The best order is floss first, brush second, and use mouthwash at a separate time. While the American Dental Association says either flossing or brushing can come first “as long as you do a thorough job,” clinical research points to a clear winner when it comes to sequence.
Why Flossing First Works Better
A randomized controlled clinical trial published in the Journal of Periodontology compared two groups: one that flossed before brushing and one that brushed before flossing. The floss-first group had significantly greater reductions in both interdental plaque (the buildup between teeth) and overall plaque compared to the brush-first group.
A second clinical trial, conducted as a crossover study where the same participants tried both sequences, confirmed the finding. Plaque scores were significantly lower during the floss-then-brush phase than during the brush-then-floss phase.
The logic is straightforward. Flossing loosens debris and bacteria from between your teeth and along the gumline. When you brush afterward, the fluoride in your toothpaste can reach those newly cleaned surfaces. The first study measured this directly: fluoride concentrations in the plaque between teeth were significantly higher when people flossed before brushing. In the reverse order, the toothpaste’s fluoride has already come and gone before flossing opens up those tight spaces.
Where Mouthwash Fits In
This is where most people get the sequence wrong. It feels natural to rinse with mouthwash right after brushing as a finishing step, but doing so actually undermines your toothpaste. The NHS specifically advises against using mouthwash, even a fluoride one, straight after brushing because it washes away the concentrated fluoride left on your teeth from the toothpaste. That residual fluoride is doing important work: it continues to strengthen enamel and fight decay for some time after you spit.
The same principle applies to rinsing with water. Spit out the excess toothpaste, but skip the rinse. This keeps the fluoride concentration high on your tooth surfaces where it matters most. Research published in the British Dental Journal found that post-brushing rinsing behaviors vary widely in the general population, but consistently, rinsing too soon reduces the cavity-preventing benefit of fluoride toothpaste.
If you want to use mouthwash, wait at least 30 minutes after brushing, or better yet, use it at a completely different time of day. Lunchtime or after an afternoon snack is a good option. This gives you the antibacterial or fluoride benefits of the rinse without canceling out the benefits of your toothpaste.
The Ideal Routine
Putting it all together, a practical daily routine looks like this:
- Step 1: Floss. Work the floss between every pair of teeth, curving it into a C-shape against each tooth surface and sliding it below the gumline. This dislodges plaque and food particles so your toothbrush and toothpaste can do their job.
- Step 2: Brush for two minutes with a fluoride toothpaste. After brushing, spit but don’t rinse with water.
- Step 3: Use mouthwash later. Wait at least 30 minutes, or save it for a different time of day entirely.
You only need to floss once a day, but you should brush twice. So your morning routine might be floss then brush, your evening routine just brush, and your mouthwash use fits in somewhere in between.
What About Pre-Brushing Mouthwash?
Some mouthwash products are marketed as “pre-brushing rinses,” claiming to loosen plaque so brushing removes more of it. The evidence doesn’t support this. A controlled study comparing a pre-brushing rinse (Plax) to a placebo solution found no difference in plaque removal. The rinse removed 40% of plaque from tooth surfaces, the placebo removed 42%, a statistically identical result. Your time is better spent on thorough flossing before you pick up the toothbrush.
Consistency Matters More Than Perfection
The research favoring floss-before-brush is real, but the margins aren’t dramatic enough to stress over if the reverse order is what keeps you flossing at all. The ADA’s position reflects this: doing both thoroughly matters more than the sequence. The people who benefit most from optimizing the order are those who already have an established routine and want to squeeze more protection out of it.
That said, if you’re building a habit from scratch, you might as well build the better one. Floss, brush, spit without rinsing, and save the mouthwash for later. It takes no extra time and gives the fluoride in your toothpaste the best chance of protecting your teeth.