A tool that can use sound waves to identify early stages of tooth decay by measuring the mineral content of teeth is under development in Australia.
Tooth decay begins by acid-forming bacteria eating away at the enamel, causing minerals to leach from it, softening, and weakening the tooth.
Sometimes dentists can identify this demineralisation by seeing a change in the colour of the tooth, or by looking at x-rays.
They also use sharp probes that test the hardness of the enamel, and find where the rot has set in, but all such probes can be painful and cause unnecessary damage to the teeth.
But PhD researcher David Hsiao-Chuan Wang, from the University of Sydney, and colleagues are now developing a less invasive new technique to measure mineral content of teeth, using sound waves generated by laser pulses.
"We want to be able to be able to quantify mineral content of the dental enamel," ABC Online quoted Wang as saying.
He added: "We can keep the laser power below a damaging threshold."
Laser pulses aimed at the tooth set up a series of high frequency sound waves (ultrasound) that travel through the enamel surface, penetrating it to different depths.
As a soundwave moves through a demineralised part of the tooth, it changes its speed, which can be detected.
Each soundwave penetrates to different depths of the enamel, depending on its wavelength, enabling a profile of the tooth to be built up, showing where decay has begun.
The researchers first tested the system on different known materials, before testing it on extracted human tooth.
They still have to test the system on teeth in patients, but firstly they need to develop a convenient handheld device and obtain ethics permission to trial it in humans.
Wang said that a prototype of the hand-held device could be ready in two years.
Professor Ian Meyers of the Australian Dental Association has said that testing the technique in the mouth is important, as saliva affects the property of teeth enamel.
Meyers also said that when decay was detected early, fillings could be avoided by either stopping the demineralisation through better oral care.
Otherwise, it could also be possible to re-mineralise the tooth by using products specifically designed for this purpose.
He said that the new technique could add to the range of tools available for dentists to identify early stages of decay, as long as it is affordable
Wang has estimated that the new tool would cost "below 50,000 dollars", and complement rather than replace conventional methods.
He said that the ultrasound technique would be particularly useful in research, especially in evaluating the effectiveness of remineralisation treatments.
The study has been published in the journal Optics Express.