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Feline Odontoclastic Resorptive Lesions (FORL)

Cats have a unique dental disease called feline odontoclastic resorptive lesions (FORL), also known as neck lesions, cervical line erosions, and cat cavities. This is an inflammatory disease process whereby the tooth actually resorbs, often at or below the gum line, and eventually breaks. Studies worldwide have shown incidence rates of over 50 percent! According to information presented at the American Veterinary Dental Forum, if your cat is over five years old, there is a 72 percent chance he or she has symptoms of this painful oral disease.

FORL, once called cat cavities or neck lesions, can occur in any tooth. The most commonly affected teeth are the lower premolars. Feline odontoclastic resorptive lesions are painful. Clinical signs associated with FORL include drooling, bleeding around the affected tooth (or teeth), and difficulty chewing. Many cats do not exhibit these clinical symptoms; however, they are uncomfortable and in pain.

An oral examination of the cat's mouth sometimes reveals a cherry-red inflammation of the gums surrounding the affected tooth (teeth). FORL can also be demonstrated by gently rubbing the suspected lesion with a cotton-tipped applicator (such as a cotton swab). If the lesion is present, pain and jaw spasms occur when the area is touched.

Specifically, the lesion contains numerous cells called odontoclasts. Odontoclasts function to resorb tooth structure. What triggers this disease is yet to be fully understood but may be diet related, associated with other viral diseases, and/or precipitated by inflammation of the gums associated with dental plaque buildup.

FORL have been classified into 5 categories:

Class 1 lesions are erosions in the enamel. At this stage, the affected tooth is not very sensitive.

Class 2 lesions are erosions in the enamel that penetrate into the dentin.

Class 3 lesions extend into the pulp chamber. At this point, the lesion is very painful. Since the pulp is exposed, bacteria can enter the tooth, causing a secondary abscess to develop.

Class 4 and 5 lesions involve varying degrees of crown destruction. This stage is extremely painful and often requires extraction of the crown and/or root fragments.

Examining your cat's mouth on a regular basis is important in detecting FORL in its early stages. If suspicious lesions are detected, a trip to your veterinary hospital is strongly recommended.

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