There have been tons of articles and opinions on techniques and materials for impressions over the years, yet speak to any lab technician and #1 on the list of complaints about dentists is the one about "sloppy" impressions.
After inspecting a bunch of these in any given lab, you can easily understand why. The final impression is probably the most important starting point of any given case in the eyes of the lab technician, because many times it is the first contact they have with that particular patient. Most of the time, attention is solely paid to the physical appearance of the impression in hand, such as incomplete mixing of the materials, de-laminations, presence of blood and other fluids, and sometimes even the use of materials which don't match in properties or are even from different manufacturers (such as Impregum with a polyvinyl siloxane liner).
The physical appearance of the impression provides a preview to the technician of the difficulty or facility of the work to follow, and a notion of how the case in general will go. It also gives a distinct perception about the doctor from whom it originated.
After ditching a load of dies one day at a friend's lab (under a microscope and reimbursed with coal-fired pizza), I noticed that of the 30 dies I had in front of me, only two could be read to about 90 percent of the way around. All of the others required that I search for bur marks which could hopefully reveal the extension of the preparations. As you can imagine, tissue control was not present at all in these impressions. The thought of going to any dentist was suddenly once again a scary idea ...
My purpose here is not to shed some magic light on impression-taking or the materials involved. There are "many ways to skin a cat" as the saying goes, but with regard to taking good impressions, all you need is one good method that works for you. Your duty is to find the solution that fits your needs and does so consistently.
Try to keep in mind though that proper mixing, use of fresh materials, and working clean are critical to the results you will obtain. Always make sure to clean the debris from the teeth generated by preparation reduction and fluid migration.
The quality of a final impression's reproduction of the oral structures is obviously critical to the outcome of any case. But there is more to it than that. It is inherently the height of our communication with the lab ... the definitive form of tangible communication. One can ignore a written prescription or even a photograph, but an impression is central to the advancement of any lab procedures.
All too many times, issues are noticed only after models are poured. Issues which could have been addressed earlier had the case been evaluated and discussed by the restorative team rather than giving in to the constant urge to "just get the work done."
The identification of case challenges up-front allows for solutions to be found before actual procedures begin intra-orally. When a problem does occur during treatment (as can often happen), it will be smaller and easier to deal with. Rushing into any case and prematurely completing irreversible procedures without adequate study and thought can only serve to increase chances of difficulties or even failure of the proposed treatment.
So, what would your impression say? Would it tell of the time you spent reviewing all your case data? That you carefully thought things out? That you were careful and accurate with your technique? It is for you to decide ...
In the timeline of any proposed treatment, the impression demarcates the division of all of the thought, planning and effort that came before it as well as describes all of the available options possible as a result of it. Therefore, the timing of the taking of this impression is just as important as the detailed reproduction it should provide.
In the case of impressions, as in life, it is best to think before you speak.
Editor's note: This article was originally published in Spectrum Dialogue, May 2010.
Richard Gennaro, D.M.D.
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