Crystal Growth During Remineralization

The process crystal growth during remineralization is complex and influenced by both the oral environment and the characteristics of the lesion. During periods when plaque fluid and saliva are supersaturated with respect to hydroxyapatite, demineralized enamel crystals can act as nucleation sites, allowing new mineral to precipitate from solution. These existing, partially demineralized crystals "seed" new crystal growth. However, this process can be disrupted by the presence of various inhibitors in the oral cavity. Saliva contains proteins such as statherin and proline-rich proteins that regulate crystal growth to prevent unwanted mineral precipitation. These natural inhibitors can also interfere with the regrowth of enamel crystals during remineralization. As a result, newly formed crystals tend to be small, contain numerous structural defects (such as missing ions), and are more soluble than mature, well-formed crystals.

Despite these challenges, when crystals are consistently exposed to a large volume of solution that remains supersaturated with respect to hydroxyapatite, a slow refinement process known as Ostwald ripening can occur. During this process, smaller, less stable crystals dissolve, and the released ions contribute to the growth and perfection of larger, more stable crystals. This leads to the gradual formation of fewer but larger, more stable, and less soluble crystals, enhancing the structural integrity of remineralized enamel. This natural healing mechanism underscores the importance of maintaining prolonged periods of supersaturation in the oral environment - achievable through fluoride exposure, adequate salivary flow, and reduction of acid challenges - to support optimal crystal maturation and long-term enamel resistance.