The mechanisms by which health is preserved in the face of potential disease, that is the defense mechanisms, can be roughly divided into innate defense mechanisms and acquired defense mechanisms. The innate immunity acts as a first line of defense against infections, eliminating most potential pathogens before they establish an overt infection. This defense mechanism is present since birth and is the resistance to infection, which an individual possesses by virtue of his genetic and constitutional make up. If the innate defense mechanism is unsuccessful, the adaptive immune system is activated and produces a specific reaction to each infectious agent. The adaptive immune system also remembers the infectious agent and can prevent it from causing disease later.The gingival tissue is constantly subjected to mechanical and bacterial aggressions. The saliva, epithelial surface and the gingival crevicular fluid provide resistance to these actions.
