Oral disease in cats comprises four major conditions: periodontal disease, oral neoplasia (particularly squamous cell carcinoma),
feline stomatitis and tooth resorption. Previously referred to by several terms—and recently including cervical line lesions,
resorptive lesions and feline odontoclastic resorptive lesions (FORLs)—tooth resorption is likely the most common significant
oral condition affecting feline patients.
The combined gross and radiographic occurrence of tooth resorption in random populations of clinically healthy cats ranges
from 29 to 38 percent.1-4
The number presenting to veterinary facilities primarily for dental disease is as much as twice as high.5,6
Many gross lesions are small and not readily detectable by awake oral examination alone. Magnification, immobilization and
lighting generally provide a thorough gross evaluation but will not uncover tooth resorption below the level of the marginal
bone. Therefore, dental radiography is paramount in establishing an adequate diagnosis.
Photo 1: A triangular-shaped defect in the tooth at the gingival margin (arrow) is evident. This generally occurs in Type
1 and longer-standing Type 2 tooth resorption.
One of the most useful clinical classifications of tooth resorption to date is based on the gross and radiographic description
of the lesions by type. Treatment is solely dependent on this type of classification, so, again, dental radiography is essential
in making a final determination.
Grossly, Type 1 tooth resorption is characterized by gingivitis and periodontitis generally initiated at the junction between
the cementum and the enamel. The origin is thought to be inflammatory. Cavitation defects are seen in the crown, with inflamed
gingival tissue often covering the defect (Photo 1). Radiographically, these teeth have variations in density in the crown
or root. A distinct periodontal ligament space is generally appreciated (Photo 2). Type 1 and Type 2 tooth resorption may
be observed concurrently in individual roots of a single tooth (Photo 3). Therefore, diagnostic evaluation of each root is
important to determine how each should be approached therapeutically.
Photo 2: The right mandibular fourth premolar, tooth 408 (white arrow), has a subtle crown lucency but an intact periodontal
ligament space surrounding the roots consistent with Type 1 tooth resorption. The third premolar, tooth 407 (yellow arrow),
has more pronounced crown lucency and no discernable periodontal ligament space surrounding the roots, which is typical of
Type 2 tooth resorption.
Photo 3: The left mandibular third premolar, tooth 307 (arrow), demonstrates both types of tooth resorption. The mesial root
has a periodontal ligament space consistent with Type 1 tooth resorption. The distal root has an indistinguishable periodontal
ligament space and resembles Type 2 resorption.
Type 2 (Photos 2 and 3) tooth resorption is generally thought to start at the apical half of the root. Crown involvement is
generally not noted until late in the resorption process. The hallmark of Type 2 resorption is the lack of radiographic evidence
of a periodontal ligament space surrounding the root.
Tooth roots classified as undergoing Type 1 resorption require the removal of the entire tooth root and crown by using traditional
extraction techniques (Photo 4). Tooth roots for which no periodontal ligament space is readily detected and where no periodontal
bone destruction or periapical lucencies exist may be treated by crown amputation and intentional root retention. In these
cases, a conservative periodontal flap exposes the marginal extent of the tooth (Photo 5), and a round carbide or diamond
bur on a water-cooled, high-speed handpiece is used to remove the crown and contour the bone (Photo 6) before closure with
5-0 absorbable suture (Photo 7).
Photo 4: A postoperative radiograph of the patient from Photo 2. Treatment for tooth 408 is complete extraction (Type 1).
Treatment for tooth 407 is crown amputation and intentional root retention (Type 2).
Photo 5: An example of a conservative periodontal flap. The marginal extent of tooth 307 is exposed using a periosteal elevator,
followed by crown amputation with intentional root retention for treatment of Type 2 tooth resorption.
Exceptions exist for these generalizations regarding Type 2 lesions. Some roots may require partial extractions (more significant
root remnant removal) if the periodontal ligament space is minimally detectable radiographically or abnormal tissue exists
grossly upon exposure (consider biopsy in this instance). This includes friable tooth remnants. If there's a bleeding pulp,
the entire root should be removed.
Photo 6: The radiographic appearance of tooth 307 (same patient as Photo 5) after the use of a round carbide or diamond bur
on a water-cooled, high-speed handpiece to remove the crown and contour the bone before closure.