Tooth resorption (TR) is a common feline condition during which your cat may lose the internal or the external part of the tooth. It is an affliction that affects cats, predominantly, though also some dogs, and can manifest as external or internal root resorption, feline odontoclastic resorptive lesions (FORLs), cervical line erosions, cavities, or neck lesions.

While tooth resorption can occur at any age, it’s most prevalent in older cats, with more than half of cats that are 3 years or older affected by resorption. You will probably be able to spot tooth resorptions after careful examination of your cat’s mouth. They will appear on the lower outside part of the tooth, where the tooth meets the gum. The molars on the lower jaw, in particular, are susceptible to tooth resorption, though it can occur on any healthy tooth.

What are the causes of tooth resorption?

While extremely common, tooth resorption is one of those afflictions where the cause remains unknown, even today. There are, however, theories as to why this happens. One popular theory suggests it might be some sort of autoimmune response, triggered as the feline gets older.

Other possible causes for tooth resorption in cats include a metabolic imbalance due to calcium regulation, or calicivirus (a highly infectious virus that leads to severe respiratory infection in cats).

The stages of tooth resorption

Tooth resorption will most commonly start out as a lesion along the gum line, and progress gradually, eroding denting (the sensitive part of the tooth beneath the enamel). In some cases, the diseased cat will exhibit jaw spasms as the disease progresses, excess salivation, bleeding, and may have a hard time eating, while others may experience pain. Touching the lesion is particularly painful.

In some more obvious cases, you may be able to spot the warning signs of tooth resorption yourself, while others might also be observed by a licensed vet.

Tooth resorption usually follows five different stages, recognized by most professionals. As with many diseases, the trouble with tooth resorption is that you’ll most likely notice there is something wrong only during the later stages of the disease.

During Stage 1, you will only see damage at the enamel level. Naturally, this is the most minimally bothersome stage. In Stage 1, you may notice lesions near the enamel, though keep in mind these won’t be overly sensitive, and your cat may not exhibit severe reactions to touch. This is because, during this initial stage, the disease has not yet affected the dentin.

That’s what happens in Stage 2, the lesion enters the dentin, breaking through the protective enamel layer. Your cat will begin to exhibit stronger reactions, as the pain worsens, since dentin is, after all, a lot more sensitive.

In Stage 3, resorption will have moved on to the pulp chamber of the tooth. That means it has started affecting the nerve itself, which causes serious pain and difficulty eating.

By Stage 4, severe damage has occurred. Large parts of the hard structure of the tooth have already been destroyed, and you will be able to observe the decay with the naked eye.

Stage 5 is the final stage, by which point, resorption has nearly completed, and most of the tooth is gone, leaving behind a gummy bump , instead.

If your vet suspects tooth resorption, they will require intraoral X-rays to evaluate the state of each tooth. Depending on these, they will prescribe a course of treatment that may involve the extraction of the tooth and root, or at least, a partial extraction. If the resorption has reached the final stage without major inflammation, treatment won’t be required.