Because the gums are often not easily distinguishable from the teeth, gum recession can occur as well as tooth recession in daily life. Gum recession is usually the result of periodontitis. Periodontitis is the further development of gingivitis, and when the disease enters periodontitis, the periodontal membrane around the tooth tip dissolves and resorbs, causing the alveolar bone to resorb as well. Periodontitis can be treated with subgingival scraping to relieve the inflammation and stop the development of shrunken gums. In contrast, tooth atrophy is usually due to a long period of bite trauma resulting in the thinning of the enamel on the tooth surface, even to the dentin. In this case, the crown height decreases and the symptoms of atrophy are manifested.