Caries progression through human enamel and dentin
Donald J. Kleier (UCD)

Polarized light microscopy
In this study a thin diamond circular saw was used to section human teeth that exhibited clinical caries (dental decay). This tooth was first radiographed using several different techniques and films. The ground section was imbibed with quinoline and then illuminated with polarized light. The polarized image that appears here showed the true extent of the caries process through enamel (rounded outer layer to the right) and the depth of its penetration into dentin (inner layer that is predominantly blue). These findings were correlated to the radiographic image of the same tooth in an attempt to understand the difference between what we see clinically on a radiograph and what we would see histologically if that information could be available to us. This type of research proved histologic caries is actually far advanced compared to what the clinician sees on a radiograph.