Flossing is not better than brushing, and brushing is not better than flossing. They do different jobs. Your toothbrush cleans the broad surfaces of your teeth, while floss reaches the tight spaces between teeth where bristles can’t go. Skipping either one leaves a significant portion of your tooth surfaces uncleaned.
What Each One Actually Does
Brushing removes the sticky film of bacteria (plaque) from the front, back, and chewing surfaces of your teeth. It also delivers fluoride from toothpaste, which strengthens enamel and helps prevent cavities. But even the best brushing technique can’t reach the contact points where two teeth press together or slip below the gumline between teeth.
Flossing targets exactly those gaps. The spaces between your teeth make up roughly 30 to 40 percent of total tooth surface area. Plaque that builds up in these areas causes gum inflammation and, over time, cavities that form on the sides of teeth rather than the tops. These between-teeth cavities are harder to spot early and often require more complex dental work to fix.
What the Evidence Shows
A 12-week clinical trial published in the Journal of Dental Hygiene found that adding flossing to brushing reduced gum inflammation by about 9% and gum bleeding by roughly 17% compared to brushing alone. Interestingly, flossing didn’t significantly reduce overall plaque scores in that study, which suggests its primary benefit is protecting gum health rather than cleaning visible tooth surfaces.
A Cochrane review looking across 12 studies reached a similar conclusion: flossing plus brushing consistently reduced gingivitis compared to brushing alone, and the benefit grew larger over time. At one month, the improvement was modest. By six months, it was substantially greater. However, the review noted that the overall quality of flossing studies has been poor, making it hard to pin down exact numbers with confidence.
For cavity prevention specifically, research from the American Academy of Pediatric Dentistry found that regular interdental flossing reduced between-teeth cavities by 30 to 55 percent, depending on the study. The Cochrane review, though, noted that no high-quality adult trials have directly measured flossing’s effect on cavities. The cavity-prevention evidence is strongest in children whose teeth were flossed by trained dental professionals.
Why Brushing Still Matters More
If you had to choose only one, brushing wins. It covers more tooth surface, delivers fluoride, and is the single most effective thing you can do to prevent both cavities and gum disease. No dentist would tell you to floss instead of brushing. But that’s a false choice for most people. The American Dental Association recommends cleaning between your teeth daily alongside twice-daily brushing, because each tool handles a job the other can’t.
Think of it this way: brushing without flossing is like washing only the front and back of your hands but never between your fingers. You’re doing most of the work, but you’re consistently missing the same spots every time. Those neglected areas accumulate bacteria day after day, which is why gum disease and between-teeth cavities tend to develop in predictable locations.
Floss Before You Brush
If you do both, sequence matters. A clinical trial that tested both orders found that flossing first, then brushing, removed significantly more plaque than brushing first. The likely reason is straightforward: flossing loosens debris and bacteria from between teeth, and brushing afterward sweeps those particles away. Rinsing with water after brushing further clears the mouth.
There’s a bonus to this order. The study also found that fluoride from toothpaste remained at higher concentrations between teeth when participants flossed first. Flossing clears the gaps so fluoride can actually reach those surfaces during brushing.
Interdental Brushes as an Alternative
Traditional string floss isn’t the only option for cleaning between teeth. Small interdental brushes, sometimes called proxy brushes or interproximal brushes, are tiny bottle-shaped brushes designed to slide between teeth. Multiple studies have found that interdental brushes remove more plaque from between teeth than string floss, particularly for people with gum disease or naturally wider gaps between teeth. A 2015 meta-review in the Journal of Clinical Periodontology concluded there is moderate evidence that interdental brushes are among the most effective tools for between-teeth plaque removal.
That said, the advantage narrows in real-world use. A 2024 study found that when people used these tools at home without professional supervision, the improvements in gum inflammation were small and nearly identical for floss (about 2.8%) and interdental brushes (about 2.6%). The best interdental tool is the one you’ll actually use consistently. If your teeth are tightly spaced and floss slides through easily, floss works well. If you have wider gaps, bridges, or braces, interdental brushes may be easier and more effective.
Making It Count
Most people brush regularly but floss sporadically, and the research suggests this pattern shows up in their dental health. The consistent finding across studies is that adding any form of interdental cleaning to brushing produces measurable reductions in gum bleeding and inflammation. The specific tool matters less than the habit.
For brushing, two minutes twice a day with fluoride toothpaste covers the essentials. For flossing or interdental cleaning, once daily is sufficient. Plaque takes roughly 24 hours to mature into the kind of bacterial colony that damages gums, so a daily disruption between teeth keeps it from gaining a foothold. If you’re only doing one of these things, you’re leaving a meaningful portion of the job undone.