I am selling this because I no longer use it. Invisible fine scratches on the surface of the teeth can cause plaque and stains to adhere. The nano-particle medicinal hydroxyapatite contained in Apaguard Renamel repairs damaged tooth surfaces and replenishes minerals in the teeth. It makes it difficult for plaque and stains to adhere, and prevents tooth decay. Feature 1: Adsorbs and removes plaque Nano-particle medicinal hydroxyapatite has the property of adsorbing mutans bacteria, which are the source of plaque. Feature 2: Fills microscopic scratches Nano-particle medicinal hydroxyapatite is ultra-fine! It replenishes hydroxyapatite, the main component of teeth, at the nano level. By filling microscopic scratches, the teeth become smooth, making it difficult for plaque and stains to adhere. Feature 3: Remineralizes early-stage cavities Nano-particle medicinal hydroxyapatite replenishes the minerals that have dissolved from the enamel and remineralizes it.