Q & A with Archibald and Associates: What do Jed and John really think about zirconia and why do they use IPS e.max®?

Q: Are you still layering?

A: Yes, but it is patient and case specific. As you can see below (figure A), it is much different and more natural based than that of figure B. Most of our aesthetics are achieved from choosing the right IPS e.max translucency, we like to place detailed effects (or extra aesthetics) of stain and character just under the layer shown in figure A, and then covered with soft effects of porcelain shown as the yellow layer in figure A. This way we can achieve a layered light transmittance like natural teeth.

fig-D.jpg
Figure A
fig-B.jpg
Figure B

Q: Do you do monolithic and where?

A: Yes, since all we need is minimal room (see figure A) to get the “extra” aesthetics we need, typically we leave the posteriors and lower anteriors in a monolithic state. If we need added character we will layer the buccal only and leave the occlusion full strength. The aesthetics of IPS e.max Press Multi is so great; the visual plus of adding porcelain does not outweigh the down of strength loss. If it’s part of the occlusion we will leave it monolithic.

Q: IPS e.max Press Multi or Zirconia?

A: Every material has its positives and negatives. Let's focus on the facts:

    • IPS e.max is weaker than zirconia in a direct side by side comparison.
    • That being said, we have no scientific data showing the strength of “bonded” IPS e.max vs. cemented zirconia. Nothing bonds to zirconia and we have to rely on mechanical retention only.
    • We have personally done thousands of IPS e.max bonded and conventionally cemented with no problems. It’s a huge advantage to be able to bond.
    • We can press IPS e.max. Yes machines are awesome and are getting better, no one disputes that. But for the real discerning technician and dentist, IPS e.max press can (I emphasize can) get you a better organic fit and stronger material. Until machines are prepping instead of human hands that’s not going to change. (see figures C:1,2,3) Any mill enthusiast is welcome to try and come mill this case. Press / Milled is about a 500 / 0 count right now.
fig-E1
Figure C1
fig-E2
Figure C2
fig-E3
Figure C3
  • We do a lot of zirconia too. We do many large span bridges that need ultimate strength. Essentially right now if we have a bridge that needs a 3/4 PFM type of restoration we are doing so in zirconia. Knowing that the weakness of IPS e.max is strength (when compared to zirconia), and the weakness of zirconia is the lack of bond - you can use them in an educated manner.

Read Jed and John's latest case study with Dr. Gordon J. Christensen in Inside Dental Technology.