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Delivery Tools for Better Impressions
Using an intra-oral syringe
Capturing an accurate impression is one of the most important ways that the dental team can communicate effectively with the laboratory. The assistant’s role in the impression-taking process can have a significant impact on the accuracy of the impression and can help make the difference between a perfect impression and a needed retake.
Although the assistant’s role in impression taking can vary by state, it is helpful for the assistant to be familiar with what makes a good impression in order to perfect applicable skills. The following is a list of characteristics that help assure an accurate impression1:
- The material mix should be uniform and homogeneous.
- The heavy-body and light-body materials should achieve a good blend.
- A rigid, sturdy impression tray should be used.
- The tray should be prepped with a thoroughly applied tray adhesive.
- The tray should be sufficiently filled with impression material.
- There should be no tray show-through of the impression material.
- The impression material and tray should have a strong bond.
- Teeth must not contact the tray.
- The captured margins should be detailed, with no tears or rough surfaces.
- There should be no voids or pulls on marginal detail.
- The dental team should provide the dental laboratory with complete information about the impression material that was utilized.
This list provides a good starting point for assistants to evaluate their impact on impression taking and examine how they might improve in any possible areas. The points relating to the material mix, marginal detail, and the interaction between heavy-body and light-body materials all relate in some ways to the proper use and application of wash material and heavy-body material. This article addresses the available tools that impact these four factors.
The Evolution of Material Dispensers
Some assistants may recall the days when light-body materials came in two different parts: hand-mixing on a mixing pad and then loading into a metal syringe. This technique was time-consuming, required significant cleanup, and carried a risk of improper mixing, which could ultimately result in the need for a retake.
The subsequently introduced delivery method—handgun cartridge dispensers—was a helpful step beyond the hand-mixing and loading technique. But as many dentists and dental assistants have experienced, these handgun dispensers come with their own drawbacks. Handgun dispensers are typically large, with a long disposable tip that is attached to the dispenser to direct the wash material around the prep in the patient’s mouth (Figure 1). The unwieldy size of these dispensers can sometimes compromise maneuverability in the mouth, leading to more work for the dental professional, who must confirm that wash material is adequately applied before seating the tray (Figure 2). On the patient side, the large gun can contribute to anxiety and sometimes cause patient discomfort when trying to maneuver the tip in the mouth.
In addition, control can sometimes be an issue with these dispensers, with the material dispensing in an irregular pattern. The plastic tips that come with most impression materials can occasionally have an irregular aperture or can even pop off the gun during dispensing. Some practices utilize autoclavable metal tips to avoid the unpredictability of the disposable plastic tips.
For many dental practices, a major annoyance with handgun dispensers is the amount of material waste involved in their use. Because the dispensing tip is so long, a considerable amount of material is left inside after an application, which must be disposed when the tip is thrown away. As dental practices monitor expenses for efficiencies, any product waste impacts the bottom line.
A final drawback of handgun impression material dispensers is the challenge that they present in infection control. One recent study found that during routine clinical use, impression guns can become contaminated with bacteria, including methicillin-resistant staphylococcus aureus (MRSA).2 The use of plastic impression gun covers and steam sterilization can help combat this issue, but this measure presents additional time-consuming tasks for the dental assistant.
A New Tool for Wash Delivery
A recently introduced alternative delivery system for wash material may help address many of these issues. The new Impregum™ and Imprint™ 3 Intra-oral syringes from 3M ESPE (www.3MESPE.com/syringe) are small, disposable plastic syringes that are suitable for use with any vinyl polysiloxane (VPS) or polyether wash material delivered from a 50-mL hand-dispensed cartridge. These syringes give the dental team member much better maneuverability in the mouth, allowing the operator to place wash material very precisely in the sulcus.
The two syringes are designed to accommodate the different mixing ratios of polyether and VPS impression materials, with the violet polyether syringe designed for a 2:1 mixing ratio (Figure 3) and the green VPS syringe designed for a 1:1 ratio. To load the syringe, the assistant simply removes the plunger and places the syringe on the openings of the handgun cartridge. The mixing tip should be left in a 90° position for this step. Holding the syringe firmly in place, the assistant uses the hand dispenser to fill it with the required amount of impression material (Figure 4 and Figure 5). The syringe is then removed from the handgun dispenser and the plunger is pushed in, with care taken not to push the paste into the mixing tip. If paste is extruded from the sides of the mixing tip joint during this step, it must be wiped off prior to application in the mouth. In the event that the two chambers of the syringe are loaded unevenly, the authors have found that the paste can be extruded from the joint in this manner deliberately (Figure 6). While not recommended by the manufacturer, this step can further minimize material waste.
To use the syringe, the mixing tip is folded out to a 180° angle and the plunger is pushed to extrude the paste. The paste should be extruded onto a mixing block until the base paste and catalyst are flowing in a homogenous mixture. The impression material can then be applied around the preparation(s) according to its instructions (Figure 7). After use, the syringe is disposed, eliminating the cleanup steps associated with use of the handgun.
A convenient feature of these syringes is that they can be kept for use for up to 12 hours after they are prepared. This gives the assistant the opportunity to consult the day’s schedule in the morning and prepare all the syringes necessary before beginning to see patients. The capacity of each syringe is sufficient for use on 2 to 4 preparations. With practice, the assistant can prepare for each case with a very precise amount of material in the syringe, further reducing material waste.
Better Impressions, Patient Comfort, and Material Savings
In terms of communicating with the laboratory and ensuring the best possible impression technique, intra-oral syringes can be a great help. Not only do they assist in gaining better access in hard-to-reach areas, but they can also help decrease the time between application of the wash material and insertion of the tray. After using a syringe, the dentist can quickly put it aside as the assistant hands over the filled tray. When using a handgun, this exchange can sometimes be awkward and can delay the seating of the tray, allowing more potential for saliva to seep or other problems to arise between the two layers of material.
Using an intra-oral syringe can impact not only the accuracy of the wash material application, but can also improve patient comfort. Because the syringe is dramatically smaller than a handgun, patients typically cannot see when it is being used in the mouth. In addition, the angle of the tip and its maneuverability can help the dental team pull less at the patient’s mouth and better accommodate patients who have difficulty opening their mouths widely.
Also, the compact size of the syringes helps dramatically reduce impression material waste, saving money for the practice. For practices that are concerned with the amount of money wasted by impression material left in handgun tips, they should be aware that comparatively the VPS syringe results in 67% less material waste, while the polyether syringe creates 84% less material waste.3
Making Life Easier for the Whole Team
Any tool that gives the dental team more control over delivery in the mouth—while at the same time enabling less ergonomic stress and making the process easier for patients—is a valuable one. Furthermore, with the ability to improve the quality of impressions and communication with the laboratory, use of the intra-oral syringe has the potential to make life easier for the entire dental team.
1. Making Better Impressions: EspertiseTM Troubleshooting Guide. St. Paul, MN: 3M ESPE; 2006.
2. Westergard EJ, Romito LM, Kowolik MJ, Palenik CJ. Controlling bacterial contamination of dental impression guns. J Am Dent Assoc. 2011;142(11):1269-1274.
3. Case study. Expertise: Experts News Source. June 2011:2.
About the Author
Thomas Trinker, DDS
Jennifer Rains, DA
Columbia, South Carolina