why is the gum line around my crown grayish? (photo)

Hello there,PFM crowns consist of metal that is covered by tooth colored porcelain. When the porcelain does not completely cover the metal, or the gums have receded and the metal is now exposed, you are left with this characteristic gray line that can give your gums an unhealthy appearance.  For my patients, I use Zirconia crowns to avoid this issue.  Good luck and I hope this helps. Follow me if you have more questions.Sarah Thompson, DMDSt. Louis, MO area (O'Fallon, IL)Real Self 100

The dark gum line is most probably caused by the metal edge of the crown showing through the gum. This is not a problem in the back area of the mouth. We prevent this by making the crown margin in porcelain rather than metal. Another way of preventing it is by doing all porcelain or zirconia crowns. 

An isolated grey tint of the gum tissue like visible in the picture could be due to a couple reasons. 1.  If the crown is a porcelain fused to metal crown and the gum tissue around the tooth is thin it can allow the metal of the crown to shine through, not harmful but not what you were expecting. 2.  If the tooth had a large amalgam or silver filling for a long period of time this can stain the gums as well. If the darkness was not present prior to the crown being placed it is most likely reason #1.