All surfaces of the oral cavity are covered by bacteria that will depend on the environmental conditions for each moment.
On the one hand, there are aerobic bacteria, which need oxygen to survive and multiply. On the other hand, anaerobic bacteria, which thrive in the absence of oxygen, develop mostly at night while we sleep.
In the mouth of a healthy person there are mostly bacteria from the genera Streptococcus, Actinomyces and Fusobacterium. The bacteria responsible for plaque are usually specifically Streptococcus mutans.
As long as the growth of these types of bacteria is controlled with good oral hygiene, proper nutrition, and the protective action of the immune system in the human body itself, their presence does not have to be harmful.
