used to stabilize the film in the back of the mouth. All sponges and the film should be removed at the same time.
Figure 6. Lateral
projection for mandibular
premolars and molar
(parallel technique).
(A) The tubehead should
be centered over the
mandibular premolars and
molar. Size 2 intraoral film is
recommended. (B) The cat’s
Film
head should be placed in
lateral recumbency and a
spacer inserted under the
jaw to keep the hard palate
perpendicular to the plane
of the table top. Size 2
intraoral film can then be A B
placed in the vestibule
between the tongue and mandible, making sure that the film does not traumatize the symphyseal area during insertion and removal. The x-ray cone should
be positioned perpendicular to the film and teeth at an angle of about 60˚ to the horizontal plane or table top. The primary x-ray beam will be almost
perpendicular to the film and teeth.
HARTZ® COMPANION ANIMALSM • NOVEMBER 2006 • VOL. 4, NO. 4 7

8. ASK THE VET (continued from page 5)
Which Hartz products have the Veterinary Oral Health • Braided rawhides—Longer lasting and have the stick shape that
Council acceptance seal? dogs love.
The Veterinary Oral Health Council (VOHC) exists to recognize
• Twists with two different flavors—Provide twice the flavor
products that meet standards of plaque and calculus retardation in dogs
and are longer lasting than plain strips.
and cats. Products are awarded the VOHC Seal of Acceptance following
review of data from trials conducted according to VOHC protocols. The • Munchy rawhide treats—Quick crunchy treats that are great
Veterinary Oral Health Council has given its seal of acceptance to the for senior pets because they are easier to chew.
Hartz® Chew-Dent™ Infused Rawhide product for dogs.
• Long rawhide rolls—Dogs enjoy “fetching” these like they
would a stick.
How do you choose the appropriate rawhide for a dog?
There are many shapes and flavors of rawhide available on the • Pressed rawhides—Made from layers of rawhide skin pressed
market. Choosing rawhide with HMP will help provide better dental together by a machine; these are great for very aggressive
benefits. Also, dogs with tendencies for food aggression should be chewers, as the rawhide is compressed and keeps the dog
given any treat, including rawhide, cautiously and never in the chewing longer.
presence of other animals.
How can I learn more about rawhide and dental
The following quick guide can help you choose the correct treat for care for dogs?
your pet: If you would like to receive copies of the Hartz® Dental Brochures
and free samples of Hartz® Dental rawhide products, you can call
• Pencil-shaped rawhides—Smaller dogs like to chew on one
800-275-1414 (9 AM to 5 PM EST) or email dental@hartz.com.
end while holding the other end with their paws. The pencil tip
helps clean teeth when the dog chews on it.
• Bone-shaped rawhides—Last longer than sticks or chips. REFERENCES
Thicker bones can keep a dog chewing longer. 1. Effect of chewing rawhide and cereal biscuit on removal of dental calculus
in dogs. JAVMA 197(2):213–219, 1990.
• Chips—Quick chewy treats that can be given as rewards. The chips 2. Effect of sodium hexametaphosphate on dental calculus formation in
are usually eaten more quickly than the bone-shaped rawhides. dogs. Am J Vet Res 56(7):913–918, 1995.
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