Do I need to floss my teeth?


As a general dentist, this is a question that comes up every day. Sort of. To be honest, I’m not actually asked this question EVERY day (including weekends), in fact, I’m rarely asked it directly. What does happen virtually every time the subject of flossing comes up in my practice, however, is that I can see the question in my patient’s eyes. I can read it in their body language. The reluctance to floss is a tangible entity. I’m sure parents all over the world are familiar with the petulant “Awww… do I have to?” which precedes any onerous personal hygiene-related task, and when it comes to flossing, it appears it is a habit we don’t grow out of.

In my experience, patients will dutifully listen to my explanation and watch my demonstration of flossing, get some from the reception desk, go home and try to floss themselves…for a day or two. The real keenie beanies will floss up to a month, and yes, there are a pleasing number of patients who do actually floss on a daily basis. But they are the minority.

Do I need to floss my teeth

What do you mean?

So let’s break this down.

Let’s assume that when we say ‘flossing’, we mean ‘flossing in addition to effective toothbrushing’, because unless you’ve got something stuck in between your teeth, you’re unlikely to just floss.

Let’s also be a bit more specific. The term ‘flossing’ is generally used for expediency when we should actually use the term ‘interdental cleaning’, but ‘interdental cleaning’ is a bit of a mouthful and ‘a bit of a mouthful’ is a really bad pun when the subject is dental related.

Interdental cleaning encompasses all methods commonly and advisedly used for cleaning in between your teeth. I say ‘advisedly’ because I can remember my Dad using the chewed end of a matchstick to clear out food debris following the butterfest that was ‘Corn of the Cob night’. This is not something, as a dental professional, I would advise you to do! Nor would I advise you use those razor-sharp ‘toothpicks’ one can find in some restaurants. The common methods we’d advise are:

  • Flossing (obviously, but to include tape and ‘superfloss’)
  • Interdental brushes
  • Interdental Cleaning Sticks (either made of wood and specially made for the task (i.e. not matchsticks!) or made of rubber or elastomeric material)
  • Oral irrigators (aka Power flossers)

So now the question is “Do I need to clean interdentally?”.

Smiling flosser


Before we answer that question, let’s look at what’s in it for the patient. Yes, if you clean interdentally regularly you will avoid a bollocking from the dentist or hygienist, and you will also earn huge smug points whenever the subject comes up in conversation. But is that all there is to it? Surely there must also be some health benefit?

Okay, so now let’s look at the potential benefits. Essentially, we use interdental cleaning to prevent gum disease and tooth decay. Ridding yourself of halitosis is another potential benefit, but way outside the scope of this blog.

With gum disease, there are two main types: Gingivitis, where the gums bleed readily, but the sockets aren’t affected, and Periodontitis, where the tooth socket is affected and which can lead to eventual tooth loss. For the purposes of this article, I will refer to gingivitis as ‘bleeding gums’ and periodontitis as ‘gum disease’, knowing full well that the distinction isn’t an accurate one.

As far as interdental cleaning and tooth decay is concerned, in this article we are only interested in preventing decay in between our teeth, assuming that our toothbrushing technique will prevent decay on the areas which it can reach.

So now the question becomes “Do I need to clean interdentally to prevent gum disease and tooth decay?”.

Okay, we’re getting somewhere. Let’s look at every permutation of that question:

  • Do I need to use floss, interdental brushes, interdental cleaning sticks or oral irrigation to prevent bleeding gums?
  • Do I need to use floss, interdental brushes, interdental cleaning sticks or oral irrigation to prevent gum disease?
  • Do I need to use floss, interdental brushes, interdental cleaning sticks or oral irrigation to prevent tooth decay?

Show me the facts, man.

So, effectively twelve questions to answer. The best place to get evidence to answer questions of a healthcare-related matter is the Cochrane Library. This organisation critically appraises the thousands of scientific articles which are written every day and determines whether there is any strong evidence to support various theories.

For the answers to the above questions, I shall be looking at the review article written by Helen Worthington and her colleagues and published in April 2019**.

Just tell me if I need to floss, will ya?

So let’s take a deep breath and carry on:

As Hippocrates, the 'Father of Medicine' once said; “First, do no harm”, and I’m sure you’ll all be relieved to know that the review found no evidence that any of the methods used for interdental cleaning caused harm (or adverse events to use the proper lingo).

From there it goes downhill a bit, sadly.

The results came with a low or very low level of certainty. This means that although in some cases they were able to get statistically significant results, they couldn’t be sure that the results were due to, for example, flossing or another factor such as simply telling the patient they are taking part in a trial. They were also unable to say whether the results would have any clinical benefit.

