Q. I got a porcelain fused to metal crown about 5 months ago and I have a couple of questions. I was looking at it today and I saw this white line between where the metal and porcelain meet. What is that? Also there is a black horizontal line in the middle of my crown on the porcelain part. It isn’t at the gum line, what could this be? Also how long does it take a crown like this to adjust because my gums are still sensitive around it? Thanks!