Polarized light evaluations of enamel sections have been useful in describing the early caries lesion and alterations in structure upon further demineralization or remineralization. Generally, it provides information on absorption color and boundaries between minerals of differing refraction indices. Materials such as enamel act as beam splitters and divide light rays into two parts. Polarized Light microscopy (PLM) in turn exploits the interference of split light rays, as they are reunited along the same optical path to extract information about materials. Essentially, polarized light microscopy allows the visualization of areas with different porosities. The histologic features seen under a polarized light microscope allow the examiner to distinguish carious and non-carious enamel by their respective distribution of pores (Gwinnett, 1966). Polarized light examination of enamel specimens is a well-established procedure in which it is customary to view quinoline-imbibed sections orientated so that normal enamel is blue/green in color (Gilmour and Edmunds, 1998).
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