Scientists have perfected hydroxyapatite, a material for mineralizing bones and teeth. By adding a complex of amino acids to hydroxyapatite, they were able to form a dental coating that replicates the composition and microstructure of natural enamel. Improved composition of the material repeats the features of the surface of the tooth at the molecular and structural level, and in terms ...

The smile may be the most common and flexible expression, used to reveal some emotions, cover others and manage social interactions that have kept communities secure and organized for millennia. But how do we tell one kind of smile from another? “When distinguishing among smiles, both scientists and laypeople have tended to focus on true and false smiles. The belief ...