To rinse or not to rinse? You might be brushing your teeth wrong.

Any good dentist would tell you that oral health starts with brushing teeth. It’s a habit ingrained in us since early childhood, and as adults, the routine hasn’t changed much. Add a pea-sized amount of toothpaste and gently brush in soft circles for at least two minutes. It’s the two minutes after brushing that’s stirring up discussion on TikTok. 

Many people rinse their mouths after brushing their teeth, but some TikTokers argue it’s healthier to only spit out the excess toothpaste. By not rinsing, they claim, you would allow the toothpaste’s ingredients to exert their effects for longer. 

Though TikTok hasn’t always been the most reliable source for dental news—remember when people were giving DIY advice on how to file down teeth—this information is an exception, and something the dentists PopSci spoke to support.

First, let’s consider why we brush our teeth. Dr. Kacie Woodis, a clinical assistant professor at the University of Minnesota School of Dentistry, says that when we eat, so do the approximately 1,000 species of bacteria living in our mouths. These microbes have a strange way of thanking us for the meal. Some bacteria in the back of the tongue, for example, interact with amino acids from the food, producing sulfur-producing compounds that cause bad breath. Other bacterial species produce an acid that can break down minerals and dissolve a tooth’s surface, starting cavity formation. 

[Related: The best cheap electric toothbrushes]

Fluoride, a mineral found in most toothpastes, builds resistance against acid attacks. It does so by aiding in a repair process called remineralization. 

“Fluoride counteracts the demineralization process by partnering with calcium and phosphate to form fluorapatite,” explains Dr. Fatima Khan, a dentist and cofounder of Riven Oral Care in Texas. “Fluorapatite is a crystalline lattice that covers the enamel to remineralize it and restore its integrity.” The longer fluoride sits on your teeth, the more effective it is at creating stronger teeth (so long as you’re only using the recommended pea-size amount of toothpaste to brush). 

The American Dental Association recommends brushing for a full two minutes. However, most people brush for less than the recommended time, for about 45 to 70 seconds a day. Brushing less than two minutes means people are not getting the benefits of fluoride toothpaste, says Khan. 

Spitting instead of rinsing toothpaste gives fluoride more time to assist with the remineralization process—especially since tooth enamel cannot grow back once it is completely destroyed. Woodis recommends everyone spit instead of rinse, especially among people at high risk for cavities. “We’ll prescribe an extra-strength fluoride toothpaste, and we often recommend that people spit and not rinse that prescription toothpaste.”

If you’re a mouth rinser, spitting may not sound the most hygienic. You might imagine loose bacteria and food still trapped in your mouth. If that’s the case, Khan says to floss first and then rinse your mouth with water. This would flush out any residual food and plaque buildup prior to brushing your teeth. 

Another concern is residual charcoal on teeth if using charcoal toothpaste. Both Woodis and Khan warn against using charcoal-based toothpaste in the first place. The material is too abrasive and can strip away tooth enamel, eventually turning teeth yellow.

Some people rinse their mouths for medical reasons. People sensitive to sodium lauryl sulfate (SLS), another common ingredient in toothpaste, can produce canker sores and skin peeling inside the mouth when exposed to it for a prolonged time. Additionally, some people may develop a rash around their mouth called perioral dermatitis from fluoride, SLS, and cinnamon flavorings in toothpaste. Khan says these folks should switch to a natural toothpaste containing hydroxyapatite and wash their face after brushing to wipe off any excess paste.

If you still want to rinse your mouth, Woodis advises delaying it for 20 to 30 minutes to maximize fluoride’s effects. Even if you wanted to rinse with a fluoride-based mouthwash, she says it would be better to wait instead of immediately rinsing since it has a lower fluoride concentration. She says most over-the-counter toothpaste has a fluoride content of around 1000 to 1500 parts per million, whereas most fluoride mouthrinses are usually 100 to 200 parts per million.

The bottom line is the choice is up to you whether you want to spit or rinse after brushing. Your dentist will probably not hold it against you at your next appointment. Although they might raise an eyebrow if you tell them you’re getting dental information from social media.