A report on dental health published by the Associated Press goes against everything your dentist has ever told you.

Despite the persistence of the American Dental Association and the U.S. Surgeon General, there is "little proof" that flossing actually helps in preventing gum disease and cavities.

Wait, what?

Yes, you read that right. "The AP looked at the most rigorous research conducted over the past decade, focusing on 25 studies that generally compared the use of a toothbrush with the combination of toothbrushes and floss," according to the report. "The findings? The evidence for flossing is 'weak, very unreliable,' of 'very low' quality, and carries 'a moderate to large potential for bias.'"

How so? Well, it comes down to basically five factors.

1. The benefits may exist, but are so "minute" that the average person wouldn't notice.

2. The studies use "outdated" methods.

3. The studies don't use a large enough sample size.

4. The studies did not span a long enough time to make any significant claims.

5. The studies are heavily biased because some flossing companies design them.

For example:

"[...] most of these studies used outdated methods or tested few people. Some lasted only two weeks, far too brief for a cavity or dental disease to develop. One tested 25 people after only a single use of floss. Such research, like the reviewed studies, focused on warning signs like bleeding and inflammation, barely dealing with gum disease or cavities."

And in terms of possible bias, it's important to note that one major study, which was discounted in 2011, was supported heavily by Procter & Gamble, which makes some of the $2 billion — yes, billion — generated by the dental/oral health industry. Proctor & Gamble owns Crest and Oral-B. They are not the only ones who depend on these studies:

"Johnson & Johnson spokesman Marc Boston said floss helps remove plaque. When the AP sent him a list of contradicting studies, he declined comment."

Companies regularly fund flossing studies, according to dentist Marcelo W.B. Araujo, vice president of the ADA's Science Institute, who also worked as an executive for Johnson & Johnson, which makes the Reach flossing brand.

So should we abandon flossing forever?

Well, flossing is definitely handy when you have something stuck in your teeth, provided you use the recommended "up-and-down" motion as opposed to a "sawing" motion. As for doing it every day, that's the real question.

The ADA released a statement maintaining that "interdental cleaners" (their fancy term for floss) are "an essential part of taking care of your teeth and gums."

Tim Iafolla, a dentist at the National Institutes of Health, thinks that we shouldn't give up on flossing. "It's low risk, low cost. We know there's a possibility that it works, so we feel comfortable telling people to go ahead and do it."

[h/t AP]