Brushing alone may remove only up to about 60% of plaque at each session, according to a peer-reviewed review in Dentistry Journal.1 The plaque it leaves behind isn't scattered at random: it concentrates in the tight spaces between teeth, exactly where most gum disease and between-the-teeth decay begin.
Is brushing enough on its own?
No: even done well, it doesn't finish the job. Give brushing its due first: it's arguably the most successful health habit ever taught at population scale: almost everyone brushes daily, without reminders, without willpower, as automatically as locking the front door. Decades of dental advice built a behavior that actually stuck.
Which makes the next fact all the more important. A peer-reviewed review of interdental cleaning methods in Dentistry Journal estimates that brushing alone may remove only up to about 60% of plaque at each session.1 Read that carefully: the everyday habit nearly all of us rely on as our entire oral-hygiene routine addresses, at best, a bit more than half of the problem it exists to solve.
Brushing is necessary. It just isn't sufficient. Up to about 40% of plaque can be left behind after even a good brushing, and it isn't left behind at random.
Where does the rest of the plaque go?
It concentrates in the interproximal spaces (the tight contact areas between neighboring teeth and the little valleys of gumline between them) rather than scattering evenly around the mouth. Bristles are simply the wrong shape for those spaces: they splay across the outer and chewing surfaces but can't slide between two teeth that touch.
And those between-the-teeth zones are not a minor corner of the mouth. They're precisely where much of the trouble starts. Plaque left along and below the gumline between teeth is what drives gum inflammation (the earliest stage of gum disease), and the contact points between teeth are where interproximal decay, the between-the-teeth cavities, takes hold. In other words, the plaque that brushing leaves behind sits exactly where most gum disease and between-the-teeth decay begin.1
This is why the between-the-teeth spaces need their own habit, with their own tools: floss, interdental brushes, or a water flosser. A toothbrush was never designed for that geography, and no amount of extra brushing time changes its shape.
How reliable is the 60% figure?
It supports one phrasing and not another, because this statistic gets mangled as it travels. You'll sometimes see it quoted as "brushing only cleans 60% of tooth surfaces," stated as hard fact. That's not quite what the evidence supports. The defensible, peer-reviewed version is the one above: brushing alone may remove only up to about 60% of plaque at each episode: an estimate from a published review, with "up to" and "about" doing real work in the sentence.1
The precise figure matters less than what it tells you either way: a meaningful share of plaque routinely survives brushing, and it survives in the highest-risk locations. That conclusion is robust even if the exact percentage varies from mouth to mouth and study to study.
How many people actually clean between their teeth?
Only about one in three American adults do it daily, according to CDC survey data, a figure that has barely moved in over a decade.2 Put that next to the behavior data on brushing and the two stories collide: brushing, the habit that handles part of the mouth, is nearly universal; interdental cleaning, the habit that handles the part where most trouble begins, is the minority habit. We unpack that number, and why the real figure is probably lower, in only about 1 in 3 adults floss daily.
So the standard American oral-care routine, for roughly two out of three adults, consists entirely of the tool that leaves the between-the-teeth plaque in place. Meanwhile, by the CDC's own measurement, about 42% of adults over 30 have some form of gum disease.3 No single statistic proves the connection, but the geography lines up: the disease is concentrated where the unbrushed plaque sits, and most adults have no daily habit that reaches it.
Does adding interdental cleaning actually help?
The honest answer is encouraging without being miraculous. In large national survey data, adults who clean between their teeth regularly have measurably less gum disease, and the most frequent cleaners have the least severe disease: an association, not a guarantee, but a consistent one.4 We examine that evidence in detail in regular interdental cleaning and lower odds of gum disease.
To be precise about what the science supports: cleaning between your teeth is associated with less gum disease, and clinical trials show it reduces gum inflammation, the earliest stage of gum disease. No one can honestly promise you it prevents or cures anything. What the evidence does say is simpler: brushing addresses part of the mouth's plaque, the remainder sits in the highest-risk spots, and the only habits that reach those spots are the interdental ones. Brushing was the first half of the routine we all learned. This library exists because most of us never picked up the second half.
Common questions
Does brushing really only clean 60% of your teeth?
Not quite: that's the mangled version. The peer-reviewed estimate is that brushing alone may remove only up to about 60% of plaque at each episode, with "up to" and "about" doing real work in the sentence.1 It's an estimate from a published review, not a fixed measurement of tooth surfaces.
Where does the plaque a toothbrush misses end up?
In the interproximal spaces: the tight contact areas between neighboring teeth and the gumline valleys between them. Bristles splay across the outer and chewing surfaces but can't slide between two teeth that touch. Those same zones are where gum inflammation and between-the-teeth decay begin.1
Can I just brush longer instead of cleaning between my teeth?
Extra brushing time doesn't change the shape of a toothbrush. Bristles can't enter the contact areas between teeth that touch, so plaque there survives regardless of how long you brush. Reaching those spaces takes a tool built for them: floss, an interdental brush, or a water flosser.
Does cleaning between your teeth reduce gum disease?
In large national survey data, adults who clean between their teeth regularly have measurably less gum disease, and the most frequent cleaners have the least severe disease. That is an association, not a guarantee.4 Clinical trials show interdental cleaning reduces gum inflammation, the earliest stage. Nobody can honestly promise it prevents or cures anything. Details in regular interdental cleaning and lower odds of gum disease.
How does the 60% figure connect to gum disease rates?
By location rather than by proof. About 42% of American adults over 30 have some form of gum disease by the CDC's measurement,3 and roughly two out of three adults have no daily interdental habit.2 No single statistic proves the connection, but the disease is concentrated in the same places the unbrushed plaque sits.
- Ng E, Lim LP. An overview of different interdental cleaning aids and their effectiveness. Dentistry Journal, 2019. PMC6630384. Review estimate: "brushing alone may only remove up to 60% of overall plaque at each episode."
- Fleming EB, et al. Prevalence of daily flossing among adults, NHANES 2011–2014. Journal of Periodontology, 2018. CDC authors. PMC6434526. Self-reported survey data; confirmed by Liang L, Aris IM, JADA 2024, NHANES 2009–2020. PubMed 38752966.
- Eke PI, et al. / CDC. Periodontitis prevalence among US adults, NHANES 2009–2014; NIDCR data pages (2024).
- Marchesan JT, et al. Interdental cleaning is associated with decreased oral disease prevalence. Journal of Dental Research, 2018. PMC6728587. Observational association.