All on 4: impression technique and denture fabrication?

Authors

I have a few questions regarding the Nobel Biocare All-on-4:

1) After we convert a denture in the mouth and pick up the temporary cylinders in the denture, is it required to take an open tray impression, as well as provide information on the soft tissues to the lab (for final denture touch up) to make the denture intaglio surface convex?

2)Do you always advise converting the denture or do you also advise sometimes to just take open tray impressions after implant placement and let the lab make the denture from scratch after the implant placements?

3)Is the denture that is suggested, a fibre reinforced flexible denture or just a normal denture? Can a flexible denture be converted? I have my doubts as the acrylic will not adhere to the flexible material during immediate pick-up. That is the reason for the question.

8 Comments on All on 4: impression technique and denture fabrication?

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lee
9/20/2018
Hi! I've been lecturing on and restoring these All on 4 cases for over 10 years, so I'll give you the best info we've got. 1) Yes, you need to (ideally) do a reinforced open tray impression for the final when the case is ready to proceed to the last stages. You don't have to provide tissue thickness info, but it's alway appreciated. 2) There are two methods for converting after surgery, but both require a denture to already be fabricated. The direct method picks up the cylinders in the mouth, and the indirect method uses a post-surgical impression and picks up two cylinders in the mouth and the rest on the model. Some systems are using a modified indirect method that converts a denture wax up to a processed temp overnight, but this is an unnecessary step in my opinion. 3) We recommend against reinforced temps, and you should not try to use flexible materials. You're right that they would not adhere correctly.
Ben
9/20/2018
Your questions concern me that you have not actually been instructed on the process and protocol as this is fairly well documented and there are an abundance of books, publications, videos, etc. But to answer your questions simply. 1) An ideal immediate denture should be fabricated PRIOR to the surgery, and converted after the placement of the implants, abutments, temp. copings. (this can be an existing denture, but must be ideal for the provisional prosthesis. The impression for the final can be made in many ways, but you must accurately capture the implant-abutment positions and the final soft tissue profile. Yes, the entaglio surface must be flat or convex for clensability/maintenance. 2) Not certain I follow the question. You can elect to leave the implant submerged, give the patient a conventional denture and a final prosthesis after osseointegration OR you can fabricate a provisional prosthesis at the time of surgery. Both have merits and should be determined based on the individual patient and provider. 3) I would recommend ONLY using traditional acrylic, or a rigid frame-work. You are correct, acrylic does not bind to nylon (velplast/flexible denture). You are missing the fundimental concept behind implant integration success--> no micromovement. A flexable denture would be just that, flexable; I've never even thought to try it, so I guess I don't know, but I suspect this material would result in a pour prognosis of implant success.
Steve Hurst
9/21/2018
My practice is in San Diego. There’s a lab here that uses the PIC camera for full arch digital impressions. I’ve restored 5 full mouth cases using it and it’s the real deal. Passive fit on the first try. They also can mill a POM temporary, within 24-48 hours that is much stronger then PMMA if you have a patient who needs to wear a provisional for a longer period of time. Go to PICdental.com to see it in action. The lab is CAD dental. Kamil can explain how it works. I’m just a happy customer, I have no interest in either company.
DrJ
9/22/2018
My steps; Place implants Place MUAs Take blue moose impression of MUAs using stock tray Drill out holes where impression of MUAs are Place MUA impression copings join them together Take final impressions Now you have a model Do the same with denture with blue moose Place cylinders on MUAs on anterior , cut out windows in denture pick up with denture acrylic Place rubber dam over tissue Pick up front two Pick up back two on model
Anonymous
9/22/2018
Thank you dr J and dr Steve,Dr ben and dr anon for taking the time out to answer.Dr.J and dr anon my question is to you both.So what I do instead is that I place putty impression material over the healing caps(placed over mua s)and then place the denture over the putty and ask the patient to bite.so this makes marks on the putty which is now on the inside of the denture.This tells me where to make my 4 holes for pick up.And I pick it up(all 4 temp cylinders )in the mouth with acrylic.What is the advantage of picking up 2 in the mouth and 2 from the cast? Kind regards
Sheila
2/10/2019
I am a patient who has upper and lower acrylic All on Four with Nobel Biocare implants. After 2 1/2 years my upper teeth started breaking , the first four front teeth. I’ve kept getting it repaired and now my dentist/prosthodontist says my All on Four has failed and I need new dentures. She says my implants are good and my mouth very clean. Should I get acrylic or zirconium .
Anthony Sarlo DMD
6/23/2021
im curious as to the recomendation against "reinforced temps", can you expand on this ? as to the pick up of the cylinders in the full denture(immediate/provisional) you are using the temp cylinders to be screw retained onto the MUAs , correct? isnt that the same as a (framework)reinforced temp(PMMA, Radica etc) ? or are you expecting the tissue surface of denture(immediate/provisional) to help support the load? or are the cylinders in the denture, passively sitting on the implant-MUA? Thanks. A Sarlo
Lee Coursey
6/24/2021
When referring to "reinforced" temporary/provisional prosthesis we are usually assuming that some sort of rigid sub-structure has been added to the prosthetic in addition to the temporary cylinders and acrylic. Most likely this comes from a misunderstanding of the purpose of the temporary, as most of us are focused on prosthetic success. The purpose of the immediate load procedure is NOT to have the patient in a temporary, but to reduce the total time of treatment from extractions and placement to final restoration. The provisional actually promotes healing, distributing micro-movement across the entire arch. When you reinforce the temporary you change the whole scenario. Acting in such a way as to prioritize the prosthetic success of the temporary changes the use of the temp. Breakage in the temp during healing serves as a safety mechanism, protecting the implants during osseointegration. If we reinforce the temp we run a very real chance of negating any safety it provides.