Many dental clinics are able to manufacture crowns onsite while you wait—assuming the crown is plain porcelain, and intended for an anterior tooth (which are the front teeth that are most visible). Rear teeth (posterior teeth) must withstand significantly more occlusal bite force (physical pressure) than their front cousins. This often requires a special type of dental crown.

Metal

The best crown for a rear tooth that handles a high level of bite force is a metal one. Stainless steel is rarely used to crown a molar, but gold and gold alloy makes for a highly-functional dental crown. Unfortunately, the cost can be prohibitive and it's not as though the end result looks natural. Instead, a dental lab can manufacture, to your dentist's precise measurements, a porcelain fused to metal crown (PFM).

PFM Crowns

A PFM crown is realistic-looking porcelain attached to a strong metal frame. When it comes to molars, the strength of a PFM crown can be preferable to an all-porcelain crown. The tooth requires less modification than it would with an all-porcelain crown, and the finished crown will be a lot stronger too—allowing it to cope with many years of occlusal bite forces. What sort of modification does a tooth need before receiving a crown?

Modifications

A crown fits over the entire tooth, but to do so without preparing the tooth would make the crowned tooth dangerously bulky, exerting uncomfortable pressure on neighboring teeth, and even causing them to shift. A thin layer of the tooth's surface enamel is gently shaved away to accommodate the dental crown. Because porcelain isn't as strong as metal, more of the tooth's surface enamel must be removed for a porcelain crown.

Gum Line

A PFM crown requires less enamel removal than its porcelain counterpart. But that's not to suggest that the crown is entirely without drawbacks. The base metal alloy used to manufacture the metal frame may ultimately become visible at the gum line. The crowned tooth can subsequently develop a gray ring at its base. The location of a molar means that this isn't necessarily a concern, but it can be avoided.

Precious Metals

You get a choice in the metal of your PFM crown, and a precious (or noble) metal alloy containing gold and other precious metals is best. They can retain a high degree of compressive strength while remaining incredibly thin, meaning only a fraction of the tooth's enamel must be removed. The color of the frame also means that there will be no future discoloration affecting your dental crown.

Such a specialist crown must be made in a dental lab, but in terms of performance and your experience as a patient, when a molar needs a crown—your best bet is a PFM crown made with a precious metal alloy. 

For more info, contact a local dental lab.