The MDM system is a modified standard medical microscope similar to what doctors use to examine people's ears. A special light source has been attached to this microscope to provide different colors of light that can shine in the mouth. This microscope also has a digital camera attached to it so that researchers can take pictures of fluorescence and reflectance in the mouth in order to record what is seen with the different light colors. Researchers want to study the pictures in order to better understand the differences in fluorescence and reflectance from normal and abnormal cells.