A crown covers a weak tooth, or a tooth after a large treatment, and gives it back shape and strength. For many years the common crown was porcelain fused to metal. Today the more common choice in our clinic is a zirconia crown. That does not mean an older crown “did not work”. It means there is a newer material that solves a few clear weaknesses of the previous generation.
What a porcelain-fused-to-metal crown is
A porcelain-fused-to-metal crown, also called PFM, is built in two layers. Inside there is a metal cap. Porcelain in the color of the tooth is built over it.
The metal gives strength. The porcelain gives the look. The problem is that they are not the same layer. Over the years the porcelain can chip or peel off the metal. If the gums drop a little, a grey line can appear at the edge of the crown. That is the line people sometimes see next to older crowns.
What a zirconia crown is
Zirconia is a strong ceramic in the color of the tooth. The crown is made outside the mouth, usually from one piece, and then bonded to the tooth.
There is no metal cap under porcelain here. The whole crown is made from the same strong material, so there is no outer layer that can break and leave metal showing.
Why zirconia is preferred today over the previous generation
A few clear points:
- There is no grey line at the gums, because there is no metal at the margin
- There is no porcelain layer sitting on metal that can peel or chip
- The whole crown is tooth-colored. It is much more aesthetic, so it also suits front teeth better
- There is no metal in the crown. So it can also suit people who are sensitive to metals
- It is a single layer. So during tooth preparation, less tooth structure is usually removed than with a porcelain-fused-to-metal crown
The material itself sits well with the mouth. The practical difference is fewer places where the crown chips or changes color over the years. That is not a promise that the crown lasts “forever”, and not a claim that every metal crown was bad.
The common drawback is cost. A zirconia crown is usually more expensive than a porcelain-fused-to-metal crown.
When a crown is needed at all
A crown is considered when too little tooth is left for a stable filling, after a wide restoration, or when the tooth needs a full covering to take chewing load. If enough healthy tooth remains around the area, a partial restoration is sometimes enough and the whole tooth does not need to be covered. I wrote about that in the article on inlays, onlays and overlays.
If the tooth is already missing, a crown alone does not bring it back. A missing tooth has a different path, such as a restoration on an implant. I wrote about that in the article on implant, abutment and crown.
What the treatment looks like
There are usually three visits, and sometimes more:
- The tooth stump is shaped to receive the crown
- A temporary crown is built
- An impression or a scan is taken
- The final crown is bonded and the bite is adjusted
After bonding there can be mild sensitivity for a few days. If the tooth feels high when biting, do not “get used to it”. Come back for an adjustment. I wrote about sensitivity after a new restoration in the article on sensitivity after a filling.
How long a crown lasts
A crown does not come with a fixed expiry date. It is better to think in terms of three to five years. With proper care it can last much longer, even ten to fifteen years. That depends on daily cleaning and on check-ups at the clinic. Without that, the margins can wear or get a new cavity, regardless of the crown material.
Bottom line
A porcelain-fused-to-metal crown served well for many years. Its weakness is the two-layer build: metal inside and porcelain on top. A zirconia crown is made from one tooth-colored material, with no metal line and no layer that peels or chips off metal. Tooth preparation is also usually more conservative. That is why it is the common choice today when a crown is needed.
I also explain these details at the end of the examination: how much tooth is left, whether a crown is needed at all, and which material suits that tooth.
Sources
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The American Dental Association explains that a crown covers a weak tooth or a tooth after major treatment, and that it can also be used to strengthen a tooth or improve its shape.
ADA MouthHealthy – Crowns -
The American Dental Association materials page describes zirconia as an alternative to porcelain-fused-to-metal crowns: a strong tooth-colored ceramic used for crowns in the front of the mouth and in the back.
ADA – Materials for Indirect Restorations
The information in this article is intended for educational purposes only and does not constitute a substitute for personal medical advice. It is recommended to consult a qualified physician before making any treatment decision.