Dear Dr. DiTolla,

I have seen you lecture a few times and I also have been using Glidewell for some of my restorations. My question is concerning IPS e.max^® full contour crowns (Ivoclar Vivadent; Amherst, N.Y.). I was using IPS e.max zirconia for my replacement for PVCs. I have recently started using the IPS e.max CAD product after watching your video from Glidewell. The idea seems to make sense, especially since I have had some problems with my overlay porcelain on my zirconia crowns chipping or breaking. I know Christensen had some concerns about these crowns as well. So my question is, do you prefer the IPS e.max full contour as your replacement for PVC and have you had many problems with them? Also, would you use them anywhere in the mouth?

– Dr. Jeffrey L. Schultz
Bellaire, TX

Dear Jeff,

No, IPS e.max CAD has not totally replaced PFMs for me, although I suppose they could if you wanted to avoid metal. I still like cast gold for second molars, for example. In areas of the mouth that aren’t esthetically significant (such as molars), I would rather go with a PFM for the additional strength. If I were forced to do an all-ceramic material, it would probably be a zirconia-based restoration, such as Lava™ (3M™ ESPE™; St Paul, Minn.) or Prismatik Clinical Zirconia™. Zirconia is not as strong as a PFM, but it is stronger than IPS e.max CAD. IPS e.max CAD is my “go to” all-ceramic crown for bicuspids and anterior teeth. The fact that IPS e.max CAD is the lowest remake product of all of our permanent crowns in the lab goes a long way with me; it seems to work in everyone’s hands.

– Dr. DiTolla

Dear Dr. DiTolla,

Thanks for the reply. I have been using zirconia for several years now just about anywhere in the mouth. I have had a few problems with the overlay porcelain chipping and even breaking. I also have had some failures with PFM, but more so with zirconia crowns. The reason I thought IPS e.max would be better than zirconia is that the problem is not the zirconia itself, but it is the overlay porcelain and since the IPS e.max is stronger than the overlay porcelain, wouldn’t the e.max be the strongest in a way? I know everyone talks about how strong zirconia is, but again, the problem is not the zirconia breaking, it is the porcelain on top of it that can fail. This is just a thought because I haven’t done many IPS e.max cases and do not know how they hold up over time.

– Dr. Jeffrey L. Schultz

Dear Jeff,

I completely agree. I have some insanely long span zirconia bridges in the mouth and though the framework has never broken, they are prone to chipping based on the overlying porcelain that is used. Furthermore, if they do chip, it is way harder to attempt a repair than a PFM because there is no metal to bond to. And cutting off eight units of zirconia based restorations? Total pain in the butt, and potentially dangerous to the teeth, as it is easy to inadvertently cut into the tooth as the bur breaks through the zirconia.

IPS e.max is as beautiful as you would expect since it has no underlying coping. However, we don’t have enough long-term data to vouch for its strength in all situations. The only IPS e.max fracture I have had is one that was placed with temporary cement; suffice it to say, a PFM would not have broken in that situation. At approximately 300 MPa compressive strength, IPS e.max is at the minimum of what can be cemented conventionally. If it were any weaker, it would have to be bonded like Empress, although I know of a few colleagues who bond all of their e.max into place. I know the average dentist has no interest in bonding all of their restorations into place.

I encourage you to place some e.max, specifically the IPS e.max CAD. This product is easily the lowest remake product in our lab for permanent crowns. Just keep in mind that it is still an all-ceramic and should not be placed in all clinical situations. In my mind, PFMs and cast gold still can’t be beat in those posterior regions with high biting forces and limited room for occlusal adjustment.

– Dr. DiTolla

Dear Dr. DiTolla,

I have been reviewing my splint therapy. I came across your DVD on the hard/soft splint. I enjoyed your DVD and have seen you speak in Asheville at one of Ross Nash’s seminars at the Groove Park Inn. I am a fan of yours and respect your ideas and contribution. That being said, does the soft part of the comfort splint increase nighttime bruxism? I want to start using these splints for protection, but I’ve read about this concern.

– Dr. Tommy Spears
Maryville, TN

Dear Tommy,

I have heard that concern also, but only anecdotally. Unfortunately, that is the only way I can answer you as well. My experience with the Comfort H/S™ (hard/soft) splints in my own mouth and with my patients is that the inner soft layer is too thin to be spongy enough to be chewed on in that fashion. I also have a full soft athletic mouthguard that I have worn and that one is fun to chew on. It is more important to me to have the soft layer on the inner aspect of the splint so that the splint will continue to fit the patient even if their teeth shift a little. I used to fabricate full hard splints and have worn several myself. I was always disappointed how the splints would no longer fit at some point due to the physiological shifting of the teeth. I have a lot of patients who report they don’t need to wear their splints every night, and I want to assure them that it will still fit two months later if it has been sitting in their drawer. For patients who wear their splints every night, there should be no problem making them a full hard splint and having it continue to fit for many years. If TMJ and muscle symptoms decrease or disappear with a hard/soft splint, it stands to reason that nighttime bruxism has not increased.

– Dr. DiTolla

Dear Dr. DiTolla,

I was placed on hold one time when I heard you talk [in your “On-Hold Clinical Tips”] about a bur that you use to remove zirconia/e.max crowns. What is that bur?

– Dr. Fred M. Rabinowitz
Plano, TX

Dear Fred,

There are actually two different burs for zirconia and e.max. For zirconia, I like the ZIR-CUT™ Bur from Axis Dental (Coppell, Texas). I have tried to use other burs on zirconia (such as typical diamonds and carbides), but these are the only ones that actually cut. I cut through the porcelain on a zirconia crown with the Razor carbide from Axis Dental, and then switch to the ZIR-CUT Bur to get through the zirconia coping itself. I use the same Razor carbide to cut off e.max crowns. Since e.max does not have a substructure, there is no need to change burs to cut these crowns off.

– Dr. DiTolla

Dear Dr. DiTolla,

Hello, I am currently a dental resident and I have a quick question for you. In the journal Dental Economics^®, you said that you can reapply glaze to porcelain intraorally by using a high-torque electric handpiece. I would like to know, which polishing system and pastes do you utilize for this procedure? Thank you for your help.

– Dr. Brandon G. Katz
Baldwin, NY

Dear Brandon,

Thanks for the question! Well, I don’t apply glaze to the crown intraorally, per se; I return a glaze-like polish back to the crown. Truth be told, if you sent a crown back to the laboratory to have it reglazed after it had been in the mouth, nine out of 10 labs would do the same thing. They use an electric lab handpiece, which you could do extraorally, and this is one of the big reasons I use electric handpieces intraorally as well. I go through the three steps of the CeraGlaze^® kit from Axis Dental (axisdental.com or any dental dealer) on all teeth I have adjusted intraorally. And then for anterior teeth, especially on the facial surface, I use a round 12 mm soft bristle brush with some Diashine (both from vhtechnologies.com) to place a very high shine on these esthetic restorations. The key for me is the amazing amount of torque I get from my KaVo ELECTROtorque handpieces. It’s all about the torque!

– Dr. DiTolla