Today I went to my dentist to replace crown that he did a month ago. There was too much of metal margain sticking out so he’s replacing it with one that has porcelain margain at the front.Today when I had my old own crown taken out I realized that my tooth (thats still alive) has darkened out significantly. Does the discoloration means that there’s something wrong with a tooth?Should I be worried (Sorry for grammar mistakes English is my 4th language).