A device provides incident light on oral structures, switchably between two states. In the first state, incident light causes autofluorescence of byproducts of decay, and an optical filter between the oral structures and either the user's eyes or a visualizing apparatus yields visually distinguishable appearances for that autofluorescence depending on whether the tissue is healthy or unhealthy. In the second state, the incident light is of a color composition that yields a substantially “white” spectrum after passing through the filter.
