The Prescription: E-Max or Zirconia?

The Prescription: E-Max or Zirconia?

As a dentist, how do you decide whether to prescribe an Emax or Zirconia restoration? Did you know that this question is one of the hottest topics in dentistry today? What are the laboratory components to this decision and why does it matter to the clinician and patient? No doubt the clinician gets to make the final decision and armed with the facts, that decision should be good for everyone. Every day, we answer client questions about Zirconia or Emax, so we decided to put some of the Q&A on this blog. Let’s start with a simple, but familiar always and never chart to offer some insight into laboratory thinking on these restorative choices. 

The first bullet point for making a Zirconia vs Emax decision lies squarely on the color of the dentin. If the original tooth color is what you desire, then the dentin color will likely be perfect for an Emax restoration. Whenever we attempt to dramatically bump up the value (brightness) of a tooth with Emax, the dark dentin becomes the enemy and the failure rate can rise rapidly. Fig.#1 and #2. 

      Figure 1 

      Figure 2

Placing an Emax crown on a preparation this dark will rarely, if ever, yield an acceptable esthetic result.  Now, the logical question is, why doesn’t the lab use an opaque ingot or block out the inside of the crown? We firmly believe if the clinician does not remedy this dark dentin issue prior to impression, an odious result is predictable regardless of the Emax ingot choice. Sometimes the ingot choice can help, but it must complement the characteristics of depth, color and translucence of the desired shade. Risky for remakes and lost chair time here folks!

The magic of Emax is that it doesn’t refract light as well as Zirconia which allows it to draft the color it is bonded to (dentin). This means that it will likely draft the color of ceramic opaque that we might place on the core to block out the dark dentin. We can never be absolutely certain what result the combination of dark dentin, ceramic stain and the Emax restoration will really present once it has been polymerized. Three different color sources are merging and it can be a moving target. We have used this block-out procedure with some success, but a growing number of high profile clinicians feel this procedure may be contraindicated for bonding protocol. While we await those studies, we continue to use Zirconia on dark dentin cases because we just have a more consistent esthetic outcome. We do believe that when the dentin color is ideal, it is hard to make a more beautiful and lifelike restoration than with Emax!

Emax crowns and veneers with mildly dark gingival dentin can be beautiful on some cases by making the transition from the gingival to the body of the restoration more believable.  Some patients may see this as a compromise, so patient education is warranted. Very dark dentin moves the case from veneers to jackets with Zirconia being the best choice. This Emax crown, Fig. #1 and 2 is a great candidate for Zirconia, because it refracts light better than Emax and the lab can use ceramic opaque to block out the inside of the cemented crown without much risk of altering the desired shade. This is also the reason that Zirconia over implant crowns and bridges has been so effective for us. Our block-out strategy leaves the metal abutment optically undetectable after the Zirconia crown is seated and saves the clinician the onerous cost of precious metal.

Another caveat to consider when doing a case with Emax veneers and Zirconia crowns on the same arch, would be to use the same layering porcelain on both materials. Emax layering porcelain can be safely baked to Zirconia to minimize the optic differences of the two materials. Never try to bake the Zirconia porcelain to the Emax!

Remember to consider the dentin color first rule and you will immediately enjoy more success and less confusion. To make sure the laboratory can assess how to best manage the color on your all-ceramic case, always use the Ivoclar (natural die material shade guide). Fig #3. 

                                                           Figure 3

        Figure 4

With Zirconia or Emax, always include a photo of the closest dentin tab and remember to rehydrate the dentin first. Fig #4. 

The Emax system has corresponding light cure to match their dentin guide including resin stains that the lab can use to create a life like surrogate prep. Fig. #5.This exercise will allow the technician to see what the restoration will look like in the mouth and learn what can and cannot be done over off-colored dentin.

Take a look at Fig. #6 and see how the red die relief shows through the emax crown and then see how it looks on the surrogate prep. Notice that the dark orange band that the lab placed on the surrogate prep, Fig. #5 showed up perfectly on the final restoration. Fig. #7. 

         Figure 5 

         Figure 6

Figure 7

Now take a look at these Zirconia crowns that were seated on dark dentin. Fig. #8. Zirconia and Emax generally have better esthetics than metal ceramics for some very profound reasons. The margins certainly look a whole lot better with all-ceramic and when cutting into the inter-proximal of a bridge, the dull color of opaque over metal doesn’t reach out and bite you!

If you desire extra support on the occlusion, would your patient prefer seeing metal or does full color monolithic sound better?  I could go on and on with this rant, but suffice to say that this lab wouldn’t go back to “the good ole days” if precious metal was free. In fixed restorative, all-ceramic restorations are winning the day and they are metal free! 

“Our restorative world is now changing for the better!” -Dene LeBeau

“I recognize that there will be diverging opinions on this blog and for the sake of time, I intentionally left some areas of information out. I welcome all opinions or questions and I look forward to some healthy technical dialogue!”