Tooth resorption in cats: when teeth dissolve from within

She eats. She purrs. She lets you stroke her. And yet a tooth in her mouth may be falling apart right now — not from decay, but because her own body is breaking it down, from the root upwards, layer by layer. This dental disease is called tooth resorption, or FORL for short. It is one of the most common conditions in adult cats, and the one most reliably missed — not because people are careless, but because cats are built so that you see nothing.

Tooth resorption — in full, feline odontoclastic resorptive lesions, often shortened to FORL — is a clumsy term for a simple, unsettling process: the tooth is dissolved by the cat's own cells. When I tell people their cat has probably had toothache for months, the same sentence comes back almost every time: “But she eats perfectly normally.” That is exactly the point. With tooth resorption, eating well is not an all-clear. It is the camouflage.

What is actually happening

Four words, four letters — and not one of them means anything on first reading. So, one at a time:

• F for feline — relating to cats.
• O for odontoclastic — caused by odontoclasts, the cells that break down tooth substance. From the Greek odous, tooth, and klastes, breaker.
• R for resorptive — dissolving. The body takes back what it built itself.
• L for lesions — damage. The craters and holes left behind.

Put together, FORL means: damage to a cat's teeth, caused by the cat's own cells dissolving the tooth.

These cells work from the inside, starting at the root — often exactly where the tooth meets the gum.

So it is not decay. No bacterium is eating a hole. The body is dismantling its own tooth, layer by layer, until the nerve fibres lie exposed. And then every bite hurts, every mouthful of cold water, every touch.

How common it is depends on which study you read and how old the cats were — figures range from around one in five to more than one in two adult cats. That is a wide spread, but every survey points the same way: it is common, and it becomes more common with age.

Why your cat tells you nothing

This is the heart of it, and it has nothing to do with teeth.

A cat is both hunter and prey. An animal that visibly weakens gets eaten — that calculation sits deep in her, even after twelve years on a sofa where the only enemy is the vacuum cleaner. Showing weakness is not an option for a cat, it is a risk. So she shows none.

Then comes the second part: not eating is not an option either. A prey animal that skips a meal because it is unpleasant does not survive a bad week. So she eats. Through the pain, on the side that hurts less, if necessary by swallowing the pieces whole.

What looks to us like “she is fine” is in truth a very old, very effective ability to show nothing. Anyone waiting for a cat to report pain waits forever.

The signs nobody connects with teeth

There is something to see — just rarely where people look. These are the observations people describe to me without realising they are describing a mouth:

• She swallows dry food whole. Chewing hurts, swallowing does not.
• She drops pieces again or shakes her head briefly while eating.
• She chews on one side only, or suddenly prefers wet food.
• She grooms less — and the coat turns dull or mats along the back. Grooming needs teeth.
• She no longer wants to be stroked on the head, or gets sharp about it.
• She drools, sometimes only a damp patch where she sleeps.
• She withdraws, is more irritable, seeks less contact.
• She stops using the litter tray properly — lasting pain changes behaviour, including there.

Notice how many of those sound like “personality”? Or like “she is just getting older”? That is where detection usually fails. Not at looking, but at interpreting. If your cat is also eating less, read what I have written about cats that stop eating — there too, the most commonly missed cause sits in the mouth.

Tartar is not the cause — and brushing is not prevention

This is the point where I most often have to contradict someone, and I usually disappoint a person who was trying to do everything right.

Tooth resorption is not caused by poor dental care. There are cats with spotless teeth and severe lesions, and cats with a decent layer of tartar and not a single one. Why the body starts dismantling its own tooth is still unexplained. There are theories — vitamin D metabolism, diet, genetic predisposition — but none of them is proven.

Brushing is still worth doing: against tartar, against gum inflammation. Just not against this. Anyone promising otherwise is selling you something.

What genuinely helps is unspectacular: pay attention, and have the mouth looked at properly once a year. From about five years of age, this belongs in every check-up.

Why only an X-ray gives certainty

Some lesions sit below the gum. From outside there is nothing to see — no hole, no discolouration, sometimes only a tiny red spot at the gum margin that gets taken for irritation. A tooth can look flawless above and already be half dissolved below.

That is why dental radiographs are needed, and in a cat that only works under anaesthesia. I know that is the sentence where many people flinch. The alternative, though, is to let the animal go on living with a pain it cannot show — and I weigh that pain considerably heavier than a well-prepared anaesthetic in a healthy cat.

A visible hole in the tooth, by the way, is not an early sign. It is a late one.

The treatment sounds drastic and is a release

A tooth being resorbed cannot be repaired. No filling, no crown, no root canal stops it — the breakdown continues. The only treatment that truly ends the pain is removing the affected tooth. Which form of removal is right in a given case depends on the X-ray and is decided by the vet holding that image.

And then something happens that moves me every time: people ring after two or three weeks and say their cat is “like a different animal”. She plays again. She comes onto laps again. She grooms again. None of that had registered as illness before — it had only become a little less, over months, imperceptibly.

The most common worry: how will she eat without teeth? Remarkably well. Cats barely chew their food anyway, they break it up. Even cats that lose all their molars usually go on eating normally afterwards, dry food included. A pain-free mouth without teeth beats a painful one with.

What lasting pain does to the rest of the cat

For me the matter does not end at the tooth. Pain lasting months does not stay in the mouth. It holds the nervous system in permanent alert, and a body on alert recovers less well, digests less well, sleeps less well.

That is why I so often see something else in cats with advanced lesions: a dull coat, a sensitive stomach, withdrawal, sometimes aggression nobody can place. Those are not coincidences on the side. That is an animal that has spent a year in a state of emergency while acting as if nothing were wrong.

If you wonder how conventional medicine and the holistic view fit together: here the division of labour is very clear. The tooth needs X-raying and treating, that is craftsmanship and not negotiable. What comes afterwards — how a body finds its way out of prolonged stress, what the animal needs in support, how behaviour settles again — is where the wider view earns its place. More on that in Holistic veterinary medicine: when it makes sense.

What I would like you to take away

Do not measure your cat's condition by whether she eats and purrs. She can do both in considerable pain. Measure it by change: what does she do less of than a year ago? Does she still groom as thoroughly? Does she still come as often? Does she still chew on both sides?

A cat that shows you nothing is not healthy. She is a cat.