Abutment crown cement separation experience

[lcmlabforum]

Just a quick survey here, knowing there are so many combinations of factors that can impede that separation,
would everyone chime in on their personal protocol and experience with the following parameters?
1. Type of crown - PFM, eMax or Zirconia
2. Type of abutment - prefab (smooth),custom (esp. if prepared or roughened, or like Atlantis with horizontal grooves),or just Ti-Base.
3. Material of abutment - Titanium, gold, zirconia
4. Type of cement used (if known) - temp cement, Implant cement (Improv or Premier, etc),Zinc Phosphate, Relyx/resin modified glass ionomer (since they have acid that may cause more oxidation) or plain high strength cement like VarioLink or Panavia
5. If special treatment/bonding done - air-abrasion, HF etched intaglio of all ceramic crown.

Protocol:
Predrying time and temperature
How long in the oven and temperature
Any other significant steps, issues, and whether was successful

Thanks!
LCM

 

[gallagerdental]

Hi LCM: I'll give this a stab. My/labs background: 40 percent of our work is implant related. Been doing implant work 30 plus years. Thought you would need this as a barometer. That being said- PFM, emax and Zirconia, no reports of separation that I can recall, be it on a prefab, custom or cad. One thought on horizontal grooves, they have to be blocked out or have a spacer of some sort, during crown fabrication. For that reason I don't buy into the groove concept. I feel in time this could weaken the bond between cement and metal and or Zirconic. (Think of the old science trick, with two pieces of glass and water between them,you don't need a gap, just a thin smear of cement).What I do, do is cut one or more vertical grooves into the abutment as well as a flat surface, this gives the fit a more precise fit. As far as cements, the Drs. I work for use a variety of cements, mostly ones that are designed for this purpose. One in particular is the one made by Preat corporation . I believe it might be a silicone based product. As far as treatment- metal crowns are sandblasted prior to shipment. Metal, stock or custom have a rubbered surface. Zirconic as recommended. Hope this helps.


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[lcmlabforum]

Thanks, I was hoping to find out who have a fool-proof method to debond a cement retained crown in the lab for various reasons,
like shade change or adding a proximal contact.
There is at least one paper that found adding horizontal grooves manually will aid in retention, even after the fact/after casting,
for short crowns - as such, I anticipate those Atlantis abutments to be more difficult to remove.
!
LCM

 

[Rick Sonntag]

Not sure if my method is foolproof or not but it's worked for us:

Argen abutments with and without retention lines.
Zirconia crowns, both full zr and layered facial.
Panavia f 2.0
500ºC taken up over 20 mins, 40 min hold at temp to minimize oxidation of the titanium.
Analog and physical force still required to remove crown. Newtons of force required not available at this time.
Cement remains on abutment, very little if any on the crown.
Thankfully I don't have any demand for lithium dislilicate on implants in the posterior. Zero chance of successful removal with those.

 

[Brett Hansen CDT]

Here is the program we use to burn out cement on screw retained crowns:


I use a lot of Atlantis abutments. I really love their new custom bases for screw-retained crowns. We use Multilink cement from Ivoclar on our screw retained restorations. I don't think we have ever had one come off in the mouth. I have not had much luck removing emax from abutments without breaking the crown. All our screw retained restorations are zirconia now unless the doctor really wants emax. I don't have any problems separating zirconia crowns from abutments.

 

[gallagerdental]

Hi LCM- just checking in on thread- as far as the above mentioned thoughts, I do the same, for the removal, I run it up in the oven.Getting back to retention,I feel that horizontal grooves work well, but you still have to block out or relieve/ compensate for undercuts during fabrication of the crown. Also to allow room for cement. This leads to a gap, no matter how small. I was always taught that integrity was like water between two pieces of glass or if more of a space, prone to stress and ultimate loosening. . I have done cement retained crowns with a set screw that allows removal, if I wanted to make crown removable or for a definite lock. Hope this helps.


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[Andrew Priddy]

we bond with Panavia and debond at 400 C on a 5 min run.. will upload a pic soon
works with any Dr's cement I've run across, and keeps oxidation on ti low.. also been successful with e.max.
I have a hunch that the higher the heat, the more panavia expands, fracturing e.max.. the lab I moved to would debond at 500 with a low success rate on e.max, but as of now it's been a while since we had to do a full remake

we will typically do a medium wheel buff on ti abutments.. abutment design are squarish and somewhat parallel walls (works well for anti rotation as well as cement retention)

minimal spacer, no extra drill radius (not needed as our mills run fine detail)
we are also doing a lot more lingual set screws for some reason (3 in the last few weeks) Bredent has a nice system for that

 

[DanM]

I was at an implant course yesterday where the Dr said they're doing studies and finding that sandblasting the ti base before cementing is actually weakening the bond between the zi and ti for screw retained crowns. The shinny untouched surface with a bonder applied is resulting in higher bonding strengths. I sandblast them all and have yet to have a problem but if this is true even better. Has anyone heard anything about this?

