Is there any way for a "porcelain-fused-to-metal crown" to avoid a dark line at the gumline?

The best way to prevent having a dark line above a metal crown covered with porcelain, is to get an all porcelain crown.  Not only are all porcelain crowns the most cosmetic, but they are also pretty durable.  If you are considering a crown for the posterior teeth, you should get a crown made of zirconium, which in many cases is stronger than metal.  Good luck and I hope this helps. Follow me if you have more questions.Sarah Thompson, DMD

The preferable restoration would be an all porcelain crown. If a PFM is used, the lab can place a "porcelain shoulder margin" which allows the metal to stop about 1mm from the margin and the margin is only porcelain. The metal sometimes will still reflect through the tooth and root causing a darker shade if there is any recession over time. Good luck.