Feline Odontic Resorptive Lesions (Cavities)

feline odontoclastic resorptive lesions




Cats usually don’t get dental cavities in the same way humans do, however, a very common problem in cats is a condition known as feline odontoclastic resorptive lesions (FORL)  tooth resorptive lesions or cervical line lesions. These are extremely painful lesions which are estimated to occur in between 20-67% of cats.

The cause isn’t known, although diet is thought to be a risk factor and the condition is are sometimes seen in conjunction with gum disease. Lesions usually begin under the gingival margin and are caused by odontoclasts which are cells who’s role is to absorb the bone and roots of deciduous (baby) teeth. In the case of FORL, these cells reabsorb the adult teeth.

Lesions fall into three categories:

  • Internal resorptive lesions – Lesions begin in the inner structures of the tooth and don’t become apparent until they work their way to the outside.
  • External ondoclastic resorption – These lesions begin at the cementoenamel junction (neck of the tooth). The most commonly affected tooth is the third premolar on the lower (mandible) jaw, followed by the first molar, but any tooth can be affected.
  • Cervical line erosions – Occurring along or just above the gum line on the teeth.

The condition is staged according to the amount of destruction to the affected tooth/teeth.

Stage 1 – There is an erosion of the enamel. The root and periodontal ligament are normal. Mild pain may be observed.

Stage 2 – Erosion of the enamel and dentin (bony tissue underneath the enamel).

Stage 3 – Dental tissue deep within the tooth has been lost (enamel, cementum, dentin extending into the pulp cavity). The tooth is still structurally stable.

Stage 4 – Dental tissue deep within the tooth is lost, the tooth is no longer stable.

Stage 5 – The tooth is almost entirely resorbed, with gingival tissue covering the area.

What are the symptoms of tooth resorptive lesions in cats?

  • Pain when eating, or reluctance to eat.
  • Drooling.
  • Bleeding from the mouth.
  • The appearance of gum tissues growing over the tooth or a visible hole in the tooth which is filled with granulation tissue.

Obviously, internal resorptive lesions may be harder to identify unless the lesion has made its way to the outside. This is why it is important to see your veterinarian if you notice any symptoms such as reluctance to eat or drooling as these can be a sign of an underlying problem.

How are they diagnosed?




Your veterinarian will perform a close examination of your cat’s mouth, carefully checking the teeth and gums. As resorption can occur from the inside out, visual inspection of the teeth may not always be useful. Therefore it dental x-rays may be required, this will be under general anesthesia.

How are they treated?

Treatment depends on the severity of the condition. Stage 1 FORL may be treated by applying a fluoride varnish or sealant over the tooth.

Crown amputation involves removing the tooth to the level of the gum leaving the tooth root fragments intact, the area is then covered with gum tissue.

In moderate to severe cases, removal of the entire tooth is usually recommended.




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