Cat dental disease: what the smell test misses

Quick answer

Cat mouth examination in progress

Bad breath is a late sign, not a test. By the time a cat's mouth smells, there is usually established periodontal disease with anaerobic bacteria under the gum line.

The conditions that hurt cats most, tooth resorption in particular, frequently produce no odour at all, and a cat with a mouth full of pain will keep eating because not eating is worse.

• Judge the mouth by looking at it, not by smelling it, and look at the gum line rather than the tooth tips.
• Chewing on one side, dropping food, swallowing kibble whole and jaw chattering are pain signs.
• A normal appetite tells you nothing about dental pain in a cat.
• Around half of feline dental disease sits below the gum line and can only be seen on radiographs taken under anaesthesia.
• Brushing prevents periodontal disease. It does not prevent tooth resorption, which has a different cause.

Decide in 60 seconds

Why breath is a poor test

Odour in a cat's mouth comes mainly from volatile sulphur compounds produced by anaerobic bacteria living in the space between gum and tooth. Those bacteria thrive once a pocket exists, which is a mid to late stage of periodontal disease.

Two things follow.

Disease without smell. A resorptive lesion at the gum line of a premolar, a fractured canine with an exposed pulp, or early gingivitis can all be present with breath that seems normal to an owner sitting a metre away.

Smell without dental disease. Kidney disease produces an ammoniacal or urine-like odour on the breath. Diabetic ketoacidosis produces a sweet, acetone smell. Oral ulceration from calicivirus, a string or grass blade caught around the tongue base, and even a chronically infected lip fold all cause odour.

So the smell test fails in both directions. Looking is better, and looking at the right place matters more than looking at all.

The four diseases that matter in cats

Periodontal disease.

Plaque forms as a bacterial biofilm within a day of a clean surface. Left in place it mineralises into calculus, which is rough and holds more plaque. The damage is not done by the calculus itself, but by the immune response to the bacteria, which destroys the ligament and bone that hold the tooth.

The visible sequence is a thin red line along the gum margin, then swelling and bleeding, then gum recession, then loose teeth.

Tooth resorption.

The single most under-recognised cause of feline oral pain. Cells called odontoclasts destroy the tooth from within, most often at the neck of the tooth where crown meets root, and most often on premolars and molars.

What you see is a pink or red defect at the gum line, sometimes with gum tissue growing into the hole. What the cat feels, if that area is touched, is enough pain to produce a jaw chatter or a sharp flinch even under sedation.

The cause is not known, so brushing does not prevent it. Radiographs are needed to classify each affected tooth, because the appropriate treatment differs depending on whether the root is still distinct from surrounding bone.

Chronic gingivostomatitis.

An intense inflammation extending well beyond the gum margins, often into the tissue at the back of the mouth where the jaws meet. The mucosa looks angry, raised and ulcerated.

These cats drool, refuse dry food, cry or scream while eating, paw at the mouth, stop grooming and lose weight. It is a disproportionate immune response rather than simply severe tartar, and treatment is often extraction of most or all of the teeth, after which a large proportion of cats improve markedly.

Fractured teeth and oral masses.

Cats fracture canines in falls and fights. If the pulp is exposed, bacteria track to the root tip and produce an abscess, which can appear as a swelling under the eye.

Oral tumours, most commonly squamous cell carcinoma, are the other reason not to assume dental disease. They present as a mass, a loose tooth in an otherwise reasonable mouth, facial asymmetry, or bloody drool. Early biopsy matters because these tumours are locally aggressive.

How cats show oral pain

The key point is that they keep eating. A cat that stops eating stops for a different or an additional reason, and by then the disease is advanced.

Cat with dental care items

Look for changes in how, not whether.

Chewing on one side of the mouth, or tilting the head while chewing.

Picking up kibble, dropping it, and starting again.

Swallowing dry food whole, then vomiting it back undigested.

A new preference for wet food, or for gravy licked off and the chunks left.

Approaching the bowl, hesitating, and walking away, then returning repeatedly.

Growling or crying at the food bowl.

Jaw chattering, a rapid tremor of the lower jaw, which in cats is strongly associated with resorptive lesions.

Reduced grooming, leading to a scruffy coat and mats over the back, because grooming uses the mouth.

Pawing at the face, or rubbing one side of the face on furniture.

Sleeping more, hiding, and becoming intolerant of being stroked around the head.

The retrospective test. Owners very often report that after dental treatment the cat became livelier, more affectionate and started grooming again. That change is the evidence that the previous state was pain, and it is why "he seemed fine" should not be reassuring.

The weekly home check

Thirty seconds, no restraint, at a time when the cat is relaxed.

