When a tooth is particularly affected by caries, a simple conservative treatment and filling is not enough to reconstruct it, as the dental element would still remain less resistant to masticatory loads, especially if previously devitalized.  Therefore we should “cover” it with a crown (cap) in ceramic or metal-ceramic (fixed prosthesis).  This structure spans the dental element down to the gum and protects from recurrent caries, and consists of a “shell” cemented on abutment tooth like a cap (in this case the tooth is filed to “make room” for the crown).  A crown consists of an internal metal substructure (today the materials mostly used for this are gold alloy or platinum, cobalt-chromium steel, zirconium oxide, rarely titanium) coated with ceramic body that provides a natural appearance to the crown.  Another type of crowns are made entirely of ceramic, which means yet better aesthetics, however slightly less resistance – these crowns are used when aesthetics is of utmost concern.

A crown is the best choice in case of very affected and destroyed teeth, as it not only performs an aesthetic function, but also protects the tooth - contains it inside an “armor” and consolidates it in a single block.

If the dental element is completely devoid of the crown or there is too little of the tooth intact, for example as a result of extensive decay, or after a root canal treatment (devitalization), a sturdier support is needed for the crown.  A crown buildup allows creating a steady support so the crown has something substantial to hold.  A crown buildup can be done simply with bonding composite material or may require a post to create a stronger bond.

Sometimes a healthy tooth is used as a pillar of a bridge and is also covered with a crown:  two crowns (which are placed on two teeth adjacent to edentulous zone) are supporting (holding) the crowns which cover the edentulous area.  This method is being gradually replaced by more advanced techniques of dental implantology.