Characteristics of Early Caries Lesions in Enamel

The enamel demineralization defect has a lower mineral distribution in the surface layer in comparison to the adjacent sound enamel and also a lower interprismatic mineral content. The first stage of enamel demineralization is characterized by removal of interprismatic mineral content and in the subsequent stages a well defined surface layer formation occurs which constitutes early caries lesion (4). Although early investigators like Hollander and Saper (47) in 1935 had noticed this subsurface demineralization white opaque spot, they mistook it to be a photographic artifact. However the work of various other researchers like Applebaum, Thewlis, Besic, Coolidge et al., Gray and Francis (3, 12, 21, 41, 87), on white opaque enamel lesion and new experimental techniques like microradiography (42), polarized light experiments (23, 78), microhardness data (30), and electron microscopy shed new light in understanding the early caries lesion in enamel. These studies have demonstrated that a porous and mineral-rich surface layer covers an enamel lesion and the morphology differs a little from that of sound enamel while body of the lesion which comprises the subsurface area has low mineral content (10–70 vol %). The early caries lesion in enamel is characterized by a prominent perikymata pattern and focal holes (6, 44, 88). The main drawback of the numerous experimental techniques is that they are static measurements of caries progression at a particular time period whereas the carious process is time-dependent and is in a constant state of dynamic equilibrium wherein a balance is struck between demineralization and remineralization. Surface layer (SL) covering early enamel lesions