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Episode 028\n \nTeeth make eating possible, sharks scary, and smiles pretty. But when you have a cavity, you need to see a dentist. For over 200 years, dentists have been filling cavities with amalgams, which are mixtures of silver, mercury, and other metals. Since the 1970s, however, dentists have increasingly been using a new material called a composite, which is made by adding powdered quartz to a plastic resin.