Should I get an eMax vs Zirconia crown for endodontically treated molar (tooth #26)?

[Nan]

I underwent root canal treatment in my upper molar (tooth 26), and had my tooth prepped to fit a crown.
I am looking into eMax (lithium disilicate) vs solid Zirconia for a crown.
Is it true that it is difficult to adjust a Zirconia crown after cementation (chairside) as opposed to eMax?
I am worried that if I choose a Zirconia crown and it will need an adjustment, the dentist might end up adjusting the healthy opposing tooth instead – (because of the difficulty in adjusting the Zirconia) and I would not be happy with that.
I should mention that my dentist took conventional (pvs) impressions of my my teeth, not digital.
Would eMax be preferred in terms of durability/wear/chairside adjustment? What would be my best bet between the two materials?

Attached is an X-ray of my molar (tooth 26) after root canal treatment with temporary filling, before crown prep.
I would greatly appreciate all insights and recommendations.

 

[honestdoc]

I recommend Zirconia crown for the molar. eMax has a tendency to fracture at that location. I have no problems adjusting Zirconina crowns and your dentist should not have to drill on opposing teeth. eMax would look beautiful on the front teeth although I see fractured anterior crowns very often as well. In restorative dentistry decision making, one must consider esthetics on one end of the spectrum and functionality on the other. It would be nice to have both but not as often as we like.

 

[MattKW]

I'd firstly prefer a stainless steel post for reinforcement of the core. I don't see much benefit of zirconia apart from near indestructibility. I prefer monolithic eMax (not layered) that will do just nicely and bonds better than zirconia. Conventional VPSis fine; digital is just the latest and greatest, but no significant difference. A good impression can be achieved by many different materials and techniques. My favourite used to be polyether (Impregum) for hydrophilicity, but not too tasty, and more expensive than VPS.

 

[Nan]

I'd firstly prefer a stainless steel post for reinforcement of the core. I don't see much benefit of zirconia apart from near indestructibility. I prefer monolithic eMax (not layered) that will do just nicely and bonds better than zirconia. Conventional VPSis fine; digital is just the latest and greatest, but no significant difference. A good impression can be achieved by many different materials and techniques. My favourite used to be polyether (Impregum) for hydrophilicity, but not too tasty, and more expensive than VPS.

Thank you for your reply. My dentist did a glass ionomer buildup without post/pin/screw, due to adequate remaining tooth structure. Would you still recommend an eMax crown considering the core buildup in my case?
Would you be able to specify the disadvantages/problems you have experienced with Zirconia crowns?
To note: I'm not a grinder or a clencher, but due to the fact that molar tooth #26 is in charge of most of the heavy chewing, I want to be able to chew comfortably without worrying about breaking my crown.

 

[honestdoc]

Of course different dentists will have different opinions. I respect Dr. MattKW's over 30 yrs experience. I'm the most experienced dentist at my location and by default, I see the most complicated cases, conduct peer reviews and take on ~5-8 walk-in emergencies each work day along with my full schedule. Bottom line, I see a lot a good work fail and a lot of marginal work still functioning.

I like Zirconia because I don't have to drill as much (drilling more achieves thicker stronger crowns). I cement Zirconia with Glass Iononmer because it bonds naturally to dentin and has desensitizing properties (desensitizing is not a priority after RCT).

eMax and resin cement will work. For resin cement, there are close to 10 generations of bonding systems with their own advantages & disadvantages. Unfortunately I see too many failed bonded resin cements. For eMax, the dentist has to drill more because it is not as strong as Zirconia. Modern zirconia crowns have better esthetics and I use many of them on anteriors. I've adjusted hundreds of zirconia crowns and drilled many RCT access holes and it is harder than eMax but I have no problems. The dentist will have to use diamond burs of various grits for more predictable results.

There are advantages and disadvantages of placing posts. The biggest problem of placing posts is weakening the roots especially molars with their smaller roots. US military dentistry research has shown at least~4 mm pulp chamber retention to be ideal.

In my opinion, VPS is still the most reliable and predictable impression material. Modern VPS has additives to make it more hydrophilic and accurate. Digital impression still lags behind in accuracy although to a non-dental professional like most patients, it looks amazing and futuristic. I leave the VPS impression 2 minutes longer than recommended to minimize tray separation stress distortion when the material is fully & predictably set.

