A common, severe gum infection affecting the tissues and bone supporting the teeth (periodontium). Uncommon in children and more common in adolescents and adults.

Develops when gingivitis is left untreated and infection and inflammation spreads into the periodontium. In some cases, a tooth abscess may develop due to bacterial buildup (plaque). If the condition is ignored, the inflammation leads to further damage of periodontium and may cause tooth loss.

Periodontitis is usually preventable and typically results from poor oral hygiene. Other risk factors include gingivitis, family history of periodontitis, tobacco use, diabetes, older age, weakened immune system, substance abuse, and poor nutrition.
 
Symptoms depend on severity of disease but may include swollen, tender, and/or bleeding gums, receding gums, gums that are red or purple, halitosis, and loose teeth. Complications include tooth loss, heart disease, stroke, diabetes complications, rheumatoid arthritis, and asthma.

The primary goal of treatment is to minimize inflammation, clean the "pockets" in the gums, prevent damage to surrounding bone, and address any underlying causes of disease. In less advanced cases, less invasive procedures such as scaling, root planing, and antibiotics may be used for treatment. In more severe cases, surgical treatments such as flap surgery, soft tissue or bone grafting, guided tissue regeneration, and enamel matrix derivate application are possible treatment options.

Prognosis is good once periodontitis is treated and routine good oral hygiene is maintained.