For years, dentists have ordered us to floss. Is it a waste of time? Helen Rumbelow meets the woman behind a revolution

A little while ago, David Sedaris, the American humourist, took as his subject European dental care. He had, he wrote in The New Yorker, proudly told his French dentist he had been flossing every night. "Hey," she retorted, "enough with the flossing. You have better ways to spend your evenings."

To an American audience this was a cue for big laughs. Big, white, toothy laughs, from the nation that invented dental floss and went on to elevate flossing to the status of semi-religious devotion – they use nearly five million kilometres of it a year. Americans don't flagellate themselves, they attack their teeth with nylon wire until they sting and bleed. And now, increasingly, so do we.

I laughed at the Sedaris piece myself, probably even while flossing. Probably even in bed, for you do not know true intimacy until you have flossed in the presence of your loved one.

According to Clint Eastwood's former partner Sondra Locke, in her book The Good, the Bad and the Very Ugly, the Hollywood star would whisper, "Sweetie, did you floss?" as a prelude to sex.

We all know we should floss, even if we don't. The sight of a floss packet triggers a secular guilt. But what if we don't need to floss? What if the reproachful sermon of every dentist you have ever known, to floss more, floss harder, was wrong? What if we looked back on ourselves 50 years from now and laughed at our attempts to clean our teeth by wedging bits of string between them?

Well, I discovered a dentist who believes just that. My first instinct when Ellie Phillips cheerfully told me, "Oh, I haven't flossed in 20 years, and I've never taught any of my children to either," was of utter shock.

Are dentists even allowed to say this? Don't they get struck down by some flossing god? My second thought was that she was obviously a kook, not aided by the fact that her book is somewhat jauntily entitled Kiss Your Dentist Goodbye.

But it turns out that Dr Phillips was one of the first female dentists trained by Guy's Hospital in London in the 1960s. On her first day in the job in a school clinic she faced a row of 20 children with teeth to be extracted – "strained little faces looked at me with round moist eyes".

She vowed then to devote herself to preventative dentistry. Her work took her to America, where she is now based; her book is endorsed by Richard Carmona, the former Surgeon General of the United States. And its 21 pages of footnoted references to scientific studies lead to astounding conclusions: first, that flossing is useless at preventing tooth decay.

Yes, you heard that right. In all the reviews of flossing studies, no amount of flossing – daily, twice daily – has shown any reduction in your chances of tooth decay.

There was only one exception: in which schoolchildren received a professional 15-minute flossing from a hygienist five days a week for nearly two years.

But, writes Phillips in her book, despite a total lack of evidence for the preventative effect of flossing on tooth decay, "dentists have repeated the flossing mantra for 50 years".

So, I accept the challenge. I go to my hygienist. She gives my mouth, at best, six out of 10, despite my usual guilty frenzy of flossing in the weeks leading up to the visit. Will she, I manage to mumble as she scrapes gunk out of my gums, be able to tell if I stop flossing?

"Of course," she says. "Your gums will bleed and there will be plaque climbing the walls."

I tell her I will do something different, I won't tell her what, and be back in one month, the minimum amount of time Phillips says that her system takes to see results.

I stop flossing, and head straight to the supermarket to stock up. Half of the effectiveness of Phillips's system, she says, is from using mouthwash, the other half from eating xylitol, a natural type of sugar alternative that comes from birch trees.

The underlying basis of her approach, as one dentist explains in the foreword to her book (warning: gross-out alert) is to think of your mouth as a fish tank, and the teeth as the stones.

You could floss those stones night and day, but if the water remained dirty, you would be wasting your time. So the Phillips system aims to alter the chemistry of your mouth.

She uses three different mouthwashes in a specific order. If you need reassurance, look at the trial of Listerine Original (one of her favoured products), in which one group flossed daily and the other used Listerine twice daily.

After six months, the Listerine group reduced their plaque by 52pc more than the flossing group, and their gum health improved by 21pc more than the flossers (whose dental health barely differed from those who didn't floss or use mouthwash).

As for the xylitol, well, that is a revelation to me. For instance, mothers who chewed xylitol during pregnancy have children who are 70pc less likely to have tooth decay at the age of five. So this is what I do: use mouthwashes twice a day and pop a couple of xylitol sweets after every meal. It feels decidedly counterintuitive, this eating of something so super-sweet to help your teeth.

So why hasn't any dentist ever mentioned this stuff to me before? First, I ask Nigel Carter, chief executive of the British Dental Health Foundation. He has said xylitol "may be the biggest advance against cavities since fluoride".

"The dental profession is generally slow to adapt to new ideas," he said. "On xylitol, I think it's probably lack of knowledge. Any dentist should be aware of the effects of xylitol, but as a profession we do get very bogged down in the mechanical removal of plaque."

In Scandinavia, where xylitol was first championed because of the ready access to birch trees, children are regularly given free xylitol sweets in schools and nurseries.

And do they have better teeth?

"Oh yes, they tend to."

Next I talk to Aubrey Sheiham, emeritus professor of dental public health at University College London.

"Flossing is almost completely useless, it doesn't stop tooth decay," he says, adding that he has "slides of bacteria waving as the floss goes past.

"It is still useful for stopping gum disease, but you have to be meticulous – it's time-consuming."

On the other hand, he, like so many at the forefront of preventative dentistry, "would advise people to use xylitol. I have some xylitol mints in my desk drawer. If you look at the evidence it is overwhelming that xylitol works. If a child gets it a couple of times a day, they will get less decay."

By the end of the month, I go back to the hygienist. I wait, open-mouthed, for the result. She says that she cannot find a single speck of plaque on my teeth or beneath the gum line, no bleeding, inflammation, nothing.

She dramatically puts down her tools, saying there is simply no point her trying to do anything to such a perfectly clean mouth (this, needless to say, has never happened to me before).

I immediately resolve to stick with the programme, find creative new uses for my packs of floss and, what's more, begin to dole out xylitol sweets to my delighted children after meals.

Oh, and take whatever bunkum my dentist tells me about prevention with a big spoonful of sugar.

Irish Independent