sensitive+whitening nano-hydroxyapatite toothpasteDavids sensitive + whitening nano hydroxyapatite toothpaste uses naturally sourced and derived ingredients to safely and effectively reduce teeth sensitivity, remineralize enamel, fight plaque, and whiten teeth. Nano hydroxyapatite was first developed by NASA to help strengthen the teeth of astronauts returning from zero gravity environments, and were proud to make this same modern science available for your smile.