Q: Should I rinse—or not—after I brush my teeth? I hear conflicting advice. Labels do warn not to swallow fluoride toothpaste.
A: First, what’s most important is just to brush—at least twice a day with fluoride toothpaste, using proper technique. That said, to retain more fluoride in your mouth, you should rinse with as little water as possible, especially if you are prone to cavities.
Several studies have found that less is more when it comes to rinsing. For instance, in a small study in the International Dental Journal in 2013, rinsing once after brushing resulted in higher fluoride retention than rinsing three times.
Better yet, you can rinse your mouth with a toothpaste “slurry,” which simply means sipping a tiny amount of water and mixing it with the toothpaste foam in your mouth; briskly swish the slurry around and then spit it out with no further rinsing. In a Swedish study in Caries Research in 1996, people who rinsed with a toothpaste slurry (made with one teaspoon of water) for one minute had higher concentrations of fluoride in the plaque between teeth than those who did three quick rinses with more water. This may have practical value, since ordinary toothbrushing doesn’t clean those areas well.
The same Swedish researchers found that preschoolers who were instructed to rinse with a toothpaste slurry had fewer cavities over three years than children who rinsed as usual.
Another option is to use a fluoride rinse after brushing (with or without rinsing first with water). Be aware that nonfluoride mouth rinses will rinse away much of the fluoride from the toothpaste, however—so if you use one, do so before you brush or at a different time than brushing.
As for the caution not to swallow toothpaste, that’s because too much fluoride can cause fluorosis (spotting or discoloration) in developing teeth. Very high doses (far beyond normal usage) can be toxic. Parents should supervise young children when they brush, especially to make sure they use just a pea-sized dab of toothpaste.