I’ve always been diligent about brushing my teeth at least twice a day. Who doesn’t love a minty-fresh, picture-perfect smile? But six or seven years ago, I learned that my technique was sorely lacking. I tended to rush through the job, scrubbing furiously, and after decades of overly vigorous cleaning, my teeth had developed an uncomfortable sensitivity to heat and cold. My dental hygienist explained that the enamel, or protective layer, was wearing thin and exposing the more sensitive dentine underneath.