Tooth resorption in cats (TR)signs, stages, types and treatment

What tooth resorption (TR) is

Tooth resorption (TR) is a process in which odontoclasts — the body's own cells — gradually destroy the hard tissues of a tooth: cementum, dentine and enamel. Normally, similar cells dissolve the roots of a kitten's temporary teeth; in TR they destroy the permanent teeth of an adult cat.

The lesion usually starts on the outside — on the root surface near the gum line, where the enamel of the crown meets the cementum of the root. From there it spreads inwards, towards the pulp, and along the root. Gum tissue often fills the defect, so instead of a “hole” you see a red spot on the tooth.

The cause of TR is not fully understood, and there is no reliable way to prevent it. In adult cats it is a very common finding, it is found more often with age, and several teeth are frequently affected. TR is not limited to cats — it is also described in dogs.

Resorption is not a cavity: caries is caused by acids from plaque bacteria, whereas TR is caused by the body's own cells. More in the article cavities in cats: why a “hole” in a tooth is usually resorption. Older sources described the condition as feline odontoclastic resorptive lesions; today the term used is tooth resorption, or TR.

Enamel, gums and the tooth’s own tissues form a protective barrier, and resorption destroys it from within. I explain how this barrier works in How a dog’s and cat’s mouth works.

What tooth resorption looks like in cats and which signs you may notice at home

What you may see if you gently lift your cat's lip:

• a red spot or “bump” at the gum line — the gum seems to be growing into the tooth;
• a hollow or “hole” where the tooth meets the gum;
• part of the crown is missing, and the tooth looks chipped;
• the tooth seems to have vanished — there is only gum or a “stump” in its place (more in the article why is my cat losing teeth).

When the affected tooth is touched, the cat's jaw may chatter or tremble, or the cat may jerk its head away. While eating it may chew on one side only, drop food from its mouth, drool, prefer soft food and refuse dry food. Sometimes the only thing you notice is bad breath.

But many cats show no obvious signs, and resorption is found at an examination or on dental X-rays. Why appetite does not prove there is no pain is explained in the article why pets keep eating even with diseased teeth; other signs are covered in signs of tooth pain in cats.

1. 1The gum line. Pink with an even edge. A red line along the teeth, swelling or blood is a reason for a check-up.
2. 2Plaque and tartar at the gum line. Yellow-brown deposits collect most on the big upper cheek teeth.
3. 3Canine tips. Chips, cracks, a pink or dark dot where a tooth has broken.
4. 4A red “bump” at the gum line. The gum seems to creep over the tooth, or a red dot shows at the tooth’s neck — this can be tooth resorption (TR).
5. 5Incisors. Are they all there, and are any loose?
6. 6Back of the mouth, cheeks, tongue. Redness near the last teeth and at the corners of the mouth, ulcers, growths.
7. 7Face and jaws. Swelling under the eye or on the chin, asymmetry, pain on touch.

Stages of resorption: from a defect at the gum line to a “vanished” tooth

The stage is defined by how deep the lesion goes. Under the classification of the American Veterinary Dental College (AVDC) there are five stages:

• Stage 1 — mild hard-tissue loss: cementum, or cementum and enamel.
• Stage 2 — the lesion extends into the dentine but does not reach the pulp.
• Stage 3 — the lesion reaches the pulp; most of the tooth is still intact.
• Stage 4 — a large part of the tooth is destroyed, and the crown may break off.
• Stage 5 — the crown is gone, the gum has closed over the site, and root remnants show only on an X-ray.

Appearances are deceptive: a defect that looks small in the mouth may turn out to be deep on an X-ray, and roots may remain under the gum where a tooth seems to have “vanished”.

Types of resorption: why the type decides the treatment

The type of resorption is determined on a dental X-ray, based on what is happening to the root. It is the type, not how the tooth looks, that decides which treatment is possible.

• Type 1 — the root keeps its outline and root canal; there is often inflammation around the tooth.
• Type 2 — the root is gradually replaced by bone-like tissue and seems to merge with the bone.
• Type 3 — both types in one tooth, for example in different roots.

