A black line at the gumline or a tooth that looks fake because of a flat, bright un-natural color or a tooth that is too bulky compared to the adjacent teeth are sure indications of a crown that is an esthetic failure. With appropriate materials, procedures, and skill lifelike crowns will blend in naturally with adjacent natural teeth.

What Causes the Dark Line?

The dark line is associated with an old porcelain crown. The dark line originates from the edge of the crown where the porcelain and the metal meet at a knife-edge at the gum line. At the knife-edge, a very thin amount of the metal always shows. One of the illusionary techniques dentists have used was to hide the thin dark line under the gum line. Over time, the gum tissue would recede and expose the dark line. In some patients the dark line would show through the gum and make it appear dark as well.

How Do You Get Rid of It?

The only way to eliminate the esthetic problem is to replace the crown. The most beautiful crown for a tooth is, without question, all-porcelain or all-ceramic. With porcelain fused to metal crowns, there has to be an opaque layer put over the metal to block out its color. This makes it impossible to have a translucent restoration that mimics the translucency of natural teeth. Only with pure porcelain or pure ceramic can you have such translucency. And these three basic categories of crowns for front teeth: bonded all porcelain, extra strength all porcelain, or porcelain fused to metal.

Bonded all porcelain - It is made entirely of porcelain or other ceramic material. Now the type of porcelain used for crowns for teeth by itself is not very strong. The way a cosmetic dentist will handle this is he or she will bond the crown to the tooth, thus giving it plenty of strength to function.
This type of crown has the nicest appearance. It mimics the appearance of nature to the point where it is difficult to tell that it is not a natural tooth. An all porcelain crown costs more than a porcelain fused to metal crown. And while an all porcelain crown is strong enough for front teeth, it may not be strong enough for some back teeth in some patients with an extra strong bite.

Extra strength all porcelain - There are some new ceramic materials that have extra strength - so much so that they don't have to be bonded. However, they aren't as esthetic as the bonded all porcelain crowns. Some brand names of crowns that are this type are Procera crowns, InCeram crowns, Cercon Zirconia crowns, Lava crowns, and Cerec crowns. While they don't have an opaque metal core, most of them have an opaque white core, so they aren't as esthetic for front teeth. They don't tend to develop the dark black line at the gumline that porcelain fused to metal crowns do, but they can still reveal a sharp color difference where the crown meets the tooth. They also tend to be a little more abrasive on the opposing teeth that chew against them.

Porcelain fused to metal - This style of crown is referred to as a porcelain fused-to-metal crown because it uses tooth-colored porcelain on the outside and it uses metal under the porcelain for strength. A black line at the gumline of a crown is caused when the underlying metal framework supporting the porcelain shows through. A properly done crown with an acceptable margin should have no black line. They tend to have a very fake-looking opacity, and they will tend to get a black line at the gumline after a few years. This line may not show when the crown is first placed but shows later, as the gum recedes. But porcelain fused to metal is substantially stronger than the all porcelain crown. Further if ever you need a crown discuss all the possible options and get more natural smile. Like to seek a consultation , contact our dental office.
Dr. Vinod Chandel MDS. (Prosthodontics) AIIMS New Delhi
Advanced Dental Care,Prosthodontic and Implant Centre
SCO 157/1 Sector 37-C, Chandigarh
Phone no. 2691001, 09815131898