Periodontal disease, also known as gum disease, is a set of inflammatory conditions affecting the tissues surrounding the teeth. In its early stage, called gingivitis, the gums become swollen and red and may bleed. It is considered the main cause of tooth loss for adults worldwide. In its more serious form, called periodontitis, the gums can pull away from the tooth, bone can be lost, and the teeth may loosen or fall out. Halitosis (bad breath) may also occur.

Periodontal disease typically arises from the development of plaque biofilm, which harbors harmful bacteria such as Porphyromonas gingivalis and Treponema denticola. These bacteria infect the gum tissue surrounding the teeth, leading to inflammation and, if left untreated, progressive damage to the teeth and gum tissue. Recent meta-analysis have shown that the composition of the oral microbiota and its response to periodontal disease differ between men and women. These differences are particularly notable in the advanced stages of periodontitis, suggesting that sex-specific factors may influence susceptibility and progression. Factors that increase the risk of disease include smoking, diabetes, HIV/AIDS, family history, high levels of homocysteine in the blood and certain medications. Diagnosis is by inspecting the gum tissue around the teeth both visually and with a probe and X-rays looking for bone loss around the teeth.

Treatment involves good oral hygiene and regular professional teeth cleaning. Recommended oral hygiene include daily brushing and flossing. In certain cases antibiotics or dental surgery may be recommended. Clinical investigations demonstrate that quitting smoking and making dietary changes enhance periodontal health. Globally, 538 million people were estimated to be affected in 2015 and has been known to affect 10–15% of the population generally. In the United States, nearly half of those over the age of 30 are affected to some degree and about 70% of those over 65 have the condition. Males are affected more often than females.

In the early stages, periodontitis has very few symptoms, and in many individuals, the disease has progressed significantly before they seek treatment.

Symptoms may include:

Gingival inflammation and bone destruction are largely painless. Hence, people may wrongly assume painless bleeding after teeth cleaning is insignificant, although this may be a symptom of progressing periodontitis in that person.

Periodontitis has been linked to increased inflammation in the body, such as indicated by raised levels of C-reactive protein and interleukin-6. It is associated with an increased risk of stroke, myocardial infarction, atherosclerosis and hypertension. It is also linked in those over 60 years of age to impairments in delayed memory and calculation abilities. Individuals with impaired fasting glucose and diabetes mellitus have a higher degrees of periodontal inflammation and often have difficulties with balancing their blood glucose level, owing to the constant systemic inflammatory state caused by the periodontal inflammation. Although no causal association was proven, there is an association between chronic periodontitis and erectile dysfunction, inflammatory bowel disease, and heart disease.

A positive correlation between raised levels of glucose within the blood and the onset or progression of periodontal disease has been shown in the current literature.