The cause of dental calculus is plaque or soft tartar. Tartar, also known as tartar, is a kind of plaque or soft tartar deposited around the teeth, which is mineralized or unmineralized. Saliva contains inorganic salts such as calcium salts, and the plaque or soft tartar can calcify and is not easily removed by brushing or rinsing. Tartar is divided into supragingival tartar and subgingival tartar. Supragingival tartar is visible to the naked eye, and the gum margin may appear red and bleeding, and needs to be removed by ultrasonic scaling. Subgingival tartar is attached to the root surface of the teeth and is not easily visible, but it is very damaging to the periodontium and can easily cause damage to the alveolar bone, resulting in loose and lost teeth. The composition of tartar includes organic components, inorganic components and water, but also shedding epithelial cells and various microorganisms. There is a relationship between tartar and inflammation of the gums. The pathogenic effect of tartar is mainly plaque on the tooth surface, which can irritate the gums to form gingivitis. Tartar has many rough spaces that can attract a large number of bacteria, and tartar is attached to the tooth surface and cannot be removed by brushing. The key to tartar prevention is to prevent the buildup of plaque. So unmineralized plaque or soft tartar is the etiology of tartar formation.