 

[Nan]

Of course different dentists will have different opinions. I respect Dr. MattKW's over 30 yrs experience. I'm the most experienced dentist at my location and by default, I see the most complicated cases, conduct peer reviews and take on ~5-8 walk-in emergencies each work day along with my full schedule. Bottom line, I see a lot a good work fail and a lot of marginal work still functioning.

I like Zirconia because I don't have to drill as much (drilling more achieves thicker stronger crowns). I cement Zirconia with Glass Iononmer because it bonds naturally to dentin and has desensitizing properties (desensitizing is not a priority after RCT).

eMax and resin cement will work. For resin cement, there are close to 10 generations of bonding systems with their own advantages & disadvantages. Unfortunately I see too many failed bonded resin cements. For eMax, the dentist has to drill more because it is not as strong as Zirconia. Modern zirconia crowns have better esthetics and I use many of them on anteriors. I've adjusted hundreds of zirconia crowns and drilled many RCT access holes and it is harder than eMax but I have no problems. The dentist will have to use diamond burs of various grits for more predictable results.

There are advantages and disadvantages of placing posts. The biggest problem of placing posts is weakening the roots especially molars with their smaller roots. US military dentistry research has shown at least~4 mm pulp chamber retention to be ideal.

In my opinion, VPS is still the most reliable and predictable impression material. Modern VPS has additives to make it more hydrophilic and accurate. Digital impression still lags behind in accuracy although to a non-dental professional like most patients, it looks amazing and futuristic. I leave the VPS impression 2 minutes longer than recommended to minimize tray separation stress distortion when the material is fully & predictably set.

I appreciate your response.
You say there is less drilling with Zirconia, and I'm slightly concerned because my dentist had told me that the tooth preparation he performed would be good for either Zirconia or Emax, and that the margins were the main important factor here. Does that make sense?

Also, in terms of cytotoxicity and long term biocompatibility - would one material be preferred over the other? Can Zirconia be harmful in any way? Can Emax be toxic?

 

[honestdoc]

You have very good questions! Since eMax is not as strong as Zirconia, eMax needs more drilling to accommodate a thicker crown. I'm sure modern eMax has improved in strength though.

I don't know the exact details of cytotoxicity and long term biocompatibility of either materials. When a material has been approved for dental applications, we believe it has been thoroughly tested.

Dr. MattKW may have some valuable insights. That is the beauty of peer discussions.

 

[MattKW]

Neither has biocompatibility problems. I simply prefer eMax as a all-round use material as it can be resin-bonded to preparations whereas zirconia can't be truly bonded without special preparations. In most cases where the retention is good, then even bonding is of secondary importance. Monolithic eMax (or zirconia) is stronger than layered eMax (or zirconia). There's really not that much difference between either for a back tooth. As for post and pins, the pins don't add much, but I have seen failures with simple cores that haven't been reinforced with at least one post. The biggest problems with posts is if they're too thick or long, then their usefulness diminishes, and the risks increase (been there, done that). I like to use one medium length post in largest canal, and a shorter and thinner post in a secondary canal.

 

[honestdoc]

Dr. MattKW is correct on all counts. Glass Iononmer cements do not bond to Zirconia crowns. I prep for Zirconia like I prep for Full Gold with mechanical retention. In dentistry, we tend to remember the failures and forget the successes. I see a lot of eMax with resin bonded cements still in function (otherwise they would be taken off the market). I just don't trust bonding as much as mechanical retention due to a lot variables involved. Many patients think bonding without a lot of real world science. Bottom line, (I know it is a different scenario) when dentists evaluate posterior composites on x-ray, we tend to see "black" lines around them. What are those black lines? Is it micro gaps? Is it pooling of excess bond? Is it recurrent or start of recurrent caries? Since many of the composites are done by the same provider evaluating it, we tend to think pooling. As in my previous post, I mentioned there are close to 10 generations of bonding systems with varying strengths and weaknesses. Ironically I attended 2 lectures (many years ago before the 8th generation was developed) given by John Kanca DMD who is regarded as the father of adhesive dentistry and who the bonding system products go through for review.

