Add Yahoo as a preferred source to see more of our stories on Google. How does purple toothpaste work? It uses color theory’s principle of complementary colors. Complementary colors are shades that ...

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Thanks for your great questions, Amelia. I’m a dentist, so I know a bit about how toothpaste works and what we used before it was invented. Toothpaste makes your mouth smell fresh and feel clean. If ...