Oral probiotics for gums and breath: what the trials show, and what I told patients

Somewhere around 2015 a patient asked me whether she should be "taking a probiotic for her teeth," and I did not have a good answer, so I went and read. I kept reading for the next eight years, as the question came up more and more often, and this article is what I ended up telling people once I had a view. It is a qualified view. I am going to try to give you the qualifications as carefully as the view.

The idea, in one paragraph

Your mouth has a resident population of bacteria, hundreds of species, living in the plaque on your teeth, the coating on your tongue, and the grooves between your gums and teeth. Some of those species produce the acids that cause decay, the toxins that inflame gums, and the sulfur compounds that smell. Others do not, and some of the others actively make life harder for the troublemakers by competing for food and space and by producing their own antibacterial compounds. An oral probiotic is a dose of the second kind, delivered as a lozenge or chewable tablet that dissolves slowly so the bacteria have time to settle in rather than being swallowed. The hope is that over weeks of daily doses, the balance shifts.

That is the idea. Whether it works is a question about specific strains, specific doses, and specific outcomes, and that is where the reading starts.

What the trials measure

Gum trials usually report three things. The gingival index, which is a score for redness and swelling. The plaque index, which is how much plaque is visible after staining. And bleeding on probing, the percentage of sites that bleed when the hygienist runs the probe along the gum. Breath trials measure volatile sulfur compounds with a handheld meter, or use a panel of trained sniffers, which is as awkward as it sounds.

The strain with the most and best trials for gums is Lactobacillus reuteri. The typical study gives one group reuteri lozenges and the other group identical placebo lozenges for four to twelve weeks, with everyone brushing as normal. The reuteri groups mostly show lower gingival index and bleeding scores, and sometimes lower plaque, than placebo. The differences are statistically real in the better studies. They are also modest. We are talking about meaningful improvement in mild to moderate gingivitis, not a transformation. You can read the abstracts yourself through a PubMed search on probiotics and gingivitis, and I would encourage you to, because the pattern is clearer from twenty abstracts than from any single review.

For bad breath, the evidence is thinner and the strains vary. Some trials of Streptococcus salivarius K12 and of reuteri show reduced sulfur compound readings. Others show nothing. My reading is that probiotics help breath when the source is tongue bacteria and do not help when the source is gum disease, a dry mouth, a sinus problem or the stomach. MedlinePlus's overview of bad breath lists the causes, and only one of them is the kind a probiotic can touch.

What the trials do not show

Nobody has shown that an oral probiotic treats periodontitis, the stage with bone loss. The trials that include periodontitis patients use the probiotic alongside scaling and root planing, and some show a small extra benefit from the combination. None show it working on its own, and I would be very wary of any product that implied otherwise.

Nobody has shown lasting effects after you stop. In every trial that followed up, the scores drifted back toward baseline within weeks of the last lozenge. This is a maintenance product. You are renting the benefit.

And nobody has shown whitening. I mention this because some products in the category, including the one I am about to discuss, put whitening language on the box, and there is no probiotic mechanism for it.

How to use one, if you use one

Timing: after brushing, not before, and ideally at night, so the strains have hours in a mouth that is not eating. Some people take them in the morning for breath and that is reasonable too.

Method: let it dissolve or chew slowly. Do not swallow it whole. Do not rinse or drink for twenty to thirty minutes after. The whole point is contact time.

Duration: give it a month before judging, and two months before deciding. The trials that showed effects ran four weeks at minimum.

Expectations: less bleeding when you floss, a lighter tongue coating, milder morning breath. Not a cure for anything.

The NCCIH's probiotics overview is the best plain-language safety summary I know of. The short version is that these strains are safe for healthy adults and that people with compromised immune systems should ask a doctor first.

My honest take on ProDentim

It is the product patients ask about most, so I read its label with care. It contains Lactobacillus reuteri, which is the strain I would want in any gum product. It contains Lactobacillus paracasei, which has some supporting trials for plaque, and Bifidobacterium lactis BL-04, which has a good safety record but little specific oral evidence. Total count is 3.5 billion CFU, which is in the normal range for an oral product. The rest is inulin, a calcium salt, malic acid and peppermint.

What I liked: the reuteri, the chewable format, the once-a-day dose, and the fact that it does not contain sugar, which would be absurd in a dental product and which some competitors manage to include anyway.

What I did not like: the marketing. The sales page makes whitening claims the ingredients cannot support and uses language about "repopulating" the mouth that overstates what a daily lozenge does. The product is better than its advertising, which is an odd thing to have to say.

What I told patients: if you floss and your gums still bleed a little, or if your breath is a tongue problem and the scraper is not enough, the ProDentim soft tablet is a reasonable thing to try for sixty days. If you do not floss, do that first. If your gums bleed a lot or your teeth move, see the dentist and do not spend money on anything until you have. And whatever you try, write down what changed, because the effects are small enough that you will not trust your memory.

Two things I would want a probiotic maker to tell me

The CFU count per strain, not just the total, since reuteri is doing the work and I want to know how much of it there is. And the CFU guaranteed at the end of shelf life, not at manufacture, since live bacteria die in the bottle over time. Neither is on the ProDentim label. Neither is on most labels in this category. If a product ever lists both, that is the product I would buy without a second thought.

The sentence I ended with

Probiotics are a sixth habit, after flossing, brushing, moisture, fewer sugar hits and tongue cleaning. They are not a shortcut past the first five. If you have the five and you want the sixth, the strain to look for is reuteri, the trial length to give it is two months, and the official product page for the one most people try is at ProDentim's official page. Read the label before you read the testimonials.