Dr. MattKw is also correct on layering. I can't think of any reason to do that other than for esthetics which goes back to my earlier post mentioning esthetics vs function.

 

[Nan]

Dr. MattKW is correct on all counts. Glass Iononmer cements do not bond to Zirconia crowns. I prep for Zirconia like I prep for Full Gold with mechanical retention. In dentistry, we tend to remember the failures and forget the successes. I see a lot of eMax with resin bonded cements still in function (otherwise they would be taken off the market). I just don't trust bonding as much as mechanical retention due to a lot variables involved. Many patients think bonding without a lot of real world science. Bottom line, (I know it is a different scenario) when dentists evaluate posterior composites on x-ray, we tend to see "black" lines around them. What are those black lines? Is it micro gaps? Is it pooling of excess bond? Is it recurrent or start of recurrent caries? Since many of the composites are done by the same provider evaluating it, we tend to think pooling. As in my previous post, I mentioned there are close to 10 generations of bonding systems with varying strengths and weaknesses. Ironically I attended 2 lectures (many years ago before the 8th generation was developed) given by John Kanca DMD who is regarded as the father of adhesive dentistry and who the bonding system products go through for review.

Dr. MattKw is also correct on layering. I can't think of any reason to do that other than for esthetics which goes back to my earlier post mentioning esthetics vs function.

You say that glass ionomer cements "do not bond to zirconia crowns", but I am confused because you wrote earlier: "I cement Zirconia with Glass Iononmer because it bonds naturally to dentin and has desensitizing properties (desensitizing is not a priority after RCT).
Can you clarify?

I asked my dentist about the difficulty of Zirconia adhesion, and he said that it would not be a problem as my current tooth structure after prep is healthy and adequate for Zirconia, and that any glue would work well because the tooth remaining is good. He says he will use glass ionomer, should I be concerned?

As well, I understand Dr. Gordon Christensen recommends cementing Zirconia with resin modified glass ionomer: https://www.dentaleconomics.com/art...nce-tech/cementing-zirconia-restorations.html
Do you argue otherwise?

Thanks again for your responses, I would greatly appreciate if you can clarify the above.

 

[honestdoc]

Sorry about the confusion. Glass ionomer bonds naturally to dentin (tooth) but not to zirconia. It is cemented mechanically similar to full gold crown is retained. Resin Modified Glass Ionomer is actually what I'm talking about. It is the modern GI that is reinforced for strength. Almost all modern GI products are actually RMGI and the non RM are being phased out.

Gordon Christensen has a lot of information and has his own testing and teaching facility. Unfortunately he has a lot of financial interests in many products so I usually do my homework further. The promising materials out there are bioactive such as Lime-Lite pulpal protectant, BioRoot root canal sealer, and Activa restorative materials.

I believe your dentist has your best interest. It is impressive how much you know as a non dental professional.

 

[Nan]

Sorry about the confusion. Glass ionomer bonds naturally to dentin (tooth) but not to zirconia. It is cemented mechanically similar to full gold crown is retained. Resin Modified Glass Ionomer is actually what I'm talking about. It is the modern GI that is reinforced for strength. Almost all modern GI products are actually RMGI and the non RM are being phased out.

Gordon Christensen has a lot of information and has his own testing and teaching facility. Unfortunately he has a lot of financial interests in many products so I usually do my homework further. The promising materials out there are bioactive such as Lime-Lite pulpal protectant, BioRoot root canal sealer, and Activa restorative materials.

I believe your dentist has your best interest. It is impressive how much you know as a non dental professional.

I understand and thank you. It's good to be informed.
What is your opinion regarding the ongoing release of fluoride from glass ionomer cements, because I am concerned secondary caries may develop due to excessive fluoride. I know the IAOMT recommends against dental materials containing fluoride.
Would you recommend any other alternative safe cements for Zirconia crown placement?
As well, would you recommend polishing or glazing the Zirconia crown?

 

[Nan]

Neither has biocompatibility problems. I simply prefer eMax as a all-round use material as it can be resin-bonded to preparations whereas zirconia can't be truly bonded without special preparations. In most cases where the retention is good, then even bonding is of secondary importance. Monolithic eMax (or zirconia) is stronger than layered eMax (or zirconia). There's really not that much difference between either for a back tooth. As for post and pins, the pins don't add much, but I have seen failures with simple cores that haven't been reinforced with at least one post. The biggest problems with posts is if they're too thick or long, then their usefulness diminishes, and the risks increase (been there, done that). I like to use one medium length post in largest canal, and a shorter and thinner post in a secondary canal.

