Sensitive tooth after treatment. Coloured scanning electron micrograph (SEM) of the surface of a sensitive tooth. Teeth can become sensitive when the enamel covering the crown (visible part, dark grey) of the tooth wears away to expose the underlying dentin (brown). This tooth has been treated with a toothpaste containing nantin, a biocomposite of mineral (hydroxyapatite) crystals and protein that lays down an enamel-like material on the damaged tooth. Magnification: x1,650 when printed at 10 centimetres wide.