  Here we quantitatively evaluate the early stages of mechanical and
morphological changes of polished human enamel surfaces induced by soft drinks
using atomic force microscopy. With an increase of the immersion time in soft
drinks, we found a significant increase of surface roughness (Ra) and a
considerable decrease of elastic modulus (E) of the enamel. The prismatic
structure of enamel was clearly observed after a one-hour immersion in
Coca-Cola, which shows its strong erosion effect. A high surface roughness of
enamel results in a high chance of cavities due to easier bacterial adhesion on
rougher surface, while a drastic deterioration of the mechanical properties of
the enamel weakens its protection property. Our findings show the variation of
enamel surface at the very beginning stage of etching process by acidic drinks,
which can also be applicable to the etching mechanism of enamel surface by
other sources.
