Brushing our teeth is so deeply ingrained in us that we don’t even think about it usually. You put toothpaste on, brush your teeth for around two minutes, rinse and go on with your day. But, umm, that’s apparently not how you’re supposed to do it.
Dentists who researched this issue have a surprising takeaway message: after you brush, spit — but don’t rinse. That small shift can keep a protective film of fluoride on your teeth for longer, tipping the balance from decay toward repair. Yes, really.
Why You Probably Shouldn’t Rinse
Your mouth is a complex ecosystem. Your teeth are covered by oral bacteria, which form a sticky biofilm known as dental plaque. These bacteria consume dietary sugars and generate acids that lower the pH at the tooth surface. If this process outpaces natural remineralization, it can cause the enamel crystals to dissolve.
Fluoride changes that chemistry and helps your teeth remineralize. It slows mineral loss during acid attacks and speeds repair when the pH rises. In the presence of fluoride, rebuilding enamel forms a tougher mineral, fluorapatite, which resists acid down to roughly pH 4.5. Each exposure adds a little more armor, and fluoride also has a direct antimicrobial effect on the bacteria that cause caries.
That’s why brushing your teeth is so important. But to work best, fluoride has to linger around. Higher levels that fall more slowly mean better protection across the day. This is where rinsing comes in.
Rinsing with water after brushing drains that reservoir. You dilute the beneficial high-concentration fluoride from the toothpaste and replace it with a non-therapeutic liquid, effectively nullifying the primary benefit of the fluoride toothpaste. Your saliva also plays a role in maintaining oral health, but it’s nowhere near as effective as fluoride.
No-rinse methods consistently leave more fluoride to protect your teeth. So after you brush, the best thing to do isn’t to rinse, but rather to spit out the excess toothpaste and leave the fluoride work its magic.
What Studies Found
If you’re like me (or most people), you’ve been taught that rinsing is good after brushing. So, how consistent is the evidence?
Several clinical trials have been conducted to specifically measure how rinsing with water affects the post-brushing fluoride reservoir. The evidence is remarkably consistent and points to a significant detrimental effect.
One of the most rigorous early looks came from researchers at Göteborg University in Sweden. In a randomized crossover trial, dental students brushed with fluoride toothpaste and then followed different rinsing routines. Rinsing with a large volume of water — three 10 mL swishes — cut fluoride levels in saliva, interdental fluid, and plaque far more than a single 5 mL rinse. The time spent rinsing, whether 10 or 60 seconds, barely mattered. What counted was the water volume. So basically, the larger the volume of water you use for brushing teeth, the more you dilute the fluoride.
Another 2009 study found that participants who rinsed with water after brushing had a markedly steeper fluoride clearance curve, with fluoride levels often returning to baseline within 30 minutes. Those who only spat retained therapeutic fluoride levels well beyond that window. Another crossover study confirmed that not rinsing increases fluoride concentration in the mouth and also confirmed that the fluoride stays locally in the mouth and doesn’t appear in blood levels.
A commonly-cited study had less clear evidence. A three-year trial in Kaunas, Lithuania, had 407 schoolchildren brush their teeth daily under supervision with a 1,500 ppm fluoride toothpaste. One group rinsed thoroughly with a beaker of water; another group spat only. Both groups developed far fewer cavities than a control school with no daily brushing. But between the rinse and no-rinse schools, cavity rates didn’t separate significantly.
However, researchers attributed this to the powerful effect of daily supervised fluoride use. Basically, this had such a powerful positive impact that it overwhelmed subtle differences in rinsing habits.
Herein lies another subtle point: the big thing is brushing your teeth. Rinsing or not rinsing is secondary. It’s better not to rinse, but as long as you’re brushing your teeth constantly and properly, you should be fine.
Public Health Bodies Have a Consistent Message
Different health bodies and dental associations from around the world also have a remarkably consistent message.
The United Kingdom’s National Health Service (NHS) has been particularly clear and proactive. Across its various platforms and informational materials, the NHS provides unambiguous guidance. The official recommendation for adults is to “spit out any excess toothpaste. Do not to rinse your mouth out straight away”. The rationale provided by the NHS is directly aligned with the scientific evidence on fluoride kinetics: rinsing “will wash away any fluoride left over from your toothpaste, reducing benefit to your dental health”. Various
In the United States, the American Dental Association (ADA) has a similar message, suggesting that individuals should spit out any remaining toothpaste but explicitly “avoid the use of water”. This recommendation is based on the same principle. Universities from Europe to the US to the Philippines have all independently arrived at the same conclusion and have proposed similar guidance.
Reconsidering the Ingrained Habit
So then, why do so many people still rinse?
The simple answer is because that’s how we were taught; and there’s a good reason why that’s how we were taught.
Ingesting fluoride is not a concern in adults. Studies have shown that fluoride stays locally and causes no detectible change if you don’t rinse. However, for children (and young children in particular), who are more sensitive and also have a less refined swallowing reflex, it’s a logical concern. So, we teach children to rinse after they wash their teeth to avoid swallowing toothpaste. That habit stays with many of us throughout our adulthood.
But we should revisit it when we grow up.
A large body of published science demonstrates that rinsing the mouth with water or even mouthwash immediately after brushing significantly reduces the intraoral fluoride reservoir. This action reduces the benefits provided by fluoride toothpaste.
So, if you want the absolute best for your oral hygiene, spit but don’t rinse.
