Why Do Some Dental Crowns Have Black Lines Near The Gum Area?

Great question-3 answers-First, the type of crown can affect the  color of your gum tissue-we use to make our porcelain fused to metal crowns(PFC) with collars at the area that fits on your tooth(at the gumline).  We thought it was better for your gum tissue.  Now, we do porcelain margins which do not show the collar as much.  We also use milled crowns made out of porcelain and other materials instead of the PFC.  Second, if you have a old root canal tooth the color of the tooth can be black and show at the gumline margin, especially when you have recession-Very difficult to completely cover although dentists do know tricks to hide it sometimes.  Third,  you can have black decay at the gumline. You must go to a dentist to discuss this and find out if the tooth is fine. 

Usually it is due to the type of crown - porcelain to metal.  These crowns have a metal substructure with porcelain baked over the top.  This metal can show through at the gumline over time especially if there is any gum recession.  Also if the tooth underneath the crown has had a root canal and metal post placed in it that can discolor the entire tooth and look dark also.

Fortunately technololgy has advanced where metal substructures are not needed in most cases and restorations can be metal free and beautiful long term.

Up to the last few years, most dental crowns were made with a metallic lining and porcelain cover.  It is this metallic lining that often shows through the porcelain, especially noticeable with the front teeth.  Thanks to modern dental materials, we rarely use any metal in the crowns that are made today.  So dark lines should be a thing of the past.  If you or someone you know has such crowns, you should consult with a dentist experienced in all-ceramic crowns and veneers to discuss replacement.

For many years the material of choice for fabricating a front tooth crown was porcelain baked atop a metal substucture.  As the patient got older and the gumline receeded the edge of the crown that was originally hidden under the gum became exposed revealling the edge of metal under the porcelain.  Nowdays, with newer more fracture resistant materials, a metal free porcelain crown can be used on front teeth which eliminates the possibility of future visible dark lines.

Black lines around the crowns usually are due to the metal content under neath. Metal does not belong in a wet area like the mouth. So, my advice, when it comes to replace these crowns, upgrade them to a full porcelain crown.

Good luck,