why would someone in their mid 30s "probably had an extra enamel coating applied"? I've never heard of that. Of course, they give you “super fluoride” when you go in for cleanings, but that's not an extra coat of enamel. I'm pretty sure there is not such technique, when your adult teeth reach their full size that's pretty much all the enamel they'll ever have, dentists can't just apply another layer or we'd all be cavity free.