All on 4: impression technique and denture fabrication?

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.



5 thoughts on: All on 4: impression technique and denture fabrication?

  1. Anon

    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.

  2. Ben says:

    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.

  3. Steve Hurst says:

    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.

  4. DrJ says:

    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

  5. Anonymous says:

    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

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