Inside Dental Assisting
Jan/Feb 2009, Volume 5, Issue 2
Published by AEGIS Communications
Capitalizing on the Advantages of Alginate Alternatives
Hollie A. Bryant, DA II; Jeff T. Blank, DMD
It’s early during the work day, and your busy practice is running on all cylinders. You have two hygiene rooms hitting their production goals and double-booked operatories for the dentist; however, the laboratory area has a big problem. Four alginate impressions lie wrapped in wet paper towels waiting to be poured, and no one has the time to do it. With every minute that passes, dimensional stability, tear resistance, and accuracy decline, and before you know it, the impressions may be rendered useless. If so, the retakes