Laminated zones in carious human dental enamel.

Laminated zones within the body of carious lesions were studied by polarized light microscopy and transmission electron microscopy. Areas from within and surrounding the laminated zones, precisely selected using light microscopy, were argon-ion-beam thinned and examined by transmission electron microscopy. Laminated zones were present in approximately 7% of the samples studied. Polarized light microscopy showed variation in mineralization from zone to zone and the enamel surrounding the zones in the body of the lesion. Laminated zones whose central region showed approximately 1% of space when examined in air and whose boundaries showed approximately 2-4% of space when imbibed in quinoline were selected for ultrastructural studies. Electron microscopy showed the laminated zone to be less demineralized than the surrounding enamel in the body of the lesion. The ultrastructure of their central regions was similar to healthy enamel but their boundaries showed demineralization which increased into the body of the lesion. Within the central region of lamination there was greater evidence of resistance to demineralization rather than the presence of remineralization.