Water Flosser or Dental Floss: Which Removes Plaque and Gum Inflammation Better?

Dental plaque is a biofilm — a layer of bacteria surrounded by their own matrix that rebuilds on the teeth within hours. When it accumulates at the gum margin, the body reacts with inflammation: the gums turn red, swell and bleed easily. This is gingivitis, a stage that is fully reversible if plaque is removed regularly. Left untreated, in some people it can progress to periodontitis, which destroys the bone supporting the teeth and is a chronic disease.

A toothbrush — manual or electric — cleans the cheek-side, tongue-side and chewing surfaces well, but the bristles physically do not enter the narrow gaps between the teeth. That is exactly where plaque lingers longest and where gum inflammation and decay between the teeth most often begin. Hence the idea of adding a tool dedicated to the interdental spaces to brushing.

It is worth stating up front what these data do not cover. The Cochrane review discussed below did not find a single trial assessing the effect of such cleaning on decay between the teeth, and most trials did not assess periodontitis. The results therefore mostly concern short-term measures of gum and plaque status, not keeping your teeth for decades.

Dental floss works mechanically: slipped between the teeth and guided in a C shape along the tooth surface, it scrapes off the biofilm. Its advantage is access to very tight contacts between teeth; its drawback is technique. Floss that is used poorly (jerked, pushed into the gum instead of being fitted to the tooth surface) removes less plaque and may irritate the tissue. Many people give it up after a few weeks because it is a nuisance.

An interdental brush is a tiny brush (usually on a wire) of a defined diameter that you slide into the space between teeth and move back and forth. It requires the gap to be wide enough for the brush to enter without being forced — sizes are matched to the specific spaces, and one mouth often needs two or three different ones. Its strength is that it mechanically cleans concave tooth surfaces that flat floss may not reach.

A water flosser (oral irrigator, or dental water jet) works differently: a pulsating stream of water flushes out debris and partly disrupts the biofilm hydrodynamically, without touching the tooth surface. It is easier to use with braces, bridges and implants, and for people with limited hand dexterity. Its limitation is that liquid does not scrape off adherent biofilm as effectively as mechanical contact — and that is exactly where the doubt arises as to whether flushing matches wiping.

How to read this? First, the direction is consistent: adding anything to brushing alone does not look harmful and in most comparisons gives a small improvement. Second, the size of that improvement is modest, and the certainty of the evidence was rated low or very low — mainly because the trials were short, participants could not be blinded, and many people started with fairly healthy gums, so they had little to improve.

Third — and this matters for answering the question in the title — in head-to-head comparisons interdental brushes did better than floss on gum inflammation, and in single comparisons with floss the irrigator could give a better result after a month, but with very low certainty of evidence and no advantage for plaque. This is not a verdict in favour of the water flosser, but a signal that the data are insufficient for strong conclusions.

From the Cochrane review it follows that interdental brushes may reduce gum inflammation more than floss after one month and after three months, although the evidence has low certainty, and for plaque the results were inconsistent. No difference in periodontal pocket depth was shown, but that is an indicator that changes slowly and rarely differs in short trials.

Why might brushes win? First, a simpler technique: you slide it in and move it, without wrapping floss around your fingers and guiding it in a C shape. Second, better cleaning of concavities — in many places between the teeth the root surface is not flat, so floss can glide over it without touching the biofilm in the hollows. Third, probably better acceptance: a more convenient tool is usually used more often (this is practical reasoning, not a finding of the review), and in oral hygiene regularity matters more than the theoretical effectiveness of a single use.

There are, however, two limitations. A brush needs a space of the right size — where teeth touch tightly, the brush simply will not go in and floss remains the only choice. In addition, the size has to be chosen, and a badly matched brush (too thick, forced in) can irritate the gum. A dentist or hygienist can match the right diameters, and that is one of the few things really worth doing in the surgery instead of buying at random.

Water flossers are advertised as more effective than floss and interdental brushes, often citing manufacturer-funded studies. One such trial (an RCT from 2024, 372 participants with moderate to severe gingivitis, 6 weeks; the authors were employees of the device manufacturer) showed a 29.1% reduction in gum inflammation in the irrigator group, versus −2.1% with brushing alone, 2.8% with floss and 2.6% with an interdental brush. Such numbers are impressive, but they must be read with caution.

Independent meta-analyses give a more restrained picture. In a review of 18 randomised trials covering patients with and without orthodontic appliances (2025), a water jet was comparable to floss for gum inflammation and gave a slight advantage over brushing alone in the short term; the authors concluded that including a water flosser in daily hygiene is justified. In contrast, a meta-analysis of 7 trials in people with braces (2024) found no statistically significant improvement after adding a water flosser to a manual or electric toothbrush (for example a bleeding index difference of −0.05; 95% CI −0.12 to 0.01), with low or very low quality of evidence.

Two reviews from a similar area thus reach slightly different conclusions — which is typical when trials are few, small and differ in protocol. The honest summary is: a water flosser probably does no harm and is sometimes at least as good as floss for controlling gum bleeding in the short term, but there is no solid evidence that it is better than floss.

There are situations in which using floss is difficult or impossible, and there the discussion about minimal differences in trials gives way to practicality. Fixed orthodontic braces make it hard to pass floss between the teeth (a threader is required), and bridges and teeth with implants have spaces into which tools must be introduced at a different angle. Here a water flosser is simply more convenient — and convenience translates into regularity.

The evidence for implants is even more modest. A 2025 review on inflammation of the tissue around implants found 6 relevant trials, only two of which were suitable for meta-analysis. Irrigators and interdental brushes performed slightly better than floss, but the differences were not statistically significant, and the authors stressed that evidence on self-performed hygiene around implants is limited. The practical conclusion: around implants and prosthetic work, the choice of tool should be agreed with a dentist or hygienist, because geometry matters more here than general statistics.

The same goes for patients after periodontitis treatment. A 2020 review of people in the maintenance phase (16 publications) indicated that interdental brushes removed plaque better than brushing alone, and the irrigator gave a favourable effect on inflammation and pocket depth in two of three comparisons — but the authors judged the evidence too sparse and of low certainty to name a single best device.

A good way to check whether the chosen tool works is to observe your own gums. After 2–4 weeks of regular, gentle cleaning of the interdental spaces, the gums should be paler, less swollen and bleed less often. If not, despite correct technique, it is worth asking the dentist whether the cause lies elsewhere — in tartar that has to be removed in the surgery, in leaking fillings, or in a systemic factor.

No tool will remove tartar — hardened plaque that requires professional scaling. If the gums have been inflamed for years and tartar is visible, the first step is the surgery, and only then maintaining the result at home. We write more about the links between gum health, diabetes and the oral microbiome in our knowledge-base entries.

If we had to give a single practical rule, it would be this: start with the tool that suits your teeth and that you will use without forcing yourself. If you have wider spaces, interdental brushes will most likely work best. If your teeth are set tightly, floss remains. If you wear braces, have bridges or have manual difficulties, a water flosser makes a lot of practical sense, even if the evidence for its superiority is weaker than its reputation.

In none of the comparisons did adding interdental cleaning to brushing look harmful, and in most it gave a small, short-term improvement. That is an honest reason to spend two minutes on it every day — but not a reason to spend money expecting miracles from an expensive device.