A biologist with a history of tooth decay invents a symbiotic microbe which lives in the human mouth and feeds by cleaning our teeth. It secreted calcium, which is poisonous to it, controlling its growth and preventing it from eating the teeth themselves. So this guy, he wants to spread the thing to the world, but it'd never fly, FDA and human squeamishness and all, so he becomes a party animal. He throws wild partys at the lab, kisses female grad students, where's, babies. He backwashes in sodas left on tables. He bums drags of cigarettes. He grants humanity eternally clean and healthy teeth but dies of a terrible cocktail of STDs.