So let’s look at our questions:

Do I need to use floss, interdental brushes, interdental cleaning sticks or oral irrigation to prevent bleeding gums?

There were plenty of studies about bleeding gums, but unfortunately, the studies were quite short in length (one, three or six months), meaning the long-term effects are unknown.

There was some evidence that floss reduced bleeding gums, but not plaque (the sticky substance covering unclean teeth that is implicated in causing tooth decay and gum disease).

Interdental brushes may reduce plaque and bleeding gums in the short term.

Wooden cleaning sticks reduced bleeding gums, but not plaque, whereas rubber or elastomeric interdental cleaning sticks reduced plaque, but not bleeding gums in the short term. The trials that showed this were very small.

Oral irrigation may reduce bleeding gums in the short term, but no evidence that it did so in the medium term. There was no evidence that oral irrigation had an effect on plaque over and above that obtained by toothbrushing alone.

Interdental brushes may be better at reducing bleeding gums than flossing in the short to medium term.

Oral irrigation may be better than flossing at reducing bleeding gums in the short term.

There was no evidence that interdental cleaning sticks were any better or worse than flossing or interdental brushes.

Do I need to use floss, interdental brushes, interdental cleaning sticks or oral irrigation to prevent gum disease?

There were very few studies conducted into the effects of interdental cleaning on gum disease. Those that were undertaken showed no significant difference in pocket depth (a measure of how advanced the gum disease is).

Do I need to use floss, interdental brushes, interdental cleaning sticks or oral irrigation to prevent tooth decay?

No studies were undertaken to research the effects of interdental cleaning on tooth decay. None. Not one, zilch, nada. Sorry.


“Okay,” I hear you ask, getting a bit fed up now, “so do I need to floss or not?”

“Well, let’s look at what constitutes ‘scientific evidence’”, I say, desperately stalling for time.

It is very difficult to get good evidence for a trial such as one based on the effects of flossing, as merely telling someone they are taking part in a trail is enough to influence their habits. In addition, the type of person likely to be willing to enter a trial about oral hygiene is likely to have good oral hygiene already. Furthermore, it costs a lot of money to study a large group of people for even six months, and after that, you will get a large drop off in patients as they move away or get bored with the trial etc. So long term trials are difficult to achieve.

Two doctors once did a tongue in cheek article*** about how difficult it is to get good evidence. They pointed out that there is actually no strong scientific evidence to support the use of parachutes when jumping from an aeroplane. You can get the article here.

So if the evidence doesn’t support the use of flossing, why do dentists and hygienists keep banging on about it?

Anecdotal evidence, or professional experience, is actually one of the lowest levels of evidence, yet any dentist or hygienist will advise you that the people with the cleanest mouths have the fewest problems. There is no doubt about that, but very little ‘scientific evidence’ to support it.

My own opinion (a very very low, almost worthless level of evidence****) is that flossing is very difficult to do effectively every day, and that interdental brushes are (slightly) more effective and much easier to use. Interdental cleaning sticks are slightly less effective than brushes, and harder to come by. Water flossers certainly encourage and motivate patients, and are effective against bleeding gums, even if the evidence suggests this is only in the short term.

I’m afraid on this one, you’re just going to have to trust the dental profession. Yes, you do need to clean in between your teeth, but you don’t necessarily need to floss.


Interdental cleaning won’t do you any harm, and may even encourage better motivation towards oral hygiene overall.

There is no strong scientific evidence to support the theory that interdental cleaning prevents gum disease or tooth decay, but:

There is no strong scientific evidence to support the use of parachutes, either.


So there you have it. Cleared that one up, didn't I?



*What's in it for me?

**Worthington  HV, MacDonald  L, Poklepovic Pericic  T, Sambunjak  D, Johnson  TM, Imai  P, Clarkson  JE. Home use of interdental cleaning devices, in addition to toothbrushing, for preventing and controlling periodontal diseases and dental caries. Cochrane Database of Systematic Reviews 2019, Issue 4. Art. No.: CD012018. DOI: 10.1002/14651858.CD012018.pub2.

***Smith GC, Pell JP. Parachute use to prevent death and major trauma related to gravitational challenge: a systematic review of randomised controlled trials. BMJ. 2003;327(7429):1459–1461. doi:10.1136/bmj.327.7429.1459 

**** If you think 26 years in clinical practice, hundreds of hours post-graduate training per year and two degrees in dentistry is worthless.