The tough yet thin outer layer of the tooth is composed of dental enamel, which protects teeth from the daily assault of physical and chemical wear of chewing, grinding, food and drink. Dental caries, known as cavities, are the primary cause of enamel degradation, leading to tooth decay and yellowing. Although the body has mechanisms for natural enamel repair and protection, improving enamel health is a major objective of dentistry and public health concern. Furthermore, the maintenance of healthy enamel is critical for enhancing teeth strength and appearance.
Unlike bone, which is composed of living cells capable of regeneration, dental enamel is constructed largely of mineral hydroxyapatite, Ca10(PO4)6(OH)2.1 The oral environment endures a constant cycle of mineral loss and gain, and the calcium phosphate crystals in enamel can dissolve when exposed to acids from foods or oral bacteria—a process known as demineralization. Remineralization works to restore calcium and phosphate ions to enamel, and the structure of hydroxyapatite allows for ion substitutions in the crystal lattice during this process. Maintaining appropriate levels of calcium and phosphate ions in saliva is essential for oral health, and the interface of enamel and saliva is of key importance since it is where both demineralization and remineralization processes occur (see Figure 1).