 

[JohnWilson]

I was at an implant course yesterday where the Dr said they're doing studies and finding that sandblasting the ti base before cementing is actually weakening the bond between the zi and ti for screw retained crowns. The shinny untouched surface with a bonder applied is resulting in higher bonding strengths. I sandblast them all and have yet to have a problem but if this is true even better. Has anyone heard anything about this?

Interesting, would like to hear what bonder and scientific evidence this comes from. If its user obtained clinical observations I call BS, but like anything else I read on the net I always want to believe it

 

[Affinity]

It sounds illogical to think that unblasted metal would yield a stronger bond.. We dont do that with any other type of composite bond to metal, because Ive never seen a mfg. recommend that.

 

[CatamountRob]

I was at an implant course yesterday where the Dr said they're doing studies and finding that sandblasting the ti base before cementing is actually weakening the bond between the zi and ti for screw retained crowns. The shinny untouched surface with a bonder applied is resulting in higher bonding strengths. I sandblast them all and have yet to have a problem but if this is true even better. Has anyone heard anything about this?

Is there an issue with Ti bases de-bonding or is this someone looking for a problem where none exists?
I suspect the latter.

 

[Contraluz]

Protocol:
Predrying time and temperature
How long in the oven and temperature
Any other significant steps, issues, and whether was successful

Fortunately, I don't have to do it too often. But here is what I do:

I have a program with the pre-heat temperature set at 350 celsius (And I have gone as low as 300 celsius to do that). I let the restoration acclimate and then just keep the oven closed for 10-15 min. Most of the time this is enough to break down the cement. I then put the restoration on an analog, hold it with a hemostat, and with a little tapping you get them separated easaly. I don't want to go higher, do to unknown effects on the titanium (oxide) and the expansion of the different materials and a subsequent possibility of cracks...

Hope this helps,

Michael

 

[lcmlabforum]

Thank you all for your input. That low temp concept is interesting, and will try on that eMax. Implant turned before 35 Ncm, when the eMax bonded to zirconia abutment screw-retained crown was torqued down. That was even after progressive loading over 4 months, possibly 6. Sigh.
LCM

 

[subrisi]

I am trying to convince my customers to use it bases for their screw retained cases, but hey won't buy it. I always get the same answer that they debond in the mouth. I have no idea where they get this information and never heard any of my lab owner friends telling me they got a debonded crown back. I use metal primer on a sandblasted ti base and bond with multilink.
Can anyone paint me in the right direction to find out who spreads this information (Study?) and what is your experience in remakes? What is your cementing protocol? How long do you light cure?

 

[rkm rdt]

I've never had a base debond.

 

[Contraluz]

How long do you light cure?

I would not use a light cure cement for the ti bases! You most probably don't get enough light to the luting interface.

Use a specialized cement, like the one from Ivoclar: Multilink Hybrid abutment cement. It comes in MO and HO. I am sure there are others out there, too.

 

[rkm rdt]

I would not use a light cure cement for the ti bases! You most probably don't get enough light to the luting interface.

Use a specialized cement, like the one from Ivoclar: Multilink Hybrid abutment cement. It comes in MO and HO. I am sure there are others out there, too.

The HO has eliminated my need for a zirconia abutment with a few exceptions.

 

[subrisi]

I would not use a light cure cement for the ti bases! You most probably don't get enough light to the luting interface.

Use a specialized cement, like the one from Ivoclar: Multilink Hybrid abutment cement. It comes in MO and HO. I am sure there are others out there, too.

i use multilink, but I light cure it anyway

 

[Contraluz]

i use multilink, but I light cure it anyway

Are you using the dedicated abutment cement? See pic...

If so, I doubt it will have any effect. As long as you follow protocol, you should be save. As others have said, it holds up pretty well.

 

[SiKBOY]

Hi guys, I have an implant that is needing to de cement the crown from the abutment so the dentist can re insert the abutment and cement the existing crown back on .Somehow the screw has backed out on the cement retained crown so I have it all in one piece. I haev no idea what material the abutment is made from nor the crown. I'm guessing the crown is Emax. Its on a Straumman implant.

Is it safe to just bring it up to 400C and hold for 10 mins