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Dear Dr. DiTolla,

What is your best choice to cement IPS e.max® anterior cosmetic crowns (Ivoclar Vivadent; Amherst, N.Y.)? I have had a few recent failures due to the bacterial leakage, which is causing darkness under the crowns and gray gum lines.

Sincerely,

– Kenneth V. Lee, DDS
Auburn, California

Hello Ken,

The only gray gum lines I have seen with e.max crowns are on teeth that have been endodontically treated or have had tetracycline staining in conjunction with a thin gingival biotype. I place a depth-cut in the gingival third during my prep sequence to ensure that the e.max crown will be at least 1 mm thick in that area. The type of black marginal staining that occurs from microleakage is something that I haven’t seen since I stopped using etch-and-rinse techniques for bonding veneers onto dentin. I cement all of my e.max restorations with Ceramir® Crown & Bridge luting cement from Doxa Dental Inc. (Newport Beach, Calif.), but before I knew about Ceramir, I placed the majority of my e.max crowns with the resin-modified glass ionomer RelyX™ Luting Plus (3M™ ESPE™; St. Paul, Minn.).

If you watch the Reverse Preparation presentation at glidewelldental.com, you will see how I make sure my margin is subgingival and how I ensure I have 1 mm of reduction in the gingival third. In my mind, those two factors are much more likely causes for what you are seeing than your cement choices.

Hope that helps.

– Mike

Dear Dr. DiTolla,

I’ve read about your Reverse Preparation Technique for prepping PFMs, full-contour zirconia crowns, etc. Do you have anything similar for prepping veneers?

Sincerely,

– Larry Keating, DDS
Fulton, New York

Hello Larry,

That’s a great question that I haven’t been asked before. Certainly the same principles that you’d use in the Reverse Prep Technique could apply to veneers as well; you’d just want to use smaller versions of the burs. The reality is that most of the time when I’m looking at a veneer case these days, I’m trying to do everything in a minimal fashion. Typically what we’ll do is we’ll look at a patient’s occlusal photograph or we’ll take the study model and set an orthodontic arch wire along the cusps. This arch wire represents the ideal arch form. First, we’ll look for everything that’s laying out to the facial of that wire, because we know we’re going to have to remove some tooth structure to get the preps into the ideal shape. We know that we’re not going to have to do anything that’s found to the lingual of that wire. In fact, some of those lingual surfaces might just end up being used for straight no-prep veneers.

What I do now for veneer cases is a combination of minimally prepped teeth and no-prep teeth together. Using something like the Reverse Prep Technique for eight or 10 veneers in a row won’t actually be all that useful, because you’re only having to reduce so much and trying to stay within enamel whenever possible. The process is kind of an approximation, and there really aren’t standardized depths like there are with preps for zirconia or IPS e.max. With veneers, because we’re in the anterior, we don’t have to live by the demanding bite-force rules of the posterior. The anterior allows for much more creativity in terms of the preparation and in terms of how thick the restoration is going to be.

Hope that helps.

– Mike

Dear Dr. DiTolla,

What do you use to reline BioTemps® Provisionals (Glidewell Laboratories; Newport Beach, Calif.)? Can you use Structur® Premium from VOCO GmbH (Cuxhaven, Germany)?

– Joseph Ramos, DDS
Frankfort, Indiana

Hey Joe,

When I first got here, everything we used to reline BioTemps was a methyl methacrylate, because it was the only material that would bond directly to the BioTemps. When I started using bis-acryl products like the one you mentioned, the BioTemps team told me that it wasn’t going to work because it wouldn’t bond to the material. Whether or not that was true, I never got a chance to find out because any time I relined BioTemps with a bis-acryl material it never came out. Whether that’s due to mechanical retention or whether it was actually some sort of chemical bond, I’m unsure. I had many years of luck using bis-acryls just like the one you mentioned without any problems.

The advantage of using a methyl methacrylate is that you have the opportunity to pump it up and down and make sure you’re not going to accidentally lock it into place.

One nice middle ground is available from DNG America (Englewood, N.J.), the makers of Luxatemp®. They have a product called Luxatemp Automix Solar, which is what I’m currently using to reline my BioTemps. The interesting thing about Luxatemp Solar is that once you put it into the BioTemps and seat it onto the preps, it’ll set on its own into a doughy stage that enables you to pump the provisionals up and down and make sure there are no undercuts. In fact, during this stage you can take it out and do trimming with scissors or even with a disk. You can then put it back in the mouth and make sure it all looks good. Once you approve of it, take it out and light-cure. That’s the final cure that brings it to its full hardness. You should give Luxatemp Automix Solar a try.

– Mike

Dear Dr. DiTolla,

I’m confused about the indication of cementing Lava™ Ultimate crowns (3M ESPE) using Ceramir. I thought you had said that Ceramir can be used as an all-around cement on any crown, but when I spoke with the company rep they said to follow the manufacturer’s instructions, which do not mention Ceramir as an appropriate material.

– Arnold Chernoff, DDS
Evanston, Illinois

Dear Arnold,

I have said that, and it’s mostly correct. But ultimately, you are correct, because you cannot in fact use Ceramir for all types of crown. What I meant by saying that is that it is usable for every type of crown that I actually use. I predominantly use full-contour zirconia, like BruxZir® Solid Zirconia. And now with BruxZir Anterior I can use BruxZir all the way up to the front with good translucency. I sometimes use IPS e.max crowns. I don’t do PFM single-unit crowns anymore, but I still do PFM bridges because those end up being stronger than a BruxZir bridge.

What I don’t do (and what most of our dentists don’t do) is a lot of Lava Ultimate crowns or VITA ENAMIC® crowns (VITA Zahnfabrik; Bad Säckingen, Germany) or any of those other nano-filled resin crowns. Regardless of brand, they all have a flexural strength of around 250 MPa. Anything under 300 MPa of flexural strength has to be bonded into place and cannot be cemented. And because Ceramir is a traditional crown & bridge cement and not a bonding material, you are absolutely correct that Ceramir is the incorrect choice for those Lava Ultimate restorations. In fact, those restorations could crack if they aren’t bonded into place correctly.

As of today, IPS e.max is the weakest crown that can be cemented. And it’s at about 360 MPa, which is way above the 300 MPa of flexural strength that’s required for cementing crowns.

– Mike

Chairside Magazine: Volume 10, Issue 3

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