 Over the years, it's been generally accepted that the use of dental floss has a positive effect, removing up to 80% of plaque. How do we know? You can use what's called a split-mouth design, where each person can act as their own control. For example, only flossing one-quarter of their mouth. They asked study subjects to stop brushing their lower jaw so that plaque would build up. Then they were randomized to floss half and leave the other half as the non-flossed control. After three weeks, not only did the flossing cut plaque about 60%, more importantly it cut signs of gingivitis in half, leading on probing and another index of gum inflammation. Note, though, this is comparing flossing to nothing. They weren't allowed to brush the jaw. So yeah, flossing is better than nothing, but is flossing plus brushing better than just brushing alone? The advocacy of floss hinges on large part on common sense, but common sense doesn't go very far as a form of evidence. You don't really know until you put it to the test. What's the efficacy of dental floss in addition to a toothbrush? Surprisingly, only three out of the 11 studies they looked at found a significant added benefit. The anti-flossers were positively giddy, comparing dentists who continued to advocate flossing in the face of the data to flat earthers. Dentistry is a profession in denial. Over 80% of people don't floss regularly. It's just hard for the dental elite to accept that the great underflossed masses were right and us doctors were wrong. Flossing doesn't work, get over it. So you've heard of the tooth fairy. Is flossing just some tooth fairy tale? This review was published back in 2008. Since then, more studies were published, while the evidence on additional plaque reduction is weak. At least there's some evidence that helps with gingivitis, which is a primary reason you want to reduce plaque anyway. Why might they have not found stronger evidence? Well the trials were of poor quality, and so the conclusions must be viewed as unreliable. So basically, we don't have good evidence either way, because good studies really haven't been done. Why not? Why wouldn't big floss fund the studies? Because it appears that all floss works the same. If you compare unwaxed, to woven, to shred resistant floss, they all have about the same plaque removal efficacy, which it appears all such studies found. So why would a floss company fund a study to show flossing in general is good if they can't show their product is better? Otherwise, you might just go buy their competitors' flaws. Where do we stand today? Although technically, the evidence for flossing is weak, more importantly, the methodology of the studies examining flossing effectiveness are also weak. For example, they didn't assess the quality of people's flossing. This, for example, is not the way to floss. Don't ask the long story. In the bottom line, the American Dental Association continues to recommend brushing and flossing every day. But what's the proper sequence? Should you floss before or after you brush? Some dentists argue that flossing should come first because you stir up the particles and plaque that the toothbrush can then brush away, and then the fluoride from the toothpaste might get in there better. But others recommend brushing first, thinking that that would remove the bulk of the particles first and then the floss could like floss some of the fluoride from the residual toothpaste in there. You don't know, until you put it to the test. The effect of tooth brushing and flossing sequence on between tooth plaque reduction and fluoride retention are randomized controlled clinical trial and flossing first one, in terms of getting rid of significantly more plaque and getting more of the fluoride in there. When we floss after brushing, much of the particles that are being pushed out by dental floss may stay in place on our teeth. The bottom line is flossing, followed by brushing, is preferred.