I appreciate your insight. Is there an advantage to bonding crowns over luting them with cement? In other words; is eMax objectively preferred over Zirconia for the mere fact that it can be bonded?
My dentist says the remaining tooth structure is well sized and healthy, and therefore adhesion of Zirconia should be a non issue. Does that sound right?

 

[honestdoc]

I disagree with IAOMT's stance on being Fluoride free. I'm sorry I'm not able to help you with that. You may choose any system you want. For the record, my family and I have amalgam fillings (except my 3 kids with no fillings) and drink Fluoridated water with NO problems. I do have some opinions on amalgams but will not discuss it with IAOMT's beliefs.

 

[Nan]

I disagree with IAOMT's stance on being Fluoride free. I'm sorry I'm not able to help you with that. You may choose any system you want. For the record, my family and I have amalgam fillings (except my 3 kids with no fillings) and drink Fluoridated water with NO problems. I do have some opinions on amalgams but will not discuss it with IAOMT's beliefs.

I hear you.
Just another question re Zirconia crowns; I spoke with the technician that would be fabricating my crown, and I was under the impression all along that it would be monolithic Zirconia, but he told me that he the crown will be made of a KATANA Zirconia coping/core covered with CERMACO porcelain.
His reasoning being that such a crown would allow him to remove and add back material if needed, as opposed to monolithic Zirc - where if he removes he will not be able to add back.

I am truly confused at this point, as I understood all along that monolithic Zirc is much stronger for the posterior region, and I'm concerned about the Zirconia with porcelain.
From your experience with Zirconia crowns, what is your opinion and recommendation?

 

[honestdoc]

See if the technician can fabricate monlithic. The layering will weaken the restoration with the high likelyhood the porcelain may fracture off.

 

[MattKW]

See if the technician can fabricate monlithic. The layering will weaken the restoration with the high likelyhood the porcelain may fracture off.

Quite true, monolithic zirc or eMax is stronger than layered. But if your dentist has given you the choice of either material, then layered zirc should be OK, as he must have a relatively deep prep already (eMax require deeper prep than zirc).

 

[Nan]

Quite true, monolithic zirc or eMax is stronger than layered. But if your dentist has given you the choice of either material, then layered zirc should be OK, as he must have a relatively deep prep already (eMax require deeper prep than zirc).

My dentist actually explained that I have a big healthy molar remaining, and therefore I should not be worried about adhesion of Zirconia. He did prep it sub-gingival.
It was the technician who preferred zirc covered in porcelain, because he says he can easily "remove and add" material as opposed to monolithic - where he can only remove, not add back on. (I guess he's speaking about adjustment?)
Is that a good enough reason not to get monolithic? Or is it just the easy way out for a technician?

 

[honestdoc]

It's a tough call. Many times dental labs aren't equipped or technicians aren't trained for certain work. Maybe your dentist can send it to another lab for monolithic material of yours or your dentist's choice.

 

[Nan]

It's a tough call. Many times dental labs aren't equipped or technicians aren't trained for certain work. Maybe your dentist can send it to another lab for monolithic material of yours or your dentist's choice.

I spoke with my dentist, and he seems to agree with the the technician. He too recommends the layered Zirconia. He says it will be much more aesthetic and it won't be of lesser strength or fracture. He says the monolithic is going out of fashion.
But I am so confused, because that contradicts all that I read about monolithic and layered Zirc. I thought porcelain layered Zirc was conventional and problematic and that the monolithic was the newer solution in terms of fracture resistance.
It sounds like he is more comfortable using the layered, he says it should not fracture if it is made correctly, but I am still concerned that it may be the wrong choice after hearing multiple other dentists recommending monolithic for posterior teeth - as you have as well.
I don't normally grind or clench my teeth, and I don't suffer from bruxism, but I did have a deep cavity in that molar (upper first maxillary) that ended up with the root canal treatment - and I'm just so unclear about what to do now.
What is your opinion & suggestion?