Cavities in dogs:what tooth decay looks like, why it matters and how it is treated

Do dogs get cavities, and why

Caries is the destruction of the hard tissues of a tooth by acid. Bacteria in dental plaque break down sugars and starch from food and release acids, which gradually dissolve the minerals first of the enamel and then of the dentine — the tissue underneath. The affected area softens and darkens, and over time a cavity forms in the tooth.

In dogs, caries is less common than in people. The reasons usually given include the shape of the teeth: most are pointed, with no deep hollows where plaque could sit. The composition of saliva and of the bacteria in the mouth also plays a part, as does diet, which usually contains less sugar than a human one.

But dogs also have teeth with a broad chewing surface — the molars, which they use to crunch and grind food. Plaque and food debris collect in their natural pits and grooves, so this is where decay most often appears. That is why I check the chewing surfaces of the molars specifically at every examination under anaesthesia.

Where cavities usually appear in dogs

In dogs, caries usually starts where plaque is left undisturbed for a long time — in the deep pits and fissures of the chewing teeth:

• Upper first molars (109 and 209) — the most typical site: the pits on their broad chewing surface.
• Lower molars — the hollows on the chewing surface that the upper teeth meet.
• Other teeth with deep natural grooves that are hard to clean with a brush.

The numbers 109 and 209 refer to the modified Triadan system that veterinary dentists use to identify teeth. Decay often affects the same tooth on both sides, so when I find it on one side, I check the matching tooth on the other side carefully.

What tooth decay looks like in dogs

Caries develops slowly, and owners usually notice it by chance — while brushing their dog's teeth or when the dog yawns. Things to watch for:

• A dark — brown or black — spot in a pit on the chewing surface of a large back tooth. “What is this black spot on my dog's tooth?” is one of the most common reasons owners get in touch.
• A hole in the tooth — a hollow with dark, soft contents where food can get stuck.
• Chalky grey enamel edges around the spot: the enamel has lost minerals, and the dentine beneath it is already destroyed.
• A broken-off piece of crown — when the enamel over the cavity collapses.
• Changes at mealtimes: the dog takes hard treats carefully, crunches food on one side only, drops food; bad breath appears.

The key sign of caries is texture: affected dentine is soft, almost leathery, and a sharp dental explorer sinks into it and slightly “sticks”. Healthy enamel, a worn surface or old staining feel hard and smooth. This is checked during the examination under anaesthesia.

Other reasons a tooth can look as if it has a “hole” are collected on the page Hole in a tooth.

Cavity or not: what it gets mistaken for

A dark spot on a dog's tooth is not yet a diagnosis. Several conditions can look similar, and most of them are treated differently:

• Staining and dental deposits. Brown plaque or tartar sits on the surface of the tooth, usually near the gum, and does not make the tooth soft. What each shade can mean is explained in the article Yellow, brown and black teeth in dogs.
• Wear. The tips of the teeth are flat, and in the centre of the worn surface there is a smooth, hard brown dot of tertiary dentine, which the tooth lays down to protect itself from slow wear. More on the page Worn teeth.
• A chip or fracture with exposed dentine. Sharp edges, a “step” in the tooth, hard yellowish dentine. A pink or dark dot in the centre of the fracture means the pulp is already exposed.
• Enamel defects. Rough chalky, yellow or brown patches, often on several teeth; they form while the tooth is developing and feel hard.
• A darkened tooth. If the whole tooth has turned pink, grey or purple, the colour has changed from the inside because of pulp damage. See the page Darkened tooth.
• Tooth resorption (TR). It also occurs in dogs: the defect is usually at the gum line and is filled in by gum tissue.

By eye, and even more so in photos, these conditions are easy to confuse. That is why caries is finally told apart from them during the examination under anaesthesia — with an explorer and on dental radiographs.

Why tooth decay in dogs matters

Caries does not stop or heal on its own. Dentine is softer than enamel, so once the lesion gets through the enamel it spreads faster downwards and sideways — under enamel that still looks intact. As a result, a small spot on the surface often hides a much larger cavity.

From there, things develop just as they do after a tooth fracture: bacteria reach the pulp, it becomes inflamed (pulpitis) and eventually dies, and the infection spreads through the root tips into the bone. With the upper molars, this inflammation sometimes shows as a swelling or a draining tract under the eye. How pulpitis develops and why it matters is explained in the article Pulpitis in a dog or cat.

A tooth with deep decay hurts even if the dog is eating as usual: animals adapt and crunch food on the other side. So the absence of complaints is no reason to wait.

1. 01

   Enamel

   A dark spot or a shallow pit. At this stage the lesion is usually small, and the tooth is repaired with a restoration.

2. 02

   Dentine

   The cavity deepens and spreads under the enamel. If the pulp is not involved, the tooth can still be restored with a filling.

3. 03

   Pulp

   The decay has reached the pulp: pulpitis, then pulp death. Root canal treatment is needed to save the tooth.

4. 04

   Bone at the root

   The infection spreads beyond the root tip: abscess, swelling, a draining tract. The tooth is treated endodontically or extracted.

How cavities in dogs are diagnosed

At the consultation I look at the teeth, gums and bite and may suspect caries from its appearance. But the depth of a lesion cannot be assessed in an awake dog: it requires touching the tooth with an explorer and taking radiographs, which is only possible under general anaesthesia. The anaesthesia is given and monitored by a separate veterinary anaesthesiologist.

Under anaesthesia, as part of COHAT, I:

• check every tooth with a sharp dental explorer — soft, “sticky” dentine distinguishes caries from staining and tertiary dentine;
• examine the matching teeth on the other side and the remaining chewing surfaces;
• carry out periodontal probing — the state of the gums and bone also affects the choice of treatment;
• take dental radiographs of all the teeth: they show how close the lesion has come to the pulp, whether there are changes at the root tips and whether other teeth have hidden lesions.

Early caries may not yet be visible on a radiograph, and radiographs can underestimate the depth of a lesion. Its full extent becomes clear when the softened tissue is removed during treatment, so I discuss the plan with you in advance, including the possible alternatives.

How cavities are treated: depending on depth

Caries is not treated with gels, pastes or antibiotics: the softened, infected tissue has to be removed mechanically. What happens next is decided on clinical indications — depending on how deep the lesion goes:

• Restoration (filling) if the pulp is not involved. I remove all the softened dentine, shape the cavity and fill it with restorative material, rebuilding the shape of the chewing surface; deep fissures next to it can be sealed if needed. How this works and how a restoration differs from a crown is covered in the article Tooth restoration (filling) in dogs and on the page on restorative dentistry.
• Root canal treatment if the decay has reached the pulp. The affected or dead pulp is removed, the canals are cleaned and filled, and the crown is rebuilt with a restoration. Molars have several roots, so this treatment is more complex than for a single-rooted tooth, and the result is checked on follow-up radiographs. More on the page on endodontics and root canal treatment.
• Extraction if the tooth cannot be saved. When the crown is so destroyed that it cannot be rebuilt, the lesion has reached the root, there is severe periodontal disease or root canal treatment is not possible, the tooth is extracted surgically — with the roots sectioned and a follow-up radiograph.

I explain all the options after the radiographs and agree the plan with you. Sometimes two routes are possible for the same tooth, and the choice depends on its role, the state of the other teeth and whether you can come back for follow-up checks.

How to lower the risk of cavities in dogs

Caries develops where plaque stays on the tooth for a long time and its bacteria get carbohydrates from food. So prevention comes down to a few things:

• Daily toothbrushing with a soft brush and veterinary toothpaste, so plaque has no time to build up in the pits of the molars. Human toothpaste is not used for dogs — the xylitol in some brands is toxic to them.
• No sugary or starchy human food. Biscuits, bread, sweets, desserts and “a bite from the table” give plaque bacteria exactly what they make acids from. Frequent snacks of this kind do the most harm.
• Fissure sealing when clinically indicated. If the chewing teeth have deep pits and grooves that a brush cannot clean, they can be closed during COHAT with a special flowable material — a sealant: the surface becomes smoother and holds less plaque. In the fissure sealing case in a dog, this was done for the natural grooves of the upper fourth premolars 108 and 208, where plaque built up quickly despite daily brushing.
• Regular check-ups. How often is something I advise individually — based on the state of the teeth, home care and whether caries has been found before. I check sealants and fillings at routine examinations.

Do cats get cavities?

True caries is not a typical finding in cats. If you see a “hole” at the gum line of a cat's tooth, a pink spot or red tissue that seems to grow onto the tooth, it is most likely tooth resorption (TR) — a process in which the tooth is destroyed by the body's own cells. Such a tooth is not filled, because resorption continues under the filling. Why, and how it is treated, is covered in the article Cavities in cats? Why it is usually tooth resorption.

Resorption also occurs in dogs, so a defect at the gum line in a dog should also be checked on radiographs rather than assumed to be a cavity.

What the cost of treating a cavity depends on

The first step is a consultation. Diagnosis and treatment are carried out under inhalation anaesthesia with dental radiography, as part of COHAT.

The cost of the treatment itself depends on how many teeth are affected, how deep the decay goes and which method is chosen — restoration, root canal treatment or extraction — so I give it after the diagnostics.

Frequently asked questions