A dental crown is a tooth-shaped "cap" that is placed over a tooth as a covering to restore its shape and size, strength, and/or to improve its appearance.  The crowns, when cemented into place, fully encase the entire visible portion of a tooth that lies at and above the gum line.

A dental crown may be needed to protect a weak tooth (from decay, for instance) from breaking or to hold together parts of a cracked tooth, or restore an already broken tooth or a tooth that has been severely worn down.  In some cases, a crown is needed to cover and support a tooth with a large filling when there isn't a lot of tooth left, hold a dental bridge in place, cover misshaped or severely discolored teeth, or cover a dental implant. 

All-ceramic or all-porcelain dental crowns provide the best natural color match out of all other crown type and may be more suitable for people with metal allergies.  All-ceramic crowns are a good choice for front teeth.  Porcelain-fused-to-metal dental crowns can be color matched to your adjacent teeth (unlike the metallic crowns).  Next to all-ceramic crowns, porcelain-fused-to-metal crowns look most like normal teeth.  These crowns can be a good choice for both front or back teeth.