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Impression Essentials

July 1, 2005
Learning to produce consistent, high-quality results may take effort, but if you are considerate of your impression material and technique, attention to details can make all the difference.

Learning to produce consistent, high-quality results may take effort, but if you are considerate of your impression material and technique, attention to details can make all the difference.

When it comes to impression materials, there are a number of important elements required to create high-quality results. First, you must have a clear understanding of the materials available and the differences between them. Variances in technique will probably dictate the type of impression material you prefer to use. Keep in mind that everyone’s technique is somewhat individualized, so it is important to determine what works best for you. One product may work well for a colleague, while another product performs much better in your hands. In any case, it also is important to understand the product you are using so it can effectively work for you.

A successful impression developed using 3M™ ESPE™ Permadyne™ Impression Material.
Click here to enlarge image

Today, advances in impression materials and delivery systems have resulted in a much less painful process for everyone involved, including dentists, assistants, laboratories, and patients.

Select the right material for you

As various impression materials have been introduced over the years, polyether and vinyl polysiloxane (VPS) have emerged as the clear favorites, comprising the majority of impressions.

First introduced in the mid-1960s, the innovative qualities of polyether impression materials have made them a popular choice because of their naturally hydrophilic consistency. Displacing moisture (blood, saliva, etc.) right from the start of the mix, polyether impression materials are well-suited for taking void-free impressions with superb reproduction of detail in moist conditions. My personal choice is 3M ESPE Impression Material. I have used this material for quite a long time, going back to the days when we had to mix by hand. In our practice, we use Permadyne anytime we have a large arch or full-mouth case, because the clarity of margins and exactness of detail are outstanding.

The other polyether impression material we use is the new 3M ESPE™ Penta Soft Quick Step Impression Material. Compared to conventional polyether materials, Impregum Penta Soft Quick Step Impression Material reduces the overall working time by at least one-third. The one-minute working time and the fast, three-minute intraoral setting save me a great deal of time. The material can be difficult to remove; however, we consistently achieve a better impression with clear margins using these two polyether impression materials.

In addition to polyether impression materials, I have also used DMG HonigumVPS impression material for a short time. From my experience with VPS, the material sets quickly, offers a more pleasing taste for the patient, and is quite easy to handle. VPS impression materials are typically not as rigid as polyethers and are more wax-like, so they flow well and can be easier to remove from the patient’s mouth. Although the ability of VPS materials to handle moisture has improved over the years, the true hydrophobic nature of this material continues to create difficulties in moist conditions. Any moisture, such as blood or saliva, will interfere with the accuracy of the impression. We often ended up with wrinkles in our VPS impressions, and neither my practice nor our laboratory believed we were achieving the clarity of margins that we did with polyether impression materials.

Where VPS may produce better results than polyether is with patients who have periodontally involved teeth with open embrasures. In these cases, polyether impression materials can lock into those areas and tear the impression when removing. It is worth trying other impression materials to determine which works best for you. Through my experience, I now know that polyether is a more exact, dependable impression material that works well for me. Accepting a slightly less desirable taste is worth the sacrifice to produce consistently impressive results.

Eliminate heavy lifting

Significant improvements in the delivery of both polyether and VPS impression materials over the past decade have simplified the impression-taking process.

Our office used to mix heavy body impression materials by hand with a spatula, which required a great deal of physical strain. The first time I hand-mixed, I thought to myself: Oh my, how do these poor assistants do it? Besides being physically challenging, hand-mixing was stressful because we were always worried about mixing the heavy body and light body materials at the same time.

Innovative delivery options now offer alternatives to the strain of hand-mixing. Many clinicians and their assistants now opt for automix systems such as the 3M ESPE Mixing Unit employed in my practice. The primary advantages of a mixing unit are a more consistent mix and less wasted impression material. It makes taking impressions very easy, and my assistants love it so much more than hand-mixing that we even keep a spare unit on hand.

Now when I take an impression, it is quick, easy, clean, and simple - much different than hand-mixing. We use the Pentamix mixing unit to mix the heavy body impression material while we put the mixing tip from the gun onto a syringe to dispense the light body material. The process works efficiently, and the unit itself is designed very nicely. It provides reliable dosing that is homogenous and void-free.

Pay close attention

When it comes to refining your impression-taking procedure, I recommend that you look into your options, test them for yourself, and use a product and process that best fit your needs. Learning to produce consistent, high-quality results may take effort, but if you are considerate of your impression material and technique, attention to details can make all the difference.

Quick Tips for Making a Good Impression

Clean, rinse, and dry the preparation very well. Preimpression techniques are just as important as the impression material you select. Be careful of latex and hemostatic agents, which can easily ruin a good impression.

Evaluate the margins. Ensure that you can see all of your margins and that they have been thoroughly cleaned or rinsed and dried very well to ensure excellent retraction.

Check impression trays for proper fit. A good tray will offer stability and be comfortable for the patient. Check to make sure the patient can bite down properly, as an improper bite can create an inaccurate impression.

Evaluate the height of the palatal vault to determine the necessary amount of impression material and minimize flow.

Finally, go back to the basics. Regardless of which type of impression material is chosen, it is important to realize that continued success is only possible through proper clinical technique and correct use of the material.

Amanda Canto, DDS
Dr. Canto, founder of Cosmetic Dentists of Houston, received her undergraduate degree from Southwestern University in Georgetown, Texas, and obtained her DDS from the University of Texas Dental Branch in Houston. An international lecturer, she serves as an expert source in cosmetic dentistry for various news agencies.