Stronger than bone, enamel is the hardest and the most mineralised substance of the human body -- one of the reasons why human teeth can survive for centuries after a person has died. It envelops teeth in a protective layer that shields the underlying dentin from decay, said an U-S release.

Enamel demineralisation is caused by bad oral hygiene. Not brushing, for instance, can lead to the build-up of dental plaques, and bacteria in these plaques will absorb sugars and other carbohydrates a person chews and produce acids that will dissolve the minerals in tooth enamel.

These findings were described in the latest issue of Optics Express, Optical Society's (OSA) open-access journal.