Editing Periodontal disease (section)

==Mechanism==
As dental plaque or biofilm accumulates on the teeth near and below the gums there is some [[dysbiosis]] of the normal [[oral microbiome]].<ref name=Kinane2017rev>{{cite journal | vauthors = Kinane DF, Stathopoulou PG, Papapanou PN | title = Periodontal diseases | journal = Nature Reviews. Disease Primers | volume = 3 | pages = 17038 | date = June 2017 | pmid = 28805207 | doi = 10.1038/nrdp.2017.38 | s2cid = 28018694 }}</ref> As of 2017 it was not certain what species were most responsible for causing harm, but [[gram-negative]] anaerobic bacteria, spirochetes, and viruses have been suggested; in individual people it is sometimes clear that one or more species is driving the disease.<ref name=Kinane2017rev/> Research in 2004 indicated three gram negative anaerobic species: ''[[Aggregatibacter actinomycetemcomitans]]'', ''[[Porphyromonas gingivalis]]'', ''[[Bacteroides forsythus]]'' and ''[[Eikenella corrodens]]''.<ref name=Preshaw04/>

Plaque may be soft and uncalcified, hard and calcified, or both; for plaques that are on teeth the calcium comes from saliva; for plaques below the gumline, it comes from blood via [[Transudate|oozing]] of inflamed gums.<ref name=Kinane2017rev/>

The damage to teeth and gums comes from the immune system as it attempts to destroy the microbes that are disrupting the normal symbiosis between the oral tissues and the oral microbe community. As in other tissues, [[Langerhans cells]] in the [[epithelium]] take up [[antigens]] from the microbes, and present them to the immune system, leading to movement of [[white blood cell]]s into the affected tissues. This process in turn activates [[osteoclasts]] which begin to destroy bone, and it activates [[matrix metalloproteinases]] that destroy ligaments.<ref name=Kinane2017rev/> So, in summary, it is bacteria which initiates the disease, but key destructive events are brought about by the exaggerated response from the host's immune system.<ref name=Preshaw04/>