July/August 2009, Volume 5, Issue 7
Published by AEGIS Communications
New Polyether Dispensing Method, Same Polyether Accuracy
Robert C. Margeas, DDS
Consistently taking an accurate impression is one of the most challenging daily tasks in a dental office. Choosing the appropriate material for the task at hand adds an additional hurdle, as both polyether and polyvinyl siloxane (VPS) materials offer different characteristics and delivery options. Flexibility in an impression material is, therefore, a welcome innovation.
While we know that polyether materials are set apart by their hydrophilicity, flow properties, and forgiving setting behavior, these materials have previously been limited to dispensing from an automatic mixer, or after mixing by hand. Recently, however, 3M ESPE (St. Paul, MN) has introduced its well-known Impregum™ Soft Polyether impression material in a cartridge dispenser, making it the first polyether to offer this mode of delivery.
Many dentists are familiar with the characteristics of Impregum after having used it in the Pentamix™ line of mixers for many years. However, dentists who did not have room in the operatory for a Pentamix machine, or who did not want to make the investment in the machine, had to face the choice of either hand-mixing their polyether, or using an alternative material. This new cartridge delivery system is an exciting breakthrough for dentists who want more options for polyether mixing and dispensing. Now we can have both the clinical benefits of a polyether impression material and the convenient dispensing style of a VPS. Additionally, its portability means the material can easily be used in multiple operatories. There is now no significant expense to prevent making polyether readily available in all of a practice’s operatories. A review of the material’s helpful clinical characteristics demonstrates why this breakthrough could be a major boon to many dental practices.
Hydrophilicity is often cited as one of the key clinical benefits ofpolyether materials. Impregum Soft impression material is moisture tolerant by nature, meaning that during its entire working and setting time, moisture in the mouth will not get in the way of taking an accurate, void-free impression. In contrast, VPS impression materials are actually water repellent, and thus surfactants are added to them to increase hydrophilicity. However, when a surfactant comes into contact with moisture, it then has to travel to the surface. The additional time needed for this chemical process effectively slows the VPS material’s hydrophilicity, preventing it from completely developing during working and setting times. This delay can ultimately result in voids and inaccurate impressions. The difference in hydrophilicity between polyether and VPS impression materials has been demonstrated in studies measuring the contact angles of water droplets on each material. The polyether in these studies regularly shows greater hydrophilicity.1
Many dentists prefer polyether to VPS impression material because of itsflow properties, which help the material reachcritical areas without exerting high pressure(useful in cases of a deep sulcus or undercut areas). Flow properties areoften demonstrated via a “shark fin” test, in which the material is injected into a small receptacle, over which a fin-shaped mold and a weight representing the pressure applied during clinical use are placed. The weight is allowed to sink slowly into the material, and after the setting time has passed, the height of the “fin” is measured, with a taller fin demonstrating better flow properties. Impregum Soft impression material has performed well in this test in the past, with results showing that it exhibited significantly better flow properties than VPS materials, both at the beginning and the end of the working time, and with its flow properties remaining almost constant throughout the entire working time.2
New research was conducted on the cartridge-dispensed material to add to these findings, with researchers comparing the flow of Impregum Soft polyether tray impression material delivered from the hand dispenser against commercial VPS impression materials. The previous findings were bolstered with this study as well, which found that the Impregum material again exhibited higher flow than the VPS tested. 3
An additional unique feature of polyether is its “snap-set” behavior, which means that the material will not start setting until the end of the working time, and then does so immediately. This characteristic helps polyether deliver excellent detail without distortion, using a variety of impressioning techniques. This forgiving behavior of the material is just one morequality that sets it apart from VPS.
These helpful clinical qualities can help dentists to ensure the consistent capture of detailed, highly accurate, and undistorted impressions, as demonstrated by the following case.
A 55-year-old patient presented to the office for treatment of herupper anterior teeth. She was not happy withher esthetics, and also complained ofsensitivity. The left central, lateral, andcuspid exhibited wear and erosion on thelingual (Figure 1 and Figure 2). Thepatient wanted theanterior teeth to match and requested crowns on the upper leftanteriors.
The teeth were prepared for full-coverage Lava™ (3M ESPE) restorations. Once the teeth were prepared, retraction cord (Ultrapak #000, Ultradent Products) was placed to displace the tissue and gain access to the margins (Figure 3). Two cords were used in this technique, with the second cord placed over the first, and the first cord left in place during the impression. To make the impression, the top cord was removed and Impregum light-body impression material was injected into the sulcus (Figure 4). As the light-body material was injected around the preparations, the tray was filled using Impregum Soft impression material (Figure 5). The tray was placed in the patient’s mouth and held steady for 4 minutes (Figure 6). The tray was then removed and inspected, exhibiting a beautiful impression (Figure 7 and Figure 8).
The unique properties of Impregum Soft Polyether impression material combine to make it an excellent choice for taking accurate impressions, using either the one-step heavy-body/light-body technique, or the monophase technique. The ultimate goal of making a great impression, of course, is creating a well-fitting restoration. By using proper technique and a high-quality impression material like Impregum Soft impression material, dentists can realize the benefits of reduced retakes, remakes, and adjustments, helping to both satisfypatients and keep the practice running efficiently.
1. Klettke TH, Kuppermann B, Führer C, Richter B. “Hydrophilicity of Precision Impression Materials During Working Time,” CED/IADR, Istanbul, 2004,submitted for publication.
2. 3M ESPE Impression Materials Update. Studies show clinical advantages in using innovative “Soft” polyether vs. vinyl polysiloxane. 2004.
3. Durack JL, Hudson C, Kuppermann B, Klettke T. Flow of Impression Materials During Working Time. Espertise™ Scientific Facts 2008. IADR #3191 (2008).
About the Authors
Robert C. Margeas, DDS
Department of Operative Dentistry
University of Iowa College of Dentistry
Iowa City, Iowa
Des Moines, Iowa