Enamel is composed of mineralized crystals in an organic matrix. This unique structure provides channels through which minerals, such as calcium and fluoride, and acids can flow.
We no longer think of dental caries as a simple, uncontrollable, linear progression from acid demineralization to a frank clinical lesion. We now believe the caries process is dynamic and involves demineralization and remineralization.
Normally, equilibrium exists between mineral loss (demineralization) and mineral gain (remineralization). Demineralization occurs when acid lowers the pH at the tooth surface. This causes calcium, phosphate, and other minerals to diffuse out of the enamel and creates a subsurface lesion.
Remineralization represents the opposite reaction. During remineralization, mineral is redeposited in the subsurface lesion. Fluoride, even in low concentrations, can enhance the remineralization of enamel and may actually result in a crystal structure that is more caries resistant. In this process of demineralization and remineralization, enamel caries can actually be reversed providing the outer surface layer of the enamel is still intact. Once the outer surface layer is lost, the potential for remineralization is also lost, and the tooth must be restored.
Note: Intact surface layer and remineralization area.)
Role of Saliva
The flow, dilution, buffering, and remineralizing capacity of saliva are also recognized to be critical factors that affect, and in some ways regulate, the progression and regression of the disease. If the oral environment is balanced and favorable, saliva can contribute to strengthening of the tooth by supplying the components to help build strong apatite structure.