Periodontal Disease


Related Posts:

Photo of teeth with yellowing and red inflamed gums.
Redness and irritation of the gums are evidence of gingivitis.

Source: OpenStax Microbiology

OpenStax Microbiology

In addition to damage to the teeth themselves, the surrounding structures can be affected by microbes. Periodontal disease is the result of infections that lead to inflammation and tissue damage in the structures surrounding the teeth. The progression from mild to severe periodontal disease is generally reversible and preventable with good oral hygiene.

Inflammation of the gums that can lead to irritation and bleeding is called gingivitis. When plaque accumulates on the teeth, bacteria colonize the gingival space. As this space becomes increasingly blocked, the environment becomes anaerobic. This allows a wide variety of microbes to colonize, including PorphyromonasStreptococcus, and  Actinomyces. The bacterial products, which include  lipopolysaccharide (LPS),  proteases, lipoteichoic acids, and others, cause inflammation and gum damage. It is possible that methanogenic archaeans (including Methanobrevibacter oralis and other Methanobrevibacter species) also contribute to disease progression as some species have been identified in patients with periodontal disease, but this has proven difficult to study. Gingivitis is diagnosed by visual inspection, including measuring pockets in the gums, and X-rays, and is usually treated using good dental hygiene and professional dental cleaning, with antibiotics reserved for severe cases.

Over time, chronic gingivitis can develop into the more serious condition of periodontitis. When this happens, the gums recede and expose parts of the tooth below the crown. This newly exposed area is relatively unprotected, so bacteria can grow on it and spread underneath the enamel of the crown and cause cavities. Bacteria in the gingival space can also erode the cementum, which helps to hold the teeth in place. If not treated, erosion of cementum can lead to the movement or loss of teeth. The bones of the jaw can even erode if the infection spreads. This condition can be associated with bleeding and halitosis (bad breath). Cleaning and appropriate dental hygiene may be sufficient to treat periodontitis. However, in cases of severe periodontitis, an antibiotic may be given. Antibiotics may be given in pill form or applied directly to the gum (local treatment). Antibiotics given can include tetracycline, doxycycline, macrolides or β-lactams. Because periodontitis can be caused by a mix of microbes, a combination of antibiotics may be given.

Diagram of a tooth with healthy gums. The crown is the part above the gums, the root is the part below the gums. The enamel is the outer layer, inside is the dentin and inside that is the pulp which contains the root canal, nerves, and blood vessels. Below the gums is bone. Gingivitis is the first stage of periodontal disease. This is when the gums become darker red and swollen. Periodontitis the gumsrecede and the enamel begins to break. In advanced periodontitis the gums recede even further and the tooth degenerates past the enamel and into the dentin and pulp.
(a) Healthy gums hold the teeth firmly and do not bleed. (b) Gingivitis is the first stage of periodontal disease. Microbial infection causes gums to become inflamed and irritated, with occasional bleeding. (c) In periodontitis, gums recede and expose parts of the tooth normally covered. (d) In advanced periodontitis, the infection spreads to ligaments and bone tissue supporting the teeth. Tooth loss may occur, or teeth may need to be surgically removed. (credit: modification of work by “BruceBlaus”/Wikimedia Commons)


Parker, N., Schneegurt, M., Thi Tu, A.-H., Forster, B. M., & Lister, P. (n.d.). Microbiology. Houston, Texas: OpenStax. Access for free at: