While it might be true that no man is an island, it seems that his teeth are. According to researchers studying the bacteria that cause gum disease, your pearly whites have more in common with a tropical archipelago than you think.

Clara Long of Stanford Medical School in California (the spritual home of the perfect smile) have been applying the techniques of biogeography – a discipline that more commonly deals with patterns of species distribution on scattered islands of terrain – to work out which bacteria live where in your mouth.

The picture is surprisingly complex. Using DNA-sampling methods, Long and her colleagues estimate that more than 700 different bacterial species make their home in your mouth. And each tooth does indeed seem to be an island – patterns of species colonization are strikingly different between neighbouring teeth. In fact, if one of your teeth succumbs to gum disease (which affects up to 85% of US adults) or the more severe periodontitis, the next tooth to be infected is likely to be one opposite, not the one adjacent.

The emerging picture of the intricate ecosystem inside your mouth suggests that the main benefit of brushing is to prevent the colonizers at the top of the food chain from gaining a foothold – although many bacteria that live in your mouth may actually prevent the disease-causing ones from getting a look-in. So it seems that the cartoon diagrams beloved of toothpaste adverts are lying to us, and that bacteria are an unavoidable ever-present in our mouths. After all, you swallow around 100 million of them every day.

Perhaps most strangely of all, the sacred act of flossing may inadvertently spread infection around the entire body, by causing tiny cuts in the gums that allow bacteria into the bloodstream. This has been linked to a range of medical conditions from cardiovascular infections to early induction of labour. On balance though, as your dentist will tell you, that’s not an excuse not to floss…