Tooth remineralization is the natural repair process for non-cavitated tooth lesions, in which calcium, phosphate and sometimes fluoride ions are deposited into crystal voids in demineralised enamel. Remineralization can contribute towards restoring strength and function within tooth structure.

Demineralization is the removal of minerals (mainly calcium) from any of the hard tissues: enamel, dentine, and cementum. It begins at the surface, and may progress into either cavitation (tooth decay) or erosion (tooth wear). Tooth decay demineralization is caused by acids from bacteria in the dental plaque biofilm whilst tooth wear is caused by acids from non-bacterial sources. These can be extrinsic in source, such as carbonated drinks, or intrinsic acids, usually from stomach acid coming into the mouth. Both types of demineralization will progress if the acid attacks continue unless arrested or reversed by remineralization.

When food or drinks containing fermentable sugars enter the mouth, the bacteria in dental plaque rapidly feed on the sugars and produce organic acids as by-products. The glucose produced from starch by salivary amylase is also digested by the bacteria. When enough acid is produced so that the pH goes below 5.5, the acid dissolves carbonated hydroxyapatite, the main component of tooth enamel. However, the pH threshold for dissolving dentin ranges from 6.2 to 6.4. The plaque can hold the acids in contact with the tooth for up to two hours, before it is neutralized by saliva. Once the plaque acid has been neutralized, the minerals can return from the plaque and saliva to the enamel surface.

However, the capacity for remineralization is limited, and if sugars enter the mouth too frequently then a net loss of minerals from enamel produces a cavity, through which bacteria can infect the inner tooth and destroy the latticework. This process requires many months or years.

Remineralization occurs on a daily basis after attack by acids from food, through the presence of calcium, phosphate and fluoride found in saliva. Saliva also acts as a natural buffer to neutralize acid, preventing demineralization in the first place. If there is reduced saliva flow or reduced saliva quality, this will increase the risk of demineralization and create the need for treatment in order to prevent demineralization progression.

Saliva function can be organized into five major categories that serve to maintain oral health and create an appropriate ecologic balance:

As the demineralization process continues, the pH of the mouth becomes more acidic which promotes the development of cavities. Dissolved minerals then diffuse out of the tooth structure and into the saliva surrounding the tooth. The buffering capacity of saliva greatly impacts the pH of plaque surrounding the enamel, thereby inhibiting caries progression. Plaque thickness and the number of bacteria present determine the effectiveness of salivary buffers. The high salivary concentrations of calcium and phosphate which are maintained by salivary proteins may account for the development and remineralization of enamel. The presence of fluoride in saliva speeds up crystal precipitation forming a fluorapatite-like coating which will be more resistant to caries.

Besides professional dental care, there are other ways for promoting tooth remineralization: