Why a Crown?
A crown is used when your tooth is either severely broken down because of decay (cavities) or it is exhibiting signs of fracture (pain to chewing). A crown covers most if not all of your tooth. This serves to protect the remaining tooth. Without a crown your tooth is liable to fracture and require extraction (removal). A bridge is used to replace one or more missing teeth. Fixed bridges are a more economical way to replace teeth than implants.
There are three basic material types used in the construction of your crown(s) and/or bridge. The type used is dependent on several factors. These factors are where in your mouth the crown will be, how much stress will be placed on the crown and is it in a cosmetic zone?
Porcelain fused to metal (PFM)
This is the traditional crown type which is has been used to restore teeth for many years. It is constructed of two materials, a gold alloy and porcelain. It's primary advantage is strength combined with esthetics. Usually, posterior (molar) bridges are constructed of this material. The porcelain is baked on at very high temperatures and thus gets bonded very intimately to the metal substructure leading to the increased strength.
It is this type of crown that has seen the most change over the years. New materials and methods have made this the treatment of choice for nearly all instances where a crown will be placed on a front tooth. But they are no longer limited to front teeth as the material strength has improved and is quickly becoming the standard. Most of these are bonded into place which makes them "become" a part of your tooth. A distinct advantage of this type of restoration is that it is somewhat translucent and appears more realistic than a PFM type restoration. In other words, it looks like a real tooth.
Gold has been present since the ancient Egyptians. It is a durable, non-corrosive and malleable material that is well suited to dental restorations. The only downside is cost and the fact that it does not bond to the existing tooth structure. It is primarily used in situations where the tooth is short and there is not much room for the ceramic materials. There are still situations where gold may be the material of choice.