Periodontal disease, also known as gum disease, is an infection of the tissues that surround and support your teeth. It typically starts with the buildup of plaque – a sticky film of bacteria – along the gumline. Without proper oral hygiene, plaque can harden into tartar, leading to inflammation of the gums (gingivitis). If left untreated, gingivitis can progress to periodontitis, causing irreversible damage to the gums and bone that support the teeth.