Sit beside the cat rather than over it. Rest one hand under the chin, lift the upper lip on one side with a thumb, and look at the gum line where the gum meets the tooth. Then the other side. Then, if the cat allows it, gently tip the head back and look at the canines.

You are looking for:

A red or dark pink line where gum meets tooth, rather than an even pale pink.

Swollen gum margins, or gum that bleeds from a light touch.

A pink or red spot at the base of a tooth, especially on the cheek teeth, which suggests resorption.

Gum that has receded, exposing more tooth than on the other side.

A broken tooth, a missing tooth, or a tooth at a different angle from its neighbour.

Any lump, ulcer or asymmetry.

Brown or tan calculus, which is worth noting but is the least informative of these findings.

What the home check cannot do. It cannot see below the gum line, and that is where roughly half the pathology lives. A cat with an unremarkable home check can still have root resorption, bone loss or a retained root fragment.

Treat the check as a way to catch the obvious early, not as a substitute for an oral examination by a vet.

What changes by age and breed

Cat's mouth being examined

What actually prevents disease

Brushing is the only method that removes plaque.

Daily is what makes the difference, because plaque re-forms within a day. Use a cat-specific paste. Never use human toothpaste: it is not intended to be swallowed, and some human products contain xylitol, which should not be given to pets.

Introduce it over weeks, not in one session. Start with a finger and a taste of the paste, then a finger along the outer surface of the canines, then a soft brush or finger brush, and always stop before the cat objects. The outer surfaces of the upper teeth are what matter most, and the inner surfaces can be ignored.

A cat that has been handled around the mouth since kittenhood tolerates this easily. A cat introduced to it at eight years old may never accept it, and forcing the issue damages the relationship without improving the mouth.

Products with evidence.

Some dental diets and chews are formulated to reduce plaque or tartar, either mechanically through a fibre structure that scrapes the tooth rather than shattering, or chemically. An independent body, the Veterinary Oral Health Council, awards a seal to products that have met a defined standard, and looking for that seal is a more reliable filter than marketing claims.

Water additives and most treats sold as dental are weak by comparison. They are not harmful, but they should not replace an examination.

And the honest limit.

Brushing lowers the risk of periodontal disease substantially. It does not prevent tooth resorption, and it does not prevent gingivostomatitis. A cat with an immaculate home routine can still need extractions, and that is not a failure of care.

What happens at a proper dental appointment

A conscious examination in the consulting room shows the outer surfaces of some teeth in a cooperative cat. It cannot examine the inner surfaces, the back of the mouth, or under the gum, and no cat allows periodontal probing while awake.

A full assessment therefore happens under general anaesthesia and includes:

Pre-anaesthetic examination and blood tests, particularly in older cats, to check kidney and liver function.

Charting of every tooth with a probe, measuring pocket depth and recording mobility, recession and lesions.

Full-mouth radiographs, which routinely reveal resorption, root abscesses, retained roots and bone loss that were invisible on the surface.

Scaling above and below the gum line, then polishing.

Extractions where indicated, with local anaesthetic blocks and pain relief.

On anaesthetic risk in older cats. It is a legitimate concern and it is managed with pre-anaesthetic testing, intravenous fluids, monitoring and modern protocols. What is not risk-free is the alternative: chronic oral pain, difficulty eating, and a persistent source of infection.

What never to do

Do not use human toothpaste, bicarbonate paste or salt on a cat's teeth.

Cat being petted indoors

Do not attempt to scrape tartar off with a fingernail or a dental scaler at home. You will damage the enamel surface, leave a rougher tooth that accumulates plaque faster, and cause pain.

Do not book an anaesthesia-free cleaning in the belief that it treats disease.

Do not give bones or antlers as a dental measure. Cats fracture teeth on hard objects, and a fractured tooth with an exposed pulp is a worse problem than the tartar you were trying to remove.

Do not assume a cat that is eating is comfortable.

Do not delay investigation of a loose tooth in an otherwise sound mouth, or of a swelling on the gum. Both can be tumours.

Do not stop pain relief early after extractions because the cat seems fine. Cats mask discomfort during recovery too.

When to get help

Same day, for a cat that has stopped eating, is drooling heavily, or has a swollen face.

This week, for jaw chattering, blood in the water bowl, a changed chewing pattern, a red gum margin, a broken tooth, or a lump anywhere in the mouth.

At the next routine appointment, for tartar without other signs, and ask specifically whether the cat needs a full examination under anaesthesia with radiographs rather than a visual estimate.

Ask what will be done if painful lesions are found while the cat is under anaesthesia, and agree it in advance. It saves a second anaesthetic, which is better for the cat and cheaper for you.