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When two people kiss, they exchange between 10 million and 1 billion bacteria.


Oral ecology refers to the organisms that live in a mouth. Bacteria in biofilm were first detected under the microscopes of Antony van Leeuwenhoek in the 17th century. Various bacteria and saliva are two of the major components in oral microbiology, having the capability to be harmful, but also performing beneficial and necessary roles in the immune system. Proper oral hygiene aims to control the harmful effects and prevent disease transmission.

Bacteria were first detected under the microscopes of Antony van Leeuwenhoek in the 17th century. Leeuwenhoek, a Dutch scientist, performed many experiments testing and observing bacteria. He observed plaque on his own teeth—

“a little white matter” as he called it.Under microscopes he saw “that in the said matter there were many very little living animalcules, very prettily a-moving,”

which was the first sighting of oral bacteria as we know it.Leeuwenhoek tested the mouths of others, as well as his own. Two men that he tested had never cleaned their teeth in their lives and Leeuwenhoek found “an unbelievably great company of living animalcules…in such enormous numbers, that all the water…seemed to be alive.” Thus Leeuwenhoek discovered oral bacteria or “animalcules,” the name he gave bacteria in general.

Later studies have shown that he actually saw mats of bacteria, what we know today as biofilms. Biofilms are communities of bacteria, or micro-organisms, attached to surfaces in the body. Oral biofilms are more commonly referred to as plaque. Biofilms form almost everywhere bacteria are. In the mouth, they naturally form on any stationary surface, namely teeth, gums, and the tongue. Leeuwenhoek made important findings of bacteria with his first observation and analysis of dental plaque, and since then much more has been discovered about the mouth and its ecology.

The human mouth contains around 500 to 1,000 different types of Bacteria with various functions as part of the human flora and oral microbiology. About 100 to 200 species may live in them at any given time. Individuals that practice oral hygiene have 1,000 to 100,000 bacteria living on each tooth surface, while less clean mouths can have between 100 million and 1 billion bacteria on each tooth.While some of the bacteria in our mouths are harmful and can cause serious illness, much of our oral bacteria are actually beneficial in preventing disease. Streptococci make up a large part of oral bacteria.