Since teeth are designed in a bell shape, the space between each two adjacent teeth is filled with a piece of gum called papilla which is one of the most important aspect of a natural smile. In a natural smile this papilla fills the spaces between adjacent teeth completely, however this papilla can collapse and eventually get lost which will create what is called black triangle.
A black triangle in a person with high smile line ( someone who shows a lot of teeth and or teeth and gums during a full smile ) is an annoying imperfection to the smile that can cause the person to become very much self aware of this to the point where some people will eventually smile half way only where the upper lip doesn’t go all the way up to show this imperfection. Black triangle  be corrected in some situations, and in other situations it can’t ( which means lost forever).

• One of the main reasons that can cause an irreversible (a nightmare for patients and dentist) loss to the papilla is gum disease. Since gum is sitting on top of bone, loosing  bone due to a gum disease and calculus build up material on the teeth (which is full of bacterial) can cause the bone to break down and the gum on top of it follow leading to a black triangle. This situation can be handled, with regular check ups and professional cleaning of teeth, before it starts.
• Another reason is upper anterior teeth with roots that are divergent, which in many instances can be corrected with mild ortho with a traditional braces or with clear ones like Invisalign.
• Another reason is tapered teeth which cause the contact area to go closer to the incisal edges of the teeth and make it difficult for the papilla to close all this space. In this case the correction can be done either restoratively by bonding some composite to the side of each tooth to squeeze the papilla and close the space or by stripping the contact area between the upper anterior teeth slightly, and bringing the teeth closer together with ortho.
• And the last reason is untreated proximal decay in the anterior teeth, due to neglect, fear or finance.
  Your cosmetic dentist in Laurel MD can easily discuss this issue with you and talk about different options to correct it.