Well my parents both had terrible teeth, my dad has full dentures and my mom a partial since they were young, so they were adament that I brushed well. When I had gotten my full set of adult teeth, the dentist told my parents that my teeth were very shapely and that I was at a huge risk for a lot of cavities. My parents paid to have the sealant/coating put on my teeth to prevent cavaties. So I assume that it has worn off and that is where that cavity had come from, and that I am probably going to have tons of them now!! LOL