Put simply: a “true” root (type 1) must not be left behind — it will keep the pain and inflammation going, so it is removed completely. A root that the body is already turning into bone-like tissue (type 2) may, under certain conditions, be left in place. In type 3, roots with type 1 features are extracted, while a type 2 root can sometimes be left in place under the same strict conditions. Without an X-ray these situations cannot be told apart.

How tooth resorption is diagnosed

TR can be suspected at the in-clinic consultation, and if needed I prescribe pain relief straight away. But it is impossible to examine every tooth in a painful mouth without anaesthesia.

Under anaesthesia I check every tooth with a dental explorer, a fine probe: a resorptive defect feels rough, the probe “catches” in it, and touching it sometimes triggers a reflex jaw tremor.

An essential step is full-mouth dental radiography. Some lesions develop on the root below the gum and cannot be seen without X-rays. Dental X-rays show the stage, the type and the condition of the roots and bone, as well as other affected teeth that look healthy in the mouth. More in the article why do pets need dental X-rays.

Anaesthesia is inhalational, with continuous monitoring. Before it, a complete blood count and blood biochemistry are needed; echocardiography, abdominal ultrasound and other tests are added depending on the cat's age and health. On the risks, see general anaesthesia for dogs and cats: is it safe?.

Treating resorption: extraction or crown amputation

A tooth affected by resorption cannot be restored — the process is irreversible. The aim of treatment is to remove pain and inflammation. The approach is chosen for each tooth separately, based on the stage and type of resorption.

• Extraction of the tooth with its roots — the main treatment. In type 1 the roots are removed completely, and a follow-up X-ray confirms that no fragments are left.
• Crown amputation — the crown is removed, and the root, which is being replaced by bone-like tissue, is intentionally left in place. This is possible only in type 2, when the X-ray shows no root canal or periodontal ligament space, there is no periodontitis or endodontic (periapical) disease, and the cat has no stomatitis — with follow-up X-rays afterwards.
• Monitoring — if the changes are visible only on an X-ray and the defect has not opened into the mouth, monitoring with repeat X-rays may be possible in selected cases.

Fillings do not work: the cells keep destroying the tooth underneath and around the filling, it falls out and the pain comes back. That is why restoration is not recommended for TR.

I prescribe pain relief individually — give it only as prescribed. Once healed, cats usually eat well, even when many teeth have been extracted. More in the articles when does a cat need a tooth extracted and life for a cat without teeth, and on the tooth extraction page.

Home care and monitoring: can resorption be prevented?

Brushing alone will not prevent resorption. Brushing with a veterinary toothpaste reduces plaque and is good for the gums — see how to brush a cat's teeth — but it does not remove the cause of TR.

So what matters most is regular check-ups. If resorption has already been found, other teeth may become affected over time, so I set the interval for check-ups and repeat dental X-rays individually.

After extractions, the cat eats soft food for a few days, gets pain relief as prescribed and returns to its usual diet after the follow-up visit. Step by step — in the article aftercare following tooth extraction.

Between visits, watch for these signs:

• red spots or “bumps” on the teeth at the gum line;
• jaw chattering or jerking the head away while eating;
• chewing on one side, dropping food, drooling.

Myths about tooth resorption in cats

What I often hear from owners — and what I tell them:

• “It's a cavity, it can be filled.” No: resorption is caused by the body's own cells, and it carries on under a filling.
• “If the cat is eating, nothing hurts.” Cats hide pain and adapt: they chew on one side and swallow food without chewing. Appetite is no proof of healthy teeth.
• “Resorption is visible straight away.” Early lesions, and those that start on the root, are often invisible in the mouth — open defects are found with a probe, and those under the gum only on dental X-rays.
• “Extracting teeth will make the cat's life worse.” A tooth with open resorption hurts, and it cannot be saved anyway. Once healed, cats usually eat well — see life for a cat without teeth.
• “We can wait until the tooth falls out by itself.” While the crown is breaking down, the tooth hurts, and when it breaks off, roots may remain in the bone — in type 1 they keep the inflammation going.
• “Only old cats get it.” Resorption is found more often with age, but it also occurs in young adult cats.

How much diagnosis and treatment of resorption cost

The cost is made up of the consultation, pre-anaesthetic tests, anaesthesia and the COHAT procedure: examination, probing, full-mouth dental X-rays and professional cleaning.

Frequently asked questions