Periodontal disease is regarded as a chronic disease. There is a long way to go no matter one chooses to treat or maintain. The cause of periodontal disease is highly relevant to insufficient oral healthcare. If oral cleaning is insufficient for a long period, periodontal bacteria in the mouth will produce dental plaques on the tooth surface, and the dental plaques will form dental calculi, causing periodontal tissue inflammation, gingival bleeding, gingival redness and swelling. All of these will damage surrounding alveolar bones. In severe conditions, teeth will get loose or even fall out.

A “periodontal sag” is formed as the gums originally attached to the root surface are separated because of periodontal tissue inflammation, which is a favorable place to accumulate a large amount of dental bacterial membrane. Dentists will clean the bacterial membrane and calculi on the root surface of the teeth thoroughly in the periodontal sag by deep periodontal cleaning.