Short answer: Plaque is a soft, sticky film of bacteria (a biofilm) that forms on teeth every day. In a dog's alkaline mouth, with saliva at around pH 7.5 to 8.5, minerals begin to harden plaque into tartar, also called calculus, within about 48 to 72 hours; cats' saliva is alkaline too. Soft plaque can be brushed or wiped away. Tartar cannot, and needs a veterinary scale and polish under anaesthesia. Daily cleaning along the gumline helps reduce plaque build-up and helps keep tartar from building up.
What plaque is
Plaque is not leftover food. It is a biofilm: a living, organised community of bacteria that fixes itself to the tooth and surrounds itself with a sticky matrix of its own making. It forms on every tooth, every day, and it is thickest where tooth meets gum.
Because the community is stuck to the tooth and shielded by its matrix, water, licking and ordinary eating will not shift it. It has to be physically disturbed, by bristles or a textured wipe, to come away.
That is why dry food alone does not clean teeth: kibble is crunched at the tips of the teeth and barely reaches the gumline, where plaque matters most.
How plaque turns into tartar
Human saliva is slightly acidic to neutral, at around pH 6.5 to 7.0. A dog's sits at around pH 7.5 to 8.5, and a cat's is alkaline too. Alkaline saliva is one reason dogs and cats rarely get the cavities people do, but it has a cost: calcium and phosphate come out of saliva readily and crystallise inside soft plaque.
Within about 48 to 72 hours, that mineral begins to set. The result is tartar, also called calculus: a hard, yellow-to-brown deposit bonded to the tooth. It is often most obvious on the outer surfaces of the upper cheek teeth and the canines, but it forms wherever plaque is left alone.
Tartar is rough and porous, so fresh plaque settles on it more easily than on smooth enamel, and each new layer can mineralise in turn. That is how tartar thickens over months and creeps under the gumline.
The plaque cycle, step by step
Timings vary between animals; the sequence does not.
Clean surface
Straight after cleaning, a thin film of saliva proteins, the pellicle, coats the tooth. Harmless on its own, it is what bacteria hold on to.
Soft plaque
Within hours, bacteria settle, multiply and wrap themselves in a sticky matrix. Young plaque is thin and easy to brush or wipe away.
Mature plaque
Over a day or two it thickens and spreads along the gumline, where oxygen is low and the bacterial mix shifts. Still soft; still removable.
Mineralising
From about 48 to 72 hours, minerals from alkaline saliva start to crystallise inside the plaque. It begins to set.
Tartar
Hardened plaque is bonded to the tooth, and fresh plaque builds on its rough surface. No brush can lift it.
Every time you clean, the surfaces you reach go back to step one. Leave them for two or three days and some plaque reaches step four. Once it is at step five, only your vet can reset it.
Why tartar cannot be brushed away
Tartar is mineral, bonded to the tooth. Bristles slide over it. Brushing harder does not help and can do harm: dog enamel is only about 0.1 to 0.6 mm thick, a cat's is a fraction of a millimetre, and gums bruise easily.
Scraping at tartar at home is a bad idea for the same reasons. Anything hard enough to crack tartar can scratch enamel and injure the gum, and it leaves the most important part untouched: the deposits and pockets below the gumline. A clean-looking crown can sit above an unhealthy root.
Be wary of any product that promises to dissolve or remove existing tartar on its own. Nothing served in a bowl, sprayed or chewed replaces professional removal.
What needs a professional scale and polish
The tartar you can see is not the main concern. What matters is what plaque does below the gumline, where it can gradually damage the tissues that hold a tooth in place. Vets call this periodontal disease, and assessing it properly needs an anaesthetic.
A veterinary dental clean is carried out under general anaesthesia, with the airway protected and the anaesthetic monitored throughout. That allows your vet to:
- examine every surface of every tooth;
- measure the gap between gum and tooth with a probe;
- take dental X-rays to see the roots and the bone around them;
- remove tartar above and below the gumline; and
- polish the teeth smooth, so fresh plaque has less to cling to.
