Most people hope they will never have to visit the arse dentist - in a recent survey, up to 40% of British people denied that they even exist. But for a significant proportion of older people, it is an inevitability.
Teeth can protude from the anus when the roots of wisdom teeth become so long that they reach down to the rectal area. Some people also grow them naturally, as vestigial remnants of our prehistoric ancestors who used to wallow in the seas and eat fish who swam up their arses.
With people living longer than ever, the arse dentist has become a common sight on high streets throughout the UK. Often arse dentists share their premises with normal dentists, with their special upside-down chair being kept in a separate room.
Anal teeth - or sub-colonic molars as they are technically known - cannot be extracted but should be checked regularly. The National Association of Rectal Dentists (NARD) warn that people should clean their brown eye teeth daily. Spokesman Wade O'Penn explained, "Some people like to eat with their anus, which is fine. So is chewing gum. In fact it can be excellent exercise for the buttocks. However, it can lead to a dangerous build-up of plaque. You must remember to brush your arse twice a day. And remember to use a separate toothbrush from your mouth."
Another difference between teeth and arse teeth is that the arse teeth have to cope with a regular flow of faecal matter - leading to the curious elderly problem of toothmarks in the stool which is often misdiagnosed as a mental issue. However, arse dentists claim that contact with faeces does not affect the teeth adversely.
Barry Prolapse, 56, is due for his regular checkup at his arse dentist. He has previously had a filling on one of his arse teeth and has been warned by the dentist that he may need another if any more cavities are found up there.
He said, "I'm getting fed up to the back teeth with all these damn trips to the arse dentist. They never fall out and you can't get rid of them. There's no chance of a visit from the arse tooth fairy."
He continued, "Not all of us can have a nice pearly white arse smile like they do in Hollywood. One dentist said that two of my arse teeth have begun to interlock dangerously, and I might even need to wear braces!"