Zirconia vs. Emax Crowns

The first thing a patient should know is when a dental crown should be used by a dentist. Dental crowns are used in situations where the teeth are weak, worn and possibly broken or fractured. These are all situations where a dentist would use a dental crown.

Crowns have been around for a very long time. Because of advances in technology, the process has been streamlined down to other types of restorations such as onlays and emax restorations. When a dentist decides to use a dental crown, it is for the specific reason of trying to re-strengthen a tooth that is very weak. The dentist is aiming for long term success with the tooth.

EMAX

Emax is a specific type of porcelain called lithium disilicate and it is basically a block of porcelain. Because it is a block of porcelain as opposed to one that the ceramic artist or dental technician creates by hand, the block increases the strength factor of the material. Lithium disilicate is hard porcelain to begin with and that allows for its inherent strength to be kept with the restoration. With emax, there is no core material that needs to stay with this material because all the strength is built within the porcelain. EMax can be used as a core material whereby porcelain can be layered on the surface to increase the esthetic value of restoration for anterior eMax restorations.

ZIRCONIA

Zirconia is an interesting type of crown that has been used for the past eight to ten years continues to be used today. Most people know the phrase “cubic zirconia.” It is like a diamond substitute used in jewelry. The material used by dentists is not in the cubic form. It is in a form known as a tetragonal form that still has the hardness of zirconia but can be manipulated and used as a core material for dentistry. Instead of having to use metal as a core material for the strength of the crown, dentists are able to have a white material such as the zirconia. This material gets away from the metal aspect of dentistry. Since zirconia is a very hard substance, it is able to withstand a lot of the pressures caused by chewing.

Pure zirconia can be used as a crown and many dentists use this under the brand name “BruxZir crowns”. BruxZir crowns are primarily for people who have a lot of strength in their bite. People who do a lot of bruxing (teeth grinding or clenching) are in need of some material that is extremely strong. Pure zirconia crowns are very popular for that type of situation because these patients could break up restorations (including emax restorations) with their grinding and clenching. They are in need of extreme strength with these restorations. In the past, all these patients could use was metal on the surface. However, patients do not want to see metal now and that is why pure zirconia crowns are very popular. Patients are able to have something white back there instead of something that is gold.

ZIRCONIA DRAWBACKS

One of the drawbacks of zirconia is that the color is very opaque. EMax is a much more translucent material so it appears very natural when it is bound to teeth. The teeth have a certain amount of translucency because dentists are trying to mimic enamel. In comparison, the color of zirconia is not translucent and appears to be manufactured or artificial.

A zirconia restoration can be made to look more natural by bonding a layer of porcelain onto the core material. This is a popular way to make zirconia crowns aesthetic and very strong. However, just like the porcelain-fused-to-metal crowns, the zirconia crowns need two substances which are the core material and the layered porcelain. Therefore, the dentist has to remove more teeth structure to make room for that.

FRONT TEETH

Zirconia and emax can be used on the front teeth. However, zirconia cannot be used as a veneer material. It can only be used as a crown material. The one thing about zirconia that is still being researched is its ability to bond to tooth structure. There are people who say zirconia can be bonded to teeth but there is not enough evidence. Emax can be used as a veneer form and can be a very beautiful restoration when done correctly.

Zirconia and emax can both be used on front teeth but zirconia has to be in a crown form. Zirconia needs to have a micromechanical retention fit on the tooth which should be in the form of a crown. From there, the dentist can cement on the zirconia restoration.

The choice of which one to use depends on the individual patient and the strength factors. If a tooth is reasonably strong and a patient does not have a super hard bite, emax restorations would probably be the best way to go for the best strength and beauty.

COST

In general, the cost is about the same in that they are both premium restorations with a higher cost.

The cost is premium because the laboratory expenses are much higher in comparison to a gold restoration or porcelain fused to metal restoration. Because emax and zirconia are much higher in cost, the final cost is higher to the patient.

FELDSPATHIC PORCELAIN

There is another type of porcelain used by elite dentists. While zirconia and emax are nice restorations that mimic natural tooth structure, it takes skill to create a look and beauty that is indistinguishable to people looking at patients. The other porcelain material used by elite dentists is called feldspathic porcelain and is used primarily for a veneer-type of form. Within a very thin layer of porcelain, the ceramic artist is able to re-create nature so no one will be able to tell that a patient has dental veneers.

In order to control the end result, the patient needs someone who is adept at bonding on restorations as well as adept in the world of art and color and management. In order to create a beautiful smile, the dentist has to be artistic as well as a ceramic artist.

If the dentist manages the bite correctly then the restoration will have great strength. However, feldspathic cannot rival the strength of a zirconia core.

LIMITATIONS

Zirconia requires a very specific type of cement that is nerve-friendly. The sensitivity of the results of placing the zirconia crown can be very comfortable. The emax needs to be bonded on which requires an adhesive protocol that is very technique-sensitive and can lead to post-treatment sensitivity if not done correctly. What a patient considers to be a successful treatment versus unsuccessful is unrelated to the crown itself and related more to comfort.

MAINTENANCE

Do not use any abrasive toothpaste. Beyond that, do not have a hygienist use the routine type of pumice paste used to polish teeth because the grittiness is abrasive. It is going to scour the porcelain and the exterior porcelain will look horrible as time passes. A wrong polish or wrong toothpaste can start to scour the teeth and the glaze on the porcelain.

The key to maintaining long-term beauty of porcelain is maintaining the glaze of the porcelain. The glaze is super critical towards having long-term success in the smile. Micro diamond polishing paste can be used routinely to polish the restorations. At home, a gel or a paste can be used as long as it is not gritty.

FINAL THOUGHTS

Dental crowns are specifically used to re-strengthen a tooth that is very weak. Whether a dentist uses zirconia or an emax crown is dependent on the patient and how much strength they need from a crown. Patients should schedule a consultation with a board-certified cosmetic dentist to determine which option is the best choice for their dental needs.

Written by Cosmetic Town Editorial Team-MA

Based on an exclusive interview with Wynn Okuda, DMD, FAACD, FICD FICOI in Honolulu, Hawaii