ROCHDALE, England, May 2 — "I snapped it out myself," said William Kelly, 43, describing his most recent dental procedure, the autoextraction of one of his upper teeth. Now it is a jagged black stump, and the pain gnawing at Mr. Kelly's mouth has transferred itself to a different tooth, mottled and rickety, on the other side of his mouth. "I'm in the middle of pulling that one out, too," he said. It is easy to be mean about British teeth. Mike Myers's mouth is a joke in itself in the "Austin Powers" movies. In a "Simpsons" episode, dentalphobic children...