My education concerning impression techniques for fixed prosthodontics was very similar to what is currently being taught in the vast majority of dental schools. The resultant hydraulic forces can cause a multitude of problems. A similar situation develops when an impression tray (b) containing a viscous impression material (c) is pushed onto a tooth preparation (a). Compressive hydraulic forces result as illustrated by the black arrows.įigure 2. A piston (a) is forced into a cylinder (b) containing a liquid (c). WHAT’S WRONG WITH “BULK COMPRESSION” METHODS?įigure 1. Also addressed are a few of the modifications and similar methods of which I have heard and seen in print, and I give my opinion as to why they will or will not yield acceptable results. This article presents a basic summary and rationale of the LIT, along with the complimentary principles of physical and biological behavior of elastomeric impression materials upon which it is based, so that it can be understood why the LIT is designed as it is and why it can do what it does. Other well-intentioned modifications contradict the original premise of the LIT by violating the precepts of viscous fluid dynamics upon which it was founded, and will invariably lead to results that fall short of the original technique. My observation is that some of these modifications are merely optional steps I have written or talked about in the past, and as such, are completely acceptable. I receive many calls and faxes from doctors who are confused about these modifications and seek my advice as to whether or not they are advisable. When using any dental technique, the temptation arises to modify it in an attempt to make it simpler and/or more effective. Since that time, I have been very gratified to observe the growing number of clinicians who are recognizing the benefits of this method and adopting it into their practices. After an in-depth study of viscous elastomeric impression materials and their behavior, I invented the laminar impression technique (LIT) in the mid 1970s.
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