"Using the technique, we can see all the way to the pulp-more than five millimetres inside a tooth," says Professor Andreas Mandelis of U of T's Department of Mechanical and Industrial Engineering. "It can reveal suspicious regions invisible to the naked eye below the surface of the tooth."
Using a device similar to a laser pointer, Mandelis and his team directed near-infrared light at different frequencies towards human teeth. The light, upon penetrating a tooth, slightly heated it and generated infrared radiation that revealed cavities. Higher frequencies worked best to reveal defects near the surface of a tooth, while lower frequencies uncovered problems deep below the enamel. This method of heat-generating laser light is called depth profilometry.
While standard X-rays can reveal existing cavities, he says, his team's photo-thermal technique can expose defects at very early stages of development, prompting preventive treatment. It also avoids the need for a heavy lead apron to protect patients from hazardous X-rays. The technique may have further applications in detecting skin and sub-dermal cancers. It can also detect flaws in metals, coatings or electronic devices.