Why dentists say you shouldn’t rinse after brushing

The question:

Is it true that you shouldn’t rinse after brushing your teeth?

The science:

Viral TikTok videos have challenged the way many people brush their teeth. Their advice: Brush your teeth with a fluoride-containing toothpaste and spit - but don’t rinse.

Dental experts agree. They recommend brushing at least twice a day with a fluoride-containing toothpaste to help prevent cavities. And they say skipping the rinse after brushing allows the fluoride to stay on the teeth, providing added protection.

Those who prefer to rinse should rinse lightly with a small amount of water such as a sip from the hand or delay the rinse by about 20 minutes, said Brittany Seymour, a spokeswoman for the American Dental Association (ADA) and an associate professor at Harvard School of Dental Medicine.

A 1999 study of more than 2,800 teenagers - age 15 and 16 - in the United Kingdom found that those who rinsed with a cup of water after brushing had an average of almost four decayed, missing or filled teeth compared with about three for those who did not rinse at all. Those who rinsed with less water, for example from their hand, had about 3.62 bad teeth.

Skipping the rinse is not essential for people with healthy teeth, but those who eat a high-sugar diet or are prone to cavities may need extra help from the fluoride, said Margherita Fontana, a professor at the University of Michigan School of Dentistry. “When you rinse, you are basically rinsing away the active ingredients of the toothpaste that you just put on your teeth,” she said.

Another option for those who want to rinse after brushing is to follow up with a mouthwash containing fluoride, Fontana said.

Dental plaque is covered with certain acid-producing bacteria that, with help from a sugar-rich diet and poor oral hygiene, can cause cavities. Fluoride, a mineral, helps prevent cavities by protecting the teeth - primarily by helping to replace minerals that have been lost from the protective enamel and to reduce the amount of minerals the enamel loses.

While fluoride is essential for protecting teeth, ingesting excessive amounts may increase the risk of fluoride toxicity. Ingesting too much fluoride over an extended period during tooth development in early childhood can cause white spots to form on the permanent teeth, a cosmetic condition called fluorosis, but it is usually mild in the United States.

Dental experts say the amount of fluoride that would be left on your teeth after brushing is safe, though children should always be supervised when brushing to make sure they do not ingest too much of it.

What else you should know:

The same brushing habits are suggested for children.

Fluoride-containing toothpaste is recommended as soon as they cut their teeth. For children younger than 3, caregivers should brush the teeth with a smear of toothpaste “the size of a grain of rice,” and those age 3 to 6 should be given no more than a pea-size amount, according to the ADA and the American Academy of Pediatric Dentistry (AAPD).

Then parents and caregivers should have their children spit out as much as possible to avoid swallowing it, but keep the remaining fluoride on their children’s teeth to help protect against cavities, said Scott Cashion, a pediatric dentist and president of the AAPD.

“We recommend that they spit it out but try not to rinse it,” he said. “When they go off to bed, if there’s fluoride on those teeth, it’s going to help protect them through the night.”

The bottom line:

Skipping the rinse after brushing with a fluoride-containing toothpaste - or rinsing lightly or delaying the rinse - allows the fluoride to stay on the teeth, providing added protection.

Lindsey Bever is a reporter for The Washington Post’s Well+Being desk, covering chronic illness, mental health and navigating the medical system, among other issues. She was previously a reporter at the Dallas Morning News.