Porcelain-Fused-to-MetalRestorations (PFM):

PFMs are strong and are suitable for use in all areas of the mouth and in most clinical situations
Clinical success of PFM restorations has been proven through long-term research
Clinical research has shown that single PFM crowns will last for many years, and three-unit PFM bridges also have a relatively long lifespan
PFM crowns and bridges provide relatively good esthetics, especially during the first few years
Precision attachments can be used with PFMs, while zirconia restorations have not yet achieved this ability
PFM restorations can be used for long-span bridges and have proven to be an effective material choice in the longer term.
THE DOWNSIDE

It can be difficult to create highly esthetic restorations because of the metal substructure. The substructure must be masked with opaque and may remain slightly visible even after layering with porcelain. Opaque also prevents light from passing through the restoration as it would with a natural tooth.

Another potential problem with PFM restorations is gum recession. Over time, as gum tissue recedes, the metal margin of the PFM is exposed, creating a grayish colored line that isn’t esthetically pleasing. One way to overcome this problem is to use a porcelain margin, but this may not always be a practical solution.

PFM crowns are layered with feldspathic porcelain, which is a relatively weak material that wears opposing teeth at a very high rate.

The crown’s porcelain portion can also chip or break off. Next to all-ceramic crowns, porcelain-fused-to-metal crowns look most like normal teeth. However, sometimes the metal underlying the crown’s porcelain can show through as a dark line, especially at the gum line and even more so if your gums recede.