The root of grade 6 20 12-04-26 teeth is not directly on the alveolar bone (gum), but there is a thick layer of gum tissue between them [1], which is called "periodontal tissue" in modern stomatology (perhaps the inner gum will be more vivid). Therefore, the combination of teeth and alveolar bone is actually a kind of joint relationship, which belongs to the micro-motion joint in the human body (the range of motion is small), so even strong and healthy teeth will feel slightly active when touched by hand. The alveolar bone is basically supported by the surrounding gingival tissue. When the gums age and shrink, the ability to deliver nutrition to the alveolar bone decreases day by day, and the alveolar bone shrinks and shortens, which is called "bone absorption phenomenon" in stomatology. Gingival atrophy causes the wrapping strength of this "fretting joint" to decrease, and the teeth begin to loosen. At the same time, the alveolar bone is absorbed, which makes the tooth root shallower and the teeth longer. With more and more bone absorption, teeth naturally fall off. On the other hand, after gingival atrophy, the root can no longer be tightly wrapped as before, which leads to the exposure of periodontal tissue (inner gum), and various bacteria (especially anaerobic bacteria) and dental calculus in the mouth directly invade the periodontal tissue, causing periodontitis. Periodontitis will in turn aggravate gingival atrophy, accelerate alveolar bone absorption, and form a vicious circle. As a result, it not only damages gums and teeth, but also threatens health. At present, stomatology believes that gingival atrophy is irreversible, so periodontitis cannot be cured, so it will be listed as the third biggest killer threatening human health by the World Health Organization. In short, root exposure after gingival atrophy has a great relationship with alveolar bone absorption!