I have a porcelain on metal crown on a tooth I believe is dead. I recall root canal in 2002 and I had a gold crown, but replaced this for aesthetic reasons in 2009. lately the crown has felt larger & noticeable in my mouth. I don't have pain but I occasionally have an ache in that area. I'm anxious that I will lose the tooth. Might I just need a new crown or is it a sign that the tooth has weakened beyond repair? The edge of my gum/crown is black & getting darker.