Short answer: Dental probiotics add live microorganisms, and postbiotics add deliberately inactivated ones, to a pet's daily routine, with the aim of supporting a balanced oral environment. In dogs, a handful of specific strains and preparations have been studied in small, short-term controlled studies: grade B, for those exact strains only. In cats, one small study shows a shift in the oral microbial community, with no comparable plaque evidence. No probiotic replaces daily cleaning or veterinary care, and a responsible product claims no more than that it is designed to support a balanced oral environment.
The definitions that matter
Three words do most of the work, and all three are used loosely. We use the consensus definitions of the International Scientific Association for Probiotics and Prebiotics (ISAPP).
- Probiotic: live microorganisms that, when given in adequate amounts, confer a health benefit on the host. The benefit belongs to the strain, identified by genus, species and strain code, for example Enterococcus faecium NCIMB 10415.
- Prebiotic: a substrate, usually a fibre such as inulin, that is selectively used by microorganisms already living in the host and confers a health benefit.
- Postbiotic: a preparation of inanimate microorganisms and/or their components that confers a health benefit on the host (ISAPP, 2021). Heat can inactivate a strain, but inactivation alone does not make a postbiotic; the exact preparation needs its own evidence. Until it has that evidence, scientists call it a defined inactivated microbial preparation.
Notice what the three definitions share: a demonstrated benefit. On a label, “probiotic” often just means “contains live cultures”. The science asks a harder question: has this exact strain, or this exact preparation, shown a benefit in this species?
How they are proposed to work
Several mechanisms have been proposed. Most rest on laboratory work or reasoning rather than on measurements in pets' mouths, and we grade them accordingly.
| Proposed mechanism | The idea | Grade in dogs and cats |
|---|---|---|
| Competitive exclusion | Added microbes take up space and nutrients on the teeth and gums, leaving less room for others. | E to D |
| Biofilm modulation | A strain, or its components, changes how plaque biofilm builds up and how it is organised. | D, with early B signals for specific strains in dogs |
| Adhesion and coaggregation | Microbes or their cell components bind to other microbes, or to the film on the tooth, changing who sticks where. | D |
| Local chemistry | Some strains produce substances, or alter acidity, in ways that affect their neighbours. | D |
Two further points shape how any of this might work in practice. Postbiotics are not alive and cannot settle in the mouth, so any effect has to come from their cell components or the substances they carry. And live probiotic microbes appear to persist only briefly: a 2026 review of microbe-based approaches in dogs listed short persistence among the field's open challenges. Either way, any effect is likely to depend on regular use, and none of it replaces mechanical cleaning.
What has been studied in dogs
These are the dog studies we have graded. Each result belongs to the exact strain or preparation, the amount and the format tested.
| Study | What was tested | What the authors reported | Grade |
|---|---|---|---|
| Florit-Ruiz and colleagues, 2025 | A heat-treated Lactiplantibacillus plantarum CECT 9161 preparation at two daily amounts, against placebo, in 60 dogs | Associations with changes in plaque-related measures and in the genes of the oral microbial community | B for this preparation |
| Hu and colleagues, 2026 | Two live strains, Lactiplantibacillus plantarum Kmiate-6 and Pediococcus acidilactici Kmiate-15, for 21 days | Changes in plaque measures, in salivary markers and in the oral community, including a lower share of Fusobacterium and Porphyromonas; in laboratory tests the strains slowed the growth of oral microbes | B for this combination; D for the laboratory work |
| You and colleagues, 2022 | Lactobacillus acidophilus MJCD175, a strain isolated from dogs, given alone or in a multi-strain mix | The single strain was associated with less Porphyromonas gingivalis DNA in the mouth; the multi-strain mix did not show the same effect | B small study; D for the laboratory screening |
Read together, these studies are a genuine signal and a good reason for more research. They are also small, short and strain-specific, and some are linked to the organisations that developed the strains. Other published dog studies have tested commercial fermentation products whose exact strains are not clearly disclosed, which makes them impossible to reproduce or compare, so we do not grade them as strain evidence. None of these studies tested a Petdentist® product.
What has been studied in cats
The cat evidence is thinner, and we say so rather than borrow from dogs.
- A 2024 study in cats fed three strains, Bifidobacterium animalis subsp. lactis HN019, Lactobacillus acidophilus NCFM and Lactobacillus casei LC-11, for 42 days and found shifts in the microbial community at several sites in the mouth B for those strains, community measures only. The authors described the feline evidence base as underexplored. One of these strains has also been studied in people; we do not count that towards cats.
- A 2026 review brought together studies showing that the cat's oral microbial community shifts in common oral conditions C.
- Still missing: plaque evidence in cats comparable to the dog studies, and any evidence that effects last.
A changed community is not the same thing as a cleaner mouth. For the practical side, see dental probiotics for cats and dental probiotics for dogs.
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.
The limits, plainly
- Small samples. The largest dog study we have graded involved 60 dogs. Small studies can produce chance findings and imprecise estimates.
- Short duration. Weeks, not years. Whether any effect lasts, or fades when use stops, is unknown.
- Strain-specific. A result belongs to one strain or preparation, at one amount, in one format. It does not transfer to a different strain of the same species, let alone to a different product.
- Laboratory measures. A shift in microbial DNA may or may not mean a difference you, or your vet, would notice.
- Who ran the study. Early studies often come from the organisations developing the strains, which is why independent replication matters.
- More is not automatically better. In one dog study, a multi-strain mix did not show the effect seen with a single strain.
How to read a study
- Which species? Dogs, cats, people or a laboratory dish? Only studies in the same species count, and only for that species.
- Which exact strain or preparation? Genus, species and strain code, and whether it was live or inactivated.
- How much, in what, for how long? The daily amount, the format (powder, chew, gel) and the duration.
- Compared with what? A placebo or control group, ideally with the person scoring the teeth unaware of who received what.
- What was measured? Plaque scores, microbial DNA or breath compounds, and whether that is what matters to you.
- How many animals? Small studies are a start, not an answer.
- Who ran and funded it, and has anyone repeated it?
- Does the product in front of you match? The same strain or preparation, at the same amount, in the same format. If not, the study is about something else.
What a responsible claim looks like
Evidence decides what can be said about a probiotic, and the law narrows it further: in the UK, a non-medicinal product may only be presented as maintaining health in healthy animals, whatever evidence it holds.
| Wording | Our view | Why |
|---|---|---|
| “Designed to support a balanced oral environment” | Responsible | Describes the intended role, in maintenance terms, for healthy pets. |
| “Contains [named strain] at [stated amount]” | Responsible, if true | A factual statement of composition that can be checked against the label and the batch. |
| “Part of a daily routine, alongside brushing and veterinary care” | Responsible | Places the product where the evidence puts it. |
| Any plaque-reduction wording | Not without that product's own trial | Plaque claims need a controlled trial of the exact product, in the species it is sold for. |
| Any disease named beside the product | Never | It would present a complementary feed as a medicine. |
| Wiping out germs, or resetting the microbiome | Never | Neither the aim of oral hygiene nor permitted for a non-medicinal product. |
We apply the same test to ourselves. Petdentist® Probiotics Powder for Cats & Dogs is a complementary feed, served over food by body weight as the pack directs and designed to support a balanced oral environment as one part of the daily routine. None of the studies on this page tested it, and we do not borrow their results.
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.