How many bacteria are there in human mouth?
500 to 1000 different types
Believe it or not, adult mouths may contain 500 to 1,000 different types of bacteria. Keep in mind that they form the human flora and oral microbiology. Needless to say, about 100 to 200 species may live in them at any given time. It is important to know the fact that the persons who care for their teeth and have a relatively clean mouth have 1,000 to 100,000 bacteria living on each tooth surface. On the contrary, those that do not have a clean mouth have between 100 million and 1 billion bacteria on each tooth. This is terrible.