 Half of the adult British population suffers from a disease which we've all but forgotten about. This is possibly because this disease, a bit like England at this year's Football World Cup, is not really considered a threat. But this disease can destroy your bones, has no fully effective cure and can reduce the quality of your life. I'm talking about gum disease, a disease we associate with bleeding and swollen gums, but that can cause bad breath and result in tooth loss. On a microscopic scale, gum disease is a fascinating battle between an unbeatable bacterial army and our body's defensive forces. Gum disease is caused by a colony of bacteria we know as dental plaque. But all the external surfaces of our body are covered in bacteria, so why are they a problem on our gum line? Firstly, you don't find teeth anywhere else in the body, so we have a unique environment. Secondly, the mouth is a great place for bacteria to live. It's protected, warm and full of nutrients. This means that bacteria can grow so quickly that within one day they are visible to the naked eye. So what weapons do we have against this threat? Our body's first lines of defence consist of saliva which acts as an antibacterial wash and the barrier formed by intact gum tissue keeping bacteria on the outside of our body. However, bacteria favour growing in the area between our teeth and gums, where this barrier is only thin and weak. This threat invasion activates our body's second line of defence called inflammation. Inflammation is the almost instantaneous response we recognise as swelling, bleeding and pain after cutting ourselves or being stung, and it's there to help wounds heal and to kill bacteria. Unfortunately, because of the sheer volume of bacteria in our mouth, we simply do not have the energy or resources required to kill them all. All we can hope to do is keep them on the outside of our body. And this is where the damage really occurs because while inflammation is very powerful, it's nonspecific, so it can kill invading bacteria but will also damage our own cells. A kind of friendly fire situation. Even worse, in a stalemate like this when inflammation remains switched on, it spreads almost like a cancer throughout the gums and can even damage and dissolve the jaw bones. At this point in time, gum disease can be really difficult to treat, but thankfully, even before recorded history, we'll be using our brains to solve the problem. And it appears that the first recorded use of one of these was during the Tang dynasty in China well over a thousand years ago. Next time you brush your teeth, just remember that with the humble toothbrush in your arsenal, not only are you winning the daily battle against plaque bacteria, but you're preventing the seemingly unbeatable war against gum disease too.