Why anaesthesia-free "cleaning" is discouraged
Some services offer to scale pets' teeth while they are awake. The American Animal Hospital Association's 2019 dental care guidelines describe this as "not appropriate" for dogs and cats. An awake animal cannot be cleaned below the gumline, X-rayed or probed; the experience is stressful; and there is a risk of debris being inhaled. The guidelines also warn that it can give owners a "false sense of benefit": the crowns look white while whatever is happening underneath carries on.
When to see your vet
If you notice loose or wobbly teeth, swelling, discharge, bleeding that does not settle, reluctance to eat, dropping food, drooling, pawing at the mouth or any change in behaviour, please contact your veterinary surgeon promptly. Home care supports professional care — it never replaces it.
What home care can do
Home care cannot undo tartar, but it works with the clock rather than against it. As part of a daily routine, alongside veterinary care:
- Daily cleaning along the gumline, with a soft brush or a textured wipe, helps reduce plaque build-up.
- Cleaning at least every other day, inside the 48 to 72 hour window, helps keep tartar from building up. It counts most straight after a professional clean, when every surface starts smooth.
- Some daily dental powders, served over food by body weight, are designed to help soften existing tartar so it is easier to remove during normal care. Easier to remove means with brushing and at your next veterinary clean; it does not mean tartar disappears on its own.
What it cannot do is remove hardened tartar or reach below the gumline. That is your vet's job, which is why the best routine is home care and professional care together.
Home-care methods compared
Each method has a job. None of them does everything, and none of them replaces your vet.
| Method | What it does | What it cannot do | Good to know |
|---|---|---|---|
| Brushing with a soft brush and pet toothpaste | Physically disturbs plaque at the gumline. Helps reduce plaque build-up and helps keep tartar from building up. | Remove tartar, or reach below the gumline. | The core of home care. Learn it step by step: dogs · cats. |
| Textured wipe or finger brush | Cleans along the gumline on the outer surfaces, where plaque matters most. | Reach as far back as a handled brush, or remove tartar. | The best start for reluctant pets, and a real result if a brush is never accepted. |
| Dental powder served over food | Supports normal oral hygiene and helps reduce plaque build-up between cleans. Some are designed to help soften existing tartar so it is easier to remove during normal care. | Disturb plaque at the gumline, or stand in for cleaning. | Serving by body weight: follow the pack, building up from a quarter serving. Ask your vet before using kelp if your pet has a thyroid condition. Cats need a cat-labelled product. Powders |
| Water additive | Freshens breath through the day and supports normal oral hygiene. | Remove plaque or tartar. | Choose tasteless and odourless, add to fresh water daily, and go back to plain water if drinking drops. Water additives |
| Chews and toys | Add a little mechanical cleaning, mostly on the chewing surfaces. | Reach the gumline well, or stand in for cleaning. | Fingernail test: if you cannot dent it, it is too hard. Supervise. No hard chews for cats. Toys |
How strong is the evidence?
Here is how the key statements on this page are graded.
| Statement | Grade | What it means |
|---|---|---|
| Plaque begins to mineralise into tartar within about 48 to 72 hours in the alkaline mouths of dogs and cats. | C | Well-described oral biology in both species; the timing varies between animals. |
| Hardened tartar cannot be removed by brushing. | C | A physical property of mineralised calculus, and the reason professional removal exists. |
| A particular product helps reduce plaque build-up in a particular species. | A only if tested | Needs controlled trials of that exact product, in that species. The Veterinary Oral Health Council (VOHC) seal, for example, requires two independent clinical trials. |
| Results in dogs apply to cats. | Not transferable | Different mouths and a different metabolism. We grade cat evidence separately. |
The toothpaste we distribute, Petsmile® Professional Pet Toothpaste, has held VOHC acceptance for plaque in dogs since 2011. That acceptance belongs to that product, in dogs; it does not transfer to any other product or species. What the seal on the tube really means.
How we grade evidence
Every scientific statement on this site carries a grade: A product-specific controlled trial · B strain- or species-specific study in dogs or cats · C species mechanistic evidence · D laboratory (in-vitro) evidence · E theoretical rationale. The strength of a claim never exceeds the strength of its evidence. Read our evidence standards.