Floss is not the only way to get rid of the biofilm between teeth. The characteristics of your teeth – crowded or widely spaced, for instance – will determine what will work best, a small brush or a thin piece of floss. For those who have gum or teeth problems, interdental cleaning is an opportunity to go all-out. “Lots of our patients use a wide variety of interdental cleaning devices, so they have maybe five or six different brushes of different sizes, floss and other brushes,” says Hirschfeld. The time spent flossing should be considered part of your two-minute clean, she adds, and there’s no need to do it more than once a day.
This is despite one review of randomised controlled trials (RCTs) in 2011 claiming there was only “weak, very unreliable evidence which suggests that flossing plus toothbrushing may be associated with a small reduction in plaque at one or three months”, and most studies had methodological flaws. However, that review was later withdrawn, after objections that the “absence of evidence is not the evidence of absence”. A later, updated version found that flossing was significantly better than brushing alone at reducing gingivitis (superficial gum disease, which can lead later to deep gum disease, or periodontitis), though the evidence that it reduced plaque was still “weak” and “very unreliable”.
“It is really hard to conduct these types of studies,” says Hirschfeld. It’s difficult to get a large enough cohort, reflective of the general population and not simply dental students who are easy to recruit to such studies, and to get around factors such as the unreliability of self-reporting. Another major challenge is carrying out the studies long enough to see how the incidence of teeth and gum problems is altered, which can take decades. “That is hard, if not impossible, to do. That’s why the evidence is weak.”
What kind of toothpaste is best?
While there is a plethora of different toothpastes, from cavity-prevention to whitening to sensitivity-reduction, expensive brands aren’t necessary to do the essentials, Hirschfeld and Carter agree.
“I’ve looked at the ingredient list of some of the really cheap toothpastes that I’ve seen, as cheap as 40p on occasion, and I don’t see anything wrong with them,” says Hirschfeld.
Of the long list of ingredients on the back of an average packet of toothpaste, there is one ingredient in particular to look out for: “Fluoride content,” says Hirschfeld. “That is definitely the key factor.” It should be around at least 1,350 parts per million (ppm) for adults, and 1,000 ppm for children to protect the enamel from acids.
Tooth enamel is the hardest tissue in the human body, and one of the hardest found in nature. “Almost as hard as diamond,” notes Hirschfeld. It is mostly made up of a mineral called hydroxyapatite (a kind of calcium phosphate) arranged in a complex crystalline structure, which varies in different forms and arrangements throughout the tooth to increase hardness and durability.
But despite its resilience to mechanical force, enamel is easily dissolved in acid. The microbes present in the biofilm release lactic acid as a by-product from digesting the sugars and carbohydrates that can become trapped between our teeth. This lactic acid gradually leaches calcium and phosphate from the enamel, which eventually begins to crumble and forms a cavity.
Compounds naturally present in the saliva can go some way to replacing the lost minerals. In particular, if fluoride is present (as it naturally is in soils and water in many parts of the world), then the enamel reforms as fluorapatite, which is more resistant to acids than hydroxyapatite. Spitting out toothpaste when you’re finished but refraining from rinsing helps the fluoride to hang around the teeth longer, for additional protection.
“Since fluorides have been introduced into toothpaste, the incidence of cavities has gone down everywhere where fluoridated toothpaste is used,” says Hirschfeld.
However, some fashionable ingredients should be treated with caution. Charcoal, which has been used to clean teeth for millennia and has become increasingly popular in commercial toothpastes, has less research to back it up. There is little evidence charcoal whitens teeth, and it may increase the risk of tooth erosion and other problems. Claims regarding antibacterial, antifungal and antiviral properties of charcoal toothpastes cannot be substantiated, according to one review, concluding dentists should “advise their patients to be cautious when using charcoal and charcoal-based [dental products] with unproven claims of efficacy and safety”.
Many charcoal toothpastes don’t contain fluoride, and therefore offer less protection from cavities. However, if someone uses a toothpaste with no added fluoride, they will still get some benefit from brushing their teeth. “They can still get the mechanical plaque removal,” says Carter. “But they’re not going to get the decay-prevention benefit, which is essentially what fluoride in toothpaste does.”
Some other popular additives in toothpaste may be less controversial. Toothpastes containing baking soda (small crystals of sodium bicarbonate) have been found to remove plaque better than those without, according to the authors of one meta-analysis, though they noted more follow-up studies were needed (the authors of that study stated that they had received funds from toothbrush and toothpaste manufacturers in the past). The same analysis found that baking-soda toothpastes may give a slight reduction in bleeding due to gingivitis.
Should you use mouthwash?
Mouthwash is less effective than teeth-brushing at removing plaque, says Carter, but when combined the two can remove a little more plaque than brushing alone. “I would say that it’s a very useful additional element, not to replace tooth brushing but as an addition.”
It can, however, be useful for treating gingivitis, according to one recent consensus statement. To be useful, it should contain at least 100ppm fluoride and be clinically proven to reduce plaque. And it is best to use it only if your gums are already bleeding, rather than as a preventative measure.