There are currently two main ways in which dentists look for cavities: visual inspections and x-rays. Visual inspections usually only detect cavities once they're relatively advanced, however, and x-rays can sometimes miss cavities on the tooth's biting surface. Now, technology being developed at Toronto's York University could provide a more effective alternative.
In the non-invasive new process, each of a patient's teeth would first be exposed to a laser light source. A low-cost device known as a thermophotonic lock-in imaging (TPLI) tool would then use a long-wavelength infrared camera to image those teeth. If any cavities were present, the light exposure would cause them to still be emitting a small amount of thermal infrared radiation, which would be detected by the camera.
Although it's still in the developmental phase, the technology has already been successfully tested on extracted human molars. These were made to start demineralizing by being immersed in an acid solution for 2, 4, 6, 8 and 10 days. While the TPLI was able to detect cavity-causing lesions after just two days, a visual inspection didn't detect them until the 10-day mark.
A paper on the research was recently published in the Journal of Biomedical Optics.