exacerbate the onset, progression, and severity of periodontitis. although the majority of research has focused on type 2 diabetes, type 1 diabetes appears to have an identical effect on the risk for periodontitis. the extent of the increased risk of periodontitis is dependent on the level of glycaemic control. therefore, in well managed diabetes there seems to be a small effect of diabetes on the risk for periodontitis. however, the risk increases exponentially as glycaemic control worsens. overall, the increased risk of periodontitis in diabetics is estimated to be between two and three times higher. so far, the mechanisms underlying the link are not fully understood, but it is known to involve aspects of inflammation, immune functioning, neutrophil activity, and cytokine biology. mechanism as dental plaque or biofilm accumulates on the teeth near and below the gums there is some dysbiosis of the normal oral microbiome. 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. research in 2004 indicated three gram negative anaerobic species: aggregatibacter actinomycetemcomitans, porphyromonas gingivalis, bacteroides forsythus and eikenella corrodens. 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 oozing of inflamed gums. 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 cells into the affected tissues. this process in turn activates osteoclasts which begin to destroy bone, and it activates matrix metalloproteinases that destroy ligaments. 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. classification person with periodontitis