- I had these teeth all marked for cavities. My name is Mr. Tooth Decay. This is a tub of Crest. I had these teeth all marked for cavities and they were just right for it too. They were feasting on treats. They weren't going to see their dentist and they weren't brushing with a fluoride toothpaste like Crest. Because Crest helps enamel fight cavities. Why, why did you have to show up? [Announcer] Because fighting cavities is the whole idea behind Crest.