Periodontal refers to the tissues around the teeth, is an inseparable part of the teeth, by the periodontal membrane, osteoid, alveolar bone, and gums composed of four parts. 1. Periodontal membrane: Periodontal membrane, also known as periodontal ligament or periodontal space, is composed of dense connective tissue, one end connects the alveolar bone, one end connects the bone, plays a role in fixing the teeth. 2. Osteoid: Osteoid is a laminated structure on the surface of the tooth root. It plays the role of repairing the damage of the root surface, combining periodontal and dental tissues. 3. Alveolar bone: Alveolar bone is the bone that surrounds and supports the roots of the teeth in the upper and lower jaws, and is closely connected to the bone through the periodontium, and the health of the alveolar bone is related to the health of the oral cavity. 4. Gums: Gums are the reddish soft tissue structures close to the necks of the teeth and the adjacent alveolar bone, which play a solid, protective and aesthetic role. If periodontal problems occur, there may be tooth pain, loose teeth, red and swollen gums, patients are advised to go to the hospital in a timely manner.