What are Tooth Crowns?

Published:November 6th, 2011

For crowns and fixed prostheses, dentists all around the world believe that Porcelain-fused-to-metal restorations (PFM) to be the best type of care available. Over 50 years of research and clinical findings have shown that they are the most reliable type of restoration and have a low rate of failure. Although they are the primary type of restoration used, they do have some limitations:

  • After several years, the appearance of the ceramic stains placed on these restorations become lighter because of the consumption of acidic foods and drinks. This will create a mismatch between the colors of the teeth.
  • When the gingiva tissue recedes, the margins of the restoration become visible and obvious because it has a chalky or metallic look.
  • There is aggressive wear on the teeth opposing on the restorations or natural teeth. It must be noted that some types of ceramics are less prone to this than others.
  • Sometimes, chipping or fracturing of the ceramic from the metal substructure occurs.

While PFM restorations are clearly still the most popular choice, there are also other all-ceramic restorations that have increased in popularity. Listed below are the other all-ceramic restorations with their corresponding pros and cons.

Zirconia-based all-ceramic restorations

This type of restoration is most commonly used for crowns and short span fixed prostheses. The brands that have this include Lava and Cercon. The benefits of using zirconia-based restorations is that the teeth look good, the material has moderate strength, and has a history of moderately successful use spanning a period of 10 years. The disadvantages are that the process of creating these restorations are still being improved and the cost for them is high.

This is the only type of all-ceramic restoration aside from all-zirconia restorations that has the appropriate strength for fixed prostheses. Because of this, it is believed that since refinements in this type of restoration has increased its predictability and successful use, the zirconia-based restorations will continue to become popular over against PFM restorations.

Lithium Disilicate

This is most commonly used for single crowns, dental inlays and onlays, which are either made in laboratories or in a dentist’s clinic. The advantages in using Lithium Disilicate are that it produces a beautiful appearance, has moderate strength, and can be placed with traditional cements. In addition, placing this type of restoration only calls for a simple procedure. The disadvantages, on the other hand, include the fact that the restoration still needs to have further observation and research done on it and only single-unit restorations can be done using this material.

Many dentists have observed that aside from its aesthetics, significant breakage with this type of restoration does not occur in single crowns, both inlays and onlays, which shows that it will possibly have a continued and wider use in the future.

Leucite-inforced ceramic

Similar to Lithium Disilicate, this type of material is most commonly used for single crowns (inlays and onlays) which are made in labs or in a dentist’s clinic. Many brands carry this type of restoration, one of which is IPS Empress. This type of restoration has a beautiful appearance and matches the colors of the other teeth like a chameleon. The disadvantages, though, are that bonding must be done on the restoration and its strength is lesser compared to other all-ceramic restorations that are currently in use.

This type of restoration has been in use for many years however its success rate has not been that good. If lithium disilicate is able to prove itself as a good and dependable material for single-unit restoration, the use of this material will most certainly decrease.


Although it is most commonly used for single crowns and short span fixed prostheses, this type of restoration is still new and has not established its success yet. BruxZir is one of the many brands that have this type of material. There is lesser wear on opposing teeth compared to other types of restoration and is monolithic. Also, this material has strength. Because it is still new, it still requires a lot of research done on it to prove its long term use.

Metal (gold alloy) restorations

The most common uses of this type of restoration are all-full metal crowns on the first and second maxillary molars and the mandibular first molar. It is also used on inlays and outlays for all the posterior teeth. This is a strong material that is good for long-term use and causes minimal wear on opposing teeth. The disadvantages are that the material is expensive and its color is not aesthetically pleasing.

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