Index Impression: What Am I Doing Wrong?

posted in Restoration of Dental Implants

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Dr. M. asks:

When I pick up dental implant impression copings for a bridge, I use a custom acrylic tray with a small window where the impression coping screws poke through. I always do open tray impressions for dental implant bridges. I use either polyether heavy viscosity or bite registration material to pick up the impression copings. Usually everything fits just right. Occasionally the bridge will not fit exactly because the index is slightly off. I cannot figure this out. What am I doing wrong?

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8 Responses to “ Index Impression: What Am I Doing Wrong? ”

  • lapa May 7th, 2007

    Well,i asume it does not happen with single units?
    If so,there is still a slight movement between transfers when you take impressions for bridgework
    Now,what I do,is splinting the transfers with accrylic or anything which sets hard and does not
    interfere with impression material.Good luck.

  • JOnathan Abenaim May 8th, 2007

    Ok so we see that it does not happen on single units. Obviously because ther is way more give. With the bridge something is going wrong? Who is placing the analog in the impression coping? if its you are putting the impression down and the screwing it in or are you correctly holding it up with fingers on both ends of the coping and screw the analog in. Another reason as stated above is the movement of the copings. I always take closed tray and dont seem to have a problem. What types of abutments are you using? do you try in the abutments the the metal framework or go straight to finish. is the impression coping screwed in all the way. Do you take an xray? There are so many variables. Please post your exact procedure and system that you are using so that we can troubleshoot the problem.

  • Dennis May 8th, 2007

    Use a heavy bodied impression material and cover the screw all the way to the top. Place a little cotton in the screw hole so you can easily unscrew the post. This has always worked very well for me. Also make sure YOU hold
    the impression tray.

  • Bernardo Grobeisen May 8th, 2007

    I could think that you are using used copings and analogs , I recomened that you use new coping every time that you take the impression , this may sound expensive , but lab fees in remakes are more expensive , please let us know if you are using an internal or external conection.
    Best regards and hope you solve the problem.

  • ImplantPros May 8th, 2007

    My suggestion is that you use new impression copings every time and lute them together with something like GC Pattern Resin. As you, I prefer the open tray technique. Your problem may be that the impression copings may be binding with the tray thus when you unscrew them from the implant there is some movement or you are not loading the tray with enough impression material. Polysulfide is usually very stiff and will not allow any movement.

  • ed May 9th, 2007

    One very fast way to splint the impression copings before taking the impression is using conventional light cured composite material.

    I love not having to wait until it sets and distorion is virtually zero if you connect the implants incrementally.

    I usually place one big increment in each impression coping and then connect it with a small increment in the center.

    The bigger the implant case the lesser I worry about the cost of the composite.

  • Sheila May 9th, 2007

    Is the custom tray made with acrylic or composite? Acrylic can distort for days after it is made.

  • lapa May 11th, 2007

    I may agree with the comments sugesting to use new analogs evry time,could you explain whats wrong with a second hand transfer?

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