One of the most challenging and frustrating procedures encountered in dental practice is impressioning for crowns, bridges, etc. Over the 35 years I’ve been practicing dentistry, I have changed, sophisticated, varied, and finessed my technique with all the tools available to me, and utilized most of the impression materials provided by a diversity of manufacturers. Until now, consistent success has been elusive.
Our goal, of course, is to produce a model such that, when a prosthesis is fabricated, it will fit the tooth and restore the dentition to ideal function with excellent aesthetics. To accomplish this, the preparation must follow the proper dictates, and the tissues duplicated as perfectly as possible.
Factors to be considered include:
(1) gaining access to the tissues to be impressioned;
(2) elimination of interfering fluids such as blood and saliva;
(3) introduction of the impression material into the periodontal sulcus;
(4) providing an accurate bite registration;
(5) reproducing the die so there is no distortion; and
(6) using a competent dental laboratory.
The purpose of this article is to discuss a technique that I have been using for several years that meets all of these criteria and does so in such a way that stress is removed from the procedure. This technique routinely accomplishes a dry field, more than adequate retraction, and accurately fitting dies. The important difference is that there is absolutely no hurry and no struggling with oral fluids.
TECHNIQUE
One of the components of crown and bridge impressions is to gain access to the dental sulcus when it is relatively dry and accessible to the impression material. The use of lasers, radiosurgery, or cord placement alone can provide success for this purpose. The following technique is another way that has worked for me and allowed me to eliminate stress when impressions are taken.
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| Figure 1. After tooth preparation. | Figure 2. Cord in place. |
The first step following preparation of the tooth or teeth is to place cord. It is likely that you will immediately react and say, “No…Not cord!” Indeed, I have used this technique successfully without cord, but I feel more comfortable with its use. The type of cord does not matter and depends on your preference (Figures 1 and 2).
The virtues of what I am discussing come into play because you can place the cord loosely, and there can be bleeding in the sulcus even after you have placed the cord. (Of course, having a healthy periodontium and atraumatic tooth preparation are always indicated and always make the impression procedure easier.) In those situations that are not ideal and there is some slight bleeding, this technique stops the bleeding and dries and opens the sulcus for the final introduction of the impression material.
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| Figure 3. Putty. | Figure 4. Putty in place. |
Next, a putty material is rolled and placed over the area to be duplicated, and the patient is instructed to close into a passive bite (Figure 3). The materials now available to you offer speed and ease of placement. (I use a vinyl polysiloxane material from Direct Dental Services called IS.) The putty is left for approximately 90 seconds. The patient then opens and the cord is removed (Figure 4).
A low-viscosity wash is then syringed into the sulcus, the putty (now set) is replaced, and the patient is instructed to bite again. This remains in place again for about 90 seconds. The matrix (putty and wash) can be removed after it sets and the field checked for dryness, or it can be irrigated and air dried at any time before taking the final impression. The putty-wash matrix can be replaced in position at any time (Figure 5).
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| Figure 5. Putty and wash. | Figure 6. Preparation after removing matrix. |
The putty and wash are removed and the preparation is checked. The field is almost always dry, and all bleeding has ceased, even in fairly resistant cases (Figure 6).
The impression can now be taken with no rush or urgency. For single crowns or small bridges, I like a triple tray technique. For larger cases, a full arch tray is indicated.
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| Figure 7. Final impression. |
I find that restorations returned by the lab fit more precisely when the impression technique consists of a soft tray material (monophase type) combined with the wash (Figure 7). When I used a “putty-wash” technique, my crowns seemed to fit too tightly. Perhaps there is a rebound when the impression is removed, and thus the dies are a fraction too small.
Choice of impression materials is strictly individual. Wonderful and manifold impression materials are available. One must find his or her own comfort level in viscosity and flow. Results in my hands are best when I use a polyether material such as Impregum (3M ESPE) or a polyvinyl siloxane material such as that provided by Direct Dental Services. The latter is a much faster and more pleasant tasting material.
CONCLUSION
A technique for making accurate impressions with a minimum of stress for the clinican has been described. Perhaps your first reaction is that this is a time-consuming process. With the fast-setting materials now available, I find that placing the cord through the final impression requires about 6 to 8 minutes. The utilization of this technique is so stress-free and accurate that time is made up when one doesn’t have to remake impressions. The practitioner is able to check the readiness of the field at any time, and when it comes time to make the final impression, the area is absolutely open and dry.
Dr. Polan maintains a full-time private practice in Huntington, NY. His research has been published in multiple specialty journals, and he lectures with CE certification at many dental societies. He can be reached at (631) 423-5533 or DrMpolan@aol.com, or visit
cosmetic-concepts.com.
