Looking for a Christmas subject, I came across this claim: 'Dirty teeth give you pneumonia.' Not your idea of Christmas spirit? Bear with me. What happens most often at this time of year? Parties? Parties? More parties? And in between the office end-of-year cocktails, Christmas dinners with business associates, get-togethers with old friends, Christmas lunches and Christmas drinks, what else do you do? Run. Not in the healthy, pounding-the-pavement-sense. You run from meetings to forays into the food shopping jungle to even more frightening dashes into the Christmas gifts maze (or desert, when it comes to people for whom there's nothing suitable). And in between partying and running, do you do much else? If you're lucky, you might be averaging four hours' sleep a night. Yes, that's what I'm getting at. Most of us are over-fed and over-lubricated (in the alcoholic sense, at least), but desperately short of sleep. And while most of us recognise the obvious signs that the sleep meter is pointing to empty - irritability, poor memory, headaches, chronic exhaustion - few people spare a thought for their long-suffering teeth. But if you're out all day and night, chances are you're not clearing the gunk off your teeth with a thorough floss and brush regularly. And if you're drinking a lot of alcohol, eating a tonne of sugar-laden Christmas goodies and keeping your eyes open with extra doses of coffee, you're loading your teeth with the kind of sugar that bacteria love. And you're keeping your mouth relatively dry, so saliva and other fluids don't clear the bacteria away. This is where the dirty teeth and pneumonia issue starts to sound like a Christmas story. Now, this research wasn't done on the party set (unless things have changed drastically in nursing homes). What the researchers did was study the kind of bacteria found in the tooth plaque of elderly people living in homes. I won't ruin your breakfast describing exactly how they did this. All you need to know is that the plaque on elderly patients' teeth was sampled and sent off for bacterial culturing. If they later developed pneumonia, as often happens to the old who are confined to bed, the bacteria in the lung fluid was compared with the bacteria grown from the patient's tooth plaque. Sure enough, the 14 patients who got pneumonia had bacteria in the lungs matching the bacteria grown from their teeth. In other words, the bacteria lurking in your teeth are doing more than giving you caries and keeping your dentist in business. They're waiting for a chance to find a bigger, more comfortable home - in your lungs. If you get so tired and run down that your normally effective immune system lets them get a toe-hold in your lungs, they can set up a metropolis down there. Why, you might ask, did anyone even think of doing this tooth plaque study? Because there's increasing evidence that your teeth make a great base camp for bacteria looking for a better life. Under the right conditions, they can find their way into your heart, your blood stream, your kidneys and cause havoc. There's even been some research associating plaque bacteria with premature births. So, what should we do? Floss every five minutes? Brush with antibiotics? Probably not. Eliminating all the bacteria in your mouth and teeth would bring a whole set of new problems. Many of the allergic diseases, especially asthma, are now being linked with excessive hygiene. But if you've let things slip in the mouth-hygiene department and aren't getting enough sleep, you're a sitter for serious illness. So, get out there and have fun - but just before you collapse in a heap somewhere at least swig a strong mouthwash (of the dental variety) if you can't muster the strength to floss or scrub away the night's excesses with a good brushing.