Feline Odontoclastic Resorption Lesions (FORLS) in Cats

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3 min read

Key takeaways

Feline Odontoclastic Resorptive Lesions (FORLs) are a condition of unknown origin where a cat’s tooth erodes.

  • Teeth exhibiting FORLs gradually become brownish-red as the enamel erodes and exposes the sensitive tissue underneath
  • Resorption progresses from root to crown, leaving only a small bump in the cat’s gums
  • Affected cats often change how they eat to avoid using a painful tooth, instead preferring soft food, or eating kibble without chewing
  • FORLs are often noticed during a routine wellness exam, with a more thorough diagnosis being made under anesthesia during a dental procedure
  • FORLs have no known origin or root cause, and there is no way to prevent the appearance of or progression of the lesions
  • Removal of the affected teeth is the most viable recourse, treating the symptoms and making the cat more comfortable
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A closer look: Feline Odontoclastic Resorption Lesions (FORLS) in Cats

It is common for FORLs to go unnoticed. Sometimes a cat with FORLs changes their eating habits. They may try to swallow dry food without chewing, or tilt their head in such a way as to avoid using an affected tooth. The cat may prefer eating wet food if the option is available.

In extreme cases where an eroding tooth causes pain, or if several teeth are affected, the cat may exhibit a reduced appetite.

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Risk factors

FORLs are very common in cats, and become more so as a cat grows older.

The condition is not an emergency, although an affected tooth is usually extremely painful when touched. Dental surgery is required to remove any affected teeth.

Possible causes

FORLs are idiopathic, meaning they have no known origin or root cause. Some theories suggest that vitamin D deficiency or progression of periodontal disease is responsible, however there is currently no consensus among the veterinary community.

Main symptoms

Early FORLs look like a tiny pink spot in the dental enamel. A tooth that is affected by FORLs gradually grows darker, with a reddish or brown color resembling dried blood expanding across the surface of the tooth, typically starting at the root of the tooth.

Over time the tooth appears to wear away, sometimes accompanied by inflammation of the gums. In the final stages, the tooth is completely resorbed, leaving only a bump beneath the gums in place of where the tooth was originally.

Testing and diagnosis

A physical examination is often sufficient to diagnose FORLs, however initial symptoms often appear below the gumline. Dental x-rays are required to determine how many teeth are affected.

Steps to Recovery

As there is no known treatment preventing or reducing FORLs, veterinary assistance relies on removing the affected teeth to reduce pain and discomfort for the cat.

If FORLs have progressed to a point where a tooth is completely resorbed but no other teeth are affected, no treatment is necessary.

When one FORL is noticed, dental X-rays often reveal multiple affected teeth. Recurrence of FORLs is common.


FORLs are not known to be contagious, and there are no known ways to prevent the condition.

Are Feline Odontoclastic Resorption Lesions (FORLS) in Cats common?

FORLs are very common in cats. Incidence rate estimates range from 20%-75% of cats being affected, with the percentage increasing with the cat’s age.

Typical Treatment

Removal of the affected teeth


Jan Bellows, DVM, DAVDC - Writing for Veterinary Partner
No Author - Writing for Cornell University College of Veterinary Medicine
Cecilia Gorrel, BSc, MA, Vet MB, DDS, MRCVS, Hon FAVD, DEVDC - Writing for Veterinary Partner

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