Open vs. Closed Tray Impressions?

The answer is yes.If you splint the transfers before taking impression on multiple implants case,you automatically avoid any possible movement between transfers,thus avoiding expensive remakes.

A custom open tray impression is the most accurate. DO NOT splint the impression copings as acrylic shrinks and will continue to shrink after the impression is removed from the mouth. In our laboratory we have had the best success with dentists who use this technique. Dr. Carl Misch teaches this proceedure at the Misch International Implant Institute.

Accuracy of 2 impression techniques for ITI implants International JOMI Volume 19 Number 4 2004 Please read and do not suggest that all systems fall under the same answer.

I have lectured on this topic and did an extensive lit review on studies to support my findings. To date I know of only one article that states closed tray to be more accurate than open tray techniques. Most are in favor of open tray techniques. An almost foolproof method is to take a prelim impression and then construct a rigid acrylic bar with gold cylinders on each implant. Try it in and verify the accuracy of your master impression. If it does not fit make very narrow cuts between the ill-fitting fixtures. Keep all the segments securely screwed in place and make sure they are not binding with each other. Join them with GC resin pattern or a compatible material. Let this cure and then pick this entire bar up inside an open tray impression with guide pins holding the segments in place. You now have a rigid intraorally confirmed acrylic verifying jig inside your impression. Pour it up and you will not have fit problems with your frameworks as long as the framework fits your new master cast.

I have been working with implants for over 25 years and have always taken an open tray impression. The only exception has been some of the "snap on" impression copings from ITI and 3i. In my office we take a preliminary impression in alginate and make 2 custom trays using a Triad unit. A hole (or holes) are put in the tray in the location of the impression copings. The trays are tried in with the copings in place to make sure the tray seats accurately and the coping doesn't interfere with the seating of the tray. In the case of mulitple copings which will be part of a bar or splint, I lute the impressions copings together with GC pattern resin. After placing the pattern resin, I leave the resin set for a minimum of 5 minutes and then take the impression. The lab pours up the model and returns the case as outlined by Dr. Boitet in a previous post. Has anyone tried light cured composite as a luting agent instead of GC Pattern Resin?

WE USE TRIAD LIGHT CURED COMPOSIT AT OUR LAB TO VERIFY MASTER CASTS BEFORE SENDING THEM TO BIOMET 3I FOR TITANIUM BAR CONSTRUCTION. THE RESULTS HAVE BEEN EXCELLENT AS THERE APPEARS TO BE VIRTUALLY NO SHRINKAGE OF THE MATERIAL. IF NECESSARY, THE UNIT CAN BE SECTIONED AND RECONNECTED IN THE MOUTH WITH THE SAME MATERIAL.

The article: Accuracy of 2 impression techniques for ITI implants International JOMI Volume 19 Number 4 2004 mentioned by RSS, does not really demonstrate that open and closed tray techniques are equally accurate. It merely demonstrates that the models based on different impression techniques using components will lead to inaccuracies. Just look at Table 1 within the publication. The AMM values represent the distances of the master model (= patient, unfortunately no SD given here, which would give us the accuracy of the measuring method, i would expect a SD of around 5 micrometres depending on the CMM - coordinate measuring machine). Compare this with the other values. E.g. distance 3 is approx. 400 to 1100 micrometres off! Standard Deviations (SDs) are up to 438 micrometres! A 95% confidence interval would even be bigger (not mentioned in this paper). The inaccuracies and SDs of the techniques used here are so big that you can't really compare the techniques. The authors even mentioned that within the publication. Within the discussion they say:"...the clinical relevance of these statistically significant differences is questionable and the application of these findings to clinical situations could be a complex task." I would have phrased it differently: Within our study the inaccuracies introduced by using an open or closed tray technique in combination with components were so big that we could not detect a difference between the techniques. That doesn't really mean that there is no difference or that ITI components are better than the components of any other manufacturer! As soon as we start using components (transfer posts, lab analogues, etc.) we introduce errors based on inherent component tolerances. These errors can be bigger than the errors introduced by impression materials and pouring models alone. The following paper is worth while reading: Kim S, et al. Displacement of implant components from impressions to definitive casts. Int J Oral Maxillofac Implants. 2006;21:747-55 All systems will have component tolerances since all the components are manufactured using milling machines. What we also know (and common sense already tells us that)is that repositioning components can lead to additional errors on top of the component errors. That is why the closed tray techniques are usually even more inaccurate than the open tray techniques. Final conclusion? Be aware that components introduce errors. Choose the prosthetic protocol wisely according to the clinical situation. And - there are other techniques than open/closed tray impressions using components! For more info I would reccomend a book by A. Sethi and myself: Sethi, Kaus: Practical implant dentistry, published by Quintessence.

All of the information already mentioned is great food for thought. Sometimes we overthink the problems and get into more trouble. If your lab wants open tray impressions, I would try a couple of cases that way and see if everyone is happier. The difference in labor is actually minimal. In my hands, using a closed tray technique depends on the design of the transfer coping and how acurately the coping can be placed back into the impression. When in doubt, I prefer an open tray impression.

We fabricate hundreds of implant restorations every month with the lions share of them being done with a closed tray technique. If the impression is taken with an impression material of a relatively high durometer rating the insuent impression will more than adequately preserve the position and there is no concern of disturbing the position when the analog is placed as this is done on the bench top instead of within the impression. We typically mark the orientation of the "flat" and seat the transfer back into the impression under the microscope to verify correct placement. Maybe you don't need a new technique maybe you just need a new lab. Make it SIMPL, it is truly better.

The decision to use an open or closed tray technique depends on the type of implant you are using. When using branemark type implants with an external hex, I splint the impression copings together with GC pattern resin. I do a bulk build up and then only after the bulk has set do I connect them. The connection should be a very thin space to minimize shrinkage of the acrylic. This works great and there is minimal soldering required. It uses an open tray technique. When using an implant that has an internal hex or similar connection, a splinted arrangement as presented previously will not draw and will not come out. This requires a closed tray technique followed by soldering similar to a previous post in this section.

On smaller cases a closed tray impression is great but for larger splinted together cases or bar over dentures I recommend an open tray impression. It is more accurate and when working on larger cases that accuracy is important.