Causes

Periodontal disease is marked by bacterial overgrowth. However, a persistent immune response to chronic infections in the mouth is now believed to play a major role in gum destruction.

Bacterial Culprits

In the healthy mouth, more than 350 species of microorganisms have been found. Periodontal infections are linked to fewer than 5% of these species. Healthy and disease-causing bacteria can generally be grouped into two categories:

• The harmless or helpful bacteria are usually known as gram positive aerobic bacteria.
• In periodontal disease, the bacterial balance shifts over to gram negative anaerobic bacteria. Inflammatory disease and injury cannot develop without these bacteria.

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Following are some of the bacteria most implicated in periodontal disease and bone loss:

• Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis. These two bacteria appear to be particularly likely to cause aggressive periodontal disease. In one study, both P. gingivalis and A. actinomycetemcomitans, along with multiple deep pockets in the gum, were associated with resistance to standard treatments for gum disease. In another study, P. gingivalis doubled the risk for serious gum disease. Particularly virulent strains of this bacteria may be responsible for periodontal disease. A 2001 study suggests that the P. gingivalis produces enzymes, such as one called arginine-specific cysteine proteinase, which may be the specific destructive factors that disrupt the immune system and lead to subsequent periodontal connective tissue destruction.
• Bacteroides forsythus is also strongly linked to periodontal disease.
• Other bacteria associated with periodontal disease are Treponema denticola, T. socranskii and P. intermedia. These bacteria, together with P. gingivalis, are frequently are present at the same sites, and are associated with deep periodontal pockets.