Laser Technique Able To Detect Developing Cavities

"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.

The study, which appears in the January issue of the Review of Scientific Instruments, was funded by Materials and Manufacturing Ontario.