Types of crowns.
Porcelain (ceramic) / Metal / Porcelain-fused-to-metal
Which makes the right choice for you?
Crowns can be fabricated out of an assortment of materials. This includes: 1) Metal (gold, metal alloy), 2) Ceramic (porcelain, engineered ceramic), or 3) A combination of both.
Each type has its own unique advantages and disadvantages. All-metal crowns are known for their strength and durability. Some types of all-ceramics are known for the superior aesthetics they can provide. Porcelain-fused-to-metal crowns offer the middle ground between the two.
Types of crowns.
I) All-metal dental crowns. / "Gold" dental crowns.
Some crowns are made entirely out of metal.
The classic metal crown is one made of gold, or more precisely, a gold alloy. Actually, there are a number of different types of alloys that can be used for crown fabrication. Some of these metals are silver in color, rather than yellow like gold.
Advantages of gold crowns.
Having a gold dental crown made can be an excellent choice. Here are some reasons why:
A) They're long lasting. - Gold crowns (and metal crowns in general) are very strong and can be expected to withstand even the heaviest biting and chewing forces well.
They will not chip. It would be uncharacteristic for a gold crown to break. And of all of the different types of crowns, gold ones probably have the greatest potential for lasting the longest.
B) They're kind to neighboring teeth. - The gold alloys that are used to make dental crowns have a wear rate that is about the same as tooth enamel. This means that a gold crown won't create excessive wear on the teeth that oppose it (the teeth that it bites against).
C) They're easy for a dentist to work with. - Alloys that have a high gold content are typically very workable metals (they have favorable physical properties). This characteristic can aid a dentist in achieving a very precise crown-to-tooth fit. (For more information, use the "types of alloys" link above.)
Disadvantages of all-metal crowns.
They're not white. - About the only disadvantage of metal dental crowns is their appearance. And because of this, they're not usually placed on teeth that are readily visible when the person smiles. They can, however, make a great choice for some molars, especially bottom ones.
If you are considering a metal crown, take our advice on this point. Before giving your dentist the go ahead to make it, check with your spouse first. They're the one who will be looking at your smile, and your shiny new crown, the most.
Related Page: Selling scrap gold / old dental restorations.
Consider a porcelain "window."
Some parts of an "all-metal" crown can look white. - The can be times when a patient wants or needs the strength, durability and predictability that an all-metal crown can offer but the way the one would look would be simply too objectionable. As a compromise, it is possible for metal crowns to be surfaced with porcelain on their side that shows. Dentists refer to this type of option as a veneer or "window."
Others will still be able to see a hint of the metal that surrounds the porcelain. They'll also be able to see the all-metal chewing surface of the crown. But this option may make having a metal crown a possibility where otherwise it would not.
II) Porcelain dental crowns.
Dental crowns that show prominently when a person smiles are usually either made entirely out of porcelain (or dental ceramic) or else have a veneering of porcelain on their surface (porcelain-fused-to-metal crowns).
A) All-porcelain dental crowns.
All-ceramic crowns are just that. They are fabricated in a fashion where their entire thickness is porcelain (or some other type of dental ceramic).
Advantages of all-ceramic crowns.
There's no better looking type of crown. - Due to their life-like translucency, ceramic crowns can be the most cosmetically pleasing of all of the different types of dental crowns. And for this reason, they often make an excellent choice for restoring front teeth.
It is, however, important to understand that not all types of all-ceramics are created (fabricated) equally. Single-appointment ceramic crowns (milled from a single cube of material) can't offer the same superior aesthetics as one handcrafted by a dental technician using a series of layers and different shades of porcelain.
Disadvantages of all-ceramic crowns.
Concerns about strength and longevity. - The overall strength of all-porcelain dental crowns can generally be considered to be less than all-metal and PFM crowns. However, those made out of one of the modern manufactured dental ceramics may not suffer from this drawback as much.
While they can be a good choice for front teeth, due to the hefty chewing and biting forces that humans can generate, all-ceramic dental crowns may not be the best choice for some back-tooth applications. Your dentist's judgment will be required on this point.
B) Porcelain-fused-to-metal dental crowns.
Porcelain-fused-to-metal dental crowns (PFM's) are somewhat of a hybrid between metal and porcelain crowns.
When they are made, the dental technician first makes a shell of metal that fits over the tooth. A veneering of porcelain is then fused to this metal (in a high-heat oven), giving the crown a white tooth-like appearance.
Advantages of porcelain-fused-to-metal crowns.
A) They're strong. - Due to their great strength, PFM dental crowns can make a good choice for either front or back teeth.
As a class, this type of crown would only place second to all-metal in terms of strength and durability. And just like them (and in comparison to some types of all-ceramics that don't), PFM's have a very long, well documented history of providing lasting service.
B) They're natural looking. - For some people, and some applications, the big advantage of a PFM crown over an all-metal one is simply that it's tooth colored.
Disadvantages of porcelain-fused-to-metal crowns.
There are some disadvantages associated with porcelain-fused-to-metal crowns (which no doubt your dentist will try to minimize as much as is possible). They include:
A) The "dark line" phenomenon. - The metal that lies underneath the crown's porcelain can sometimes be visualized as a dark line found right at the crown's edge. A dentist will usually try to position this dark edge just underneath the tooth's gum line. But, if a person's gums happen to recede, this dark line can show, thus spoiling the crown's appearance.
B) Achieving superior aesthetics can be difficult. - While the cosmetic appearance of PFM crowns can be excellent, they often are not as aesthetically pleasing as all-ceramic ones.
For the most part, this difficulty comes from the fact that the crown's metal substructure must be masked by covering it with relatively opaque (less lifelike) porcelain. While this requirement doesn't create a problem in all cases, it often presents challenges and results in aesthetic compromises.
C) Durability. - It's possible that the porcelain on a PFM crown will chip or break off. (It would generally be expected that a PFM crown would pose less risk to catastrophically crack or break than most all-ceramic types. Of course all-metal crowns avoid this complication all together.)
If porcelain breakage does occur, it's very difficult to make a lasting repair. The most predictable solution is typically making a new crown. As a compromise, some minor chipping may just be smoothed over or polished.
D) They may wear opposing teeth. - The porcelain surface of a PFM crown can create (possibly significant) wear on those teeth that it bites on or rubs against. (Many types of all-metal or all-ceramic crowns are more bio-compatible in this regard.) This issue might be especially important for people who brux (clench and grind) their teeth.
This potential is greatest in those cases where during placement the crown's "bite" needed to be trimmed and the crown's surface was not subsequently re-glazed (treated in a high-heat oven) or at least thoroughly smoothed and polished.