Porcelain-fused-to-metal crowns

A porcelain-fused-to-metal crown (PFM) could be considered to be a hybrid of the other types of crowns, in the sense that it is composed of two different types of materials. One is a metal alloy that is used to create that portion of the crown that fits directly on the tooth. The other is porcelain. The porcelain forms the tooth-shaped aspect of the crown and gives the crown a white tooth-like coloration.

Why choose a porcelain-fused-to-metal instead of an all-ceramic crown?

It is easy to imagine circumstances where a white porcelain crown would need to be placed instead of a metal crown. But why might a porcelain-fused-to-metal crown be placed instead of an all-ceramic one? Here are some of the reasons.

The metal substructure of a porcelain-fused-to-metal dental crown gives this type of restoration much greater strength than an all-ceramic crown. The metal substructure of a PFM crown provides for a more accurate fit over the tooth than an all-ceramic one.

What are the disadvantages of porcelain-fused-to-metal crowns?

» Porcelain breakage is possible.

It is possible that a part of the porcelain portion of a PFM crown will separate from its underlying metal substructure. The fabrication process associated creating porcelain-fused-to-metal crowns is complex and technique sensitive. While separation of the porcelain is not usually a problem, the potential for this event does exist.
      The degree to which this type of event is a problem will vary. Some problems are loss of tooth function, compromised cosmetic appearance, or the creation of a situation that makes maintaining oral hygiene difficult. The porcelain lost from a PFM crown cannot be reattached or replaced with new porcelain. It can be possible that dental bonding can be used to make a patch, although the long-term success of this type of repair is tentative. If the chip is just minor, no repair may be needed. At the other extreme however, a broken crown may need to be replaced with a new one.

» The appearance of a porcelain-fused-to-metal dental crown may not be as lifelike as an all ceramic one.

Most dentists would probably agree that an all-ceramic dental crown (due to the way it handles light) gives an appearance that looks more lifelike than a porcelain-fused-to-metal crown. Additionally, a weakness of PFM crowns in general is that with traditional fabrication techniques their metal substructure can show at the edge of the crown (or will show if gum recession occurs) or else can cast a tint in the overlying porcelain. This should be a concern that you should discuss with your dentist. There are a couple of ways by which they can overcome this difficulty. You should know what their plans are.

» Greater tooth reduction is needed.

If a porcelain-fused-to-metal dental crown is chosen over a gold crown, there is the disadvantage that the former requires slightly more tooth reduction than the latter. Gold crowns can be as thin as 1.5 mm on their chewing surface whereas PFM crowns need to be at least 2 mm thick. This factor will probably only be of minor concern to the dental patient. However, it can play a significant role as the dentist plans and determines what type of crown might be suitable for a particular situation.

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