Currently, X-rays and metal probes are used to check cavities, but they fail to detect weaknesses in the enamel in time to repair the surface.
Lead researcher David Wang sought to determine whether the propagation of sound waves through the enamel could provide an early warning.
The study showed that short, low-energy pulses from a laser generate weak bursts of acoustic waves in the surface of the enamel.
In tests on an extracted tooth, Wang detected these vibrations by collecting infrared laser light reflected from the surface of the tooth.
He found that changes in mineralisation of the enamel, which signal the onset of decay, appear to cause characteristic changes in the pattern of acoustic waves.
Wang will now be working for a more compact system.
"The ultimate goal is to come up with a quick, efficient, cost-effective and non-destructive way to evaluate mineralisation," New Scientist quoted him as saying.
The findings have been published in the journal Optics Express.