Dental crowns give patients an alternative to tooth extraction when teeth are badly damaged. However, much like your natural teeth, dental crowns are not faultless. For instance, if you had a dental crown placed over a badly damaged tooth in the smile zone a few years ago, you may now notice that there is a black line around it at the gum line.

The most likely reason for this is that you have what is called a porcelain-fused-to-metal crown. These crowns consist of both porcelain and metal. While at first they may appear as white as your other teeth, over time, the underlying metal structure gradually begins to become more visible. As light cannot pass through them as it does natural teeth, the metal sub-structure appears much darker than the rest of the tooth.  

You Could Replace the Crown

Unfortunately, your best option is to replace your porcelain-fused-to-metal crown with an all-porcelain crown. All-porcelain crowns are composed of porcelain and therefore do not have a metal substructure beneath the porcelain surface. This type of crown of is usually recommended for teeth in the smile zone so they are indistinguishable from your natural teeth.

Not only are the edges of porcelain crowns translucent like those of your natural teeth, but they also allow light to pass through them as with your natural teeth. Porcelain-fused-to-metal crowns, on the other hand, are opaque in appearance. Although it is true that porcelain-fused-to-metal crowns are more structurally sound than all porcelain crowns, if the crown is in your smile zone, this isn't an issue.

Your front teeth are used for cutting, not chewing, and as such are perfect candidates for all-porcelain crowns.

A Dental Filling is Cheaper but Less Aesthetic

Purchasing an entirely new crown is expensive. If you are unable to fork out for a new crown at the moment, there is a temporary alternative. You could ask your dentist to place a filling over the dark edge. Using the same material that is used to fill cavities, composite resin, your dentist can hide the dark edge until you are ready to purchase a new crown.

However, keep in mind that this should only be a temporary measure. Dental bonding cannot completely hide the darkened edges of crowns. Bonding also stains over time and so will look out of sync with the rest of your crown. A dental filling will, however, tide you over for a few months while you save up for a new all-porcelain crown.

If you are embarrassed by the dark line at the edge of your crown, visit your dentist to make sure it isn't a cavity before taking any further action.