Asked by: Anonymous
The strongest teeth are natural, healthy ones and these teeth are not white. At least, not white like the colour of paper, or even the colour of piano keys. They are a couple of shades darker than that. The enamel itself is a blueish white colour, but it is also somewhat translucent so the yellow of the dentine beneath it shows through to make the overall colour of the teeth either light grey or light yellow.
If your teeth are darker than that, it may be due to heavy smoking or possibly certain rare metabolic disorders. This can be corrected by a combination of bleaching and polishing off the top layer of enamel, but both of these will permanently weaken the teeth.
Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.