Ask the Expert: Do I Really Need to Floss?

Read the interview below with Dr. Tim Iafolla who answers all your common questions about flossing. Dr. Iafolla is the Chief, Program Analysis and Reporting Branch in the NIDCR Office of Science Policy & Analysis.

What is the purpose of flossing?

Timothy Iafolla, DMD, MPH
Timothy J. Iafolla, DMD, MPH

Put simply, flossing cleans between the teeth where brushing can’t reach. The goal is to disrupt the formation of dental plaque before it calcifies to form calculus.

Dental plaque is a sticky biofilm composed of bacteria and food particles that forms on the surfaces of teeth and dental prosthetics such as dentures, implants, or crowns. Plaque can cause gingivitis, an inflammation of the gums. Gingivitis is preventable and reversible by brushing and flossing.

Calculus is plaque that has absorbed calcium from saliva and then hardens. Calculus cannot be removed by brushing and flossing; it must be removed by a dental professional with dental cleaning instruments. If calculus stays in place for a long time, it can cause periodontitis, an inflammatory condition in which gums pull away from the teeth. If not treated, the bones, gums, and tissue that support the teeth are destroyed. Eventually, severe periodontitis leads to loosening of teeth and tooth loss. Periodontitis can take months or years to develop.

How long does it typically take for gingivitis to develop?

The onset of gingivitis can take as little as 24 hours, and calculus can begin to form soon after that—but this is variable from patient to patient. Gingivitis and periodontitis are the body’s inflammatory reaction to plaque and calculus, and some people are more prone to inflammation than others.

I’ve heard there isn’t much evidence that shows flossing is effective. Does that mean it’s ok to skip flossing?

The short answer is no. Cleaning all sides of your teeth, including between your teeth where the toothbrush can’t reach, is a good thing.

Although long-term, large-scale studies of flossing are somewhat limited, researchers have found modest benefits from flossing in small, short-term studies. For example, an analysis of recent studies1 found that home use of floss or interdental brushes in addition to toothbrushing may reduce gingivitis or plaque, or both, more than toothbrushing alone. However, these studies like many past studies, measured outcomes mostly in the short term.

Because these studies are very expensive, and because it can take months or years for periodontitis (the severe form of gum disease) to develop, the studies usually use other end points (plaque development, for example) rather than disease formation. Another challenge is that it’s difficult to document at-home health behaviors of large numbers of study participants over time.

The fact that there hasn’t been a long-term, huge population-based study of flossing doesn’t mean that flossing is not effective. It simply suggests that large, multi-year studies of individual health behaviors (of any kind, flossing included) are difficult and expensive to conduct.

Flossing is a low-risk, low-cost way to clean parts of your teeth where your toothbrush can’t reach.

For folks who really hate flossing, do you have any suggestions?

The first thing to do is to check your flossing technique—your dentist or dental hygienist will be happy to show you some flossing tips and tricks that might make it easier. But there are also other ways to remove plaque from between your teeth, such as with a water flosser, a floss holder, or interdental brushes. The important thing is to disrupt the plaque before it hardens into calculus.

What are common flossing mistakes?

Many people try to floss in front of a mirror, and the reversed image is confusing—it’s difficult to coordinate your hands and eyes when the image is reversed. For some people it’s easier to navigate by feel rather than by sight. It takes practice but soon becomes second nature for most people, especially if you stick to the same flossing pattern (upper jaw, left to right, etc.) and don’t skip around.

Use a piece of floss that’s at least 18” or more, with the unused floss wrapped around the middle and ring fingers of both hands. It’s easier to navigate and control than a short piece of floss. Another common mistake is to snap the floss through the contact area between the teeth.

This can cause pain and damage the delicate tissue between the teeth. It’s better to use a sawing motion to slide the floss through the contact. If you have very tight contacts, another alternative is to use a floss threader to get the floss where it needs to go.

In your personal opinion, how bad is it really not to floss?

Nobody is perfect in all their health habits and behaviors. Like dieting or exercising, skipping a day here and there won’t hurt; in fact, there are some lucky people who have healthy mouths despite never flossing. But a dentist can almost always tell when somebody doesn’t floss. There are usually clear signs when the interdental areas are being neglected—sometimes it’s plaque or calculus buildup, and sometimes it’s a more serious condition like gingivitis or periodontitis. Timely removal of plaque from between the teeth is the goal, whether it’s with floss or some other method like interdental brushes.


  1. Worthington HV, MacDonald L, Poklepovic Pericic T, et al. Home use of interdental cleaning devices, in addition to toothbrushing, for preventing and controlling periodontal diseases and dental caries. Cochrane Database Syst Rev. 2019;4(4):CD012018. Published 2019 Apr 10.
Last Reviewed
April 2022