Some crowns are made of porcelain and metal. The base of the crown that connects to the existing tooth material is metal covered with porcelain for a more natural look. The advantages to porcelain fused metal crowns are their durability and lower cost. However, the only drawback is that the metal at the base of the crown can sometimes show up as a dark border near the gum line. This may not matter if you are getting a crown placed on a back tooth that won’t show, but on a front tooth it can deter from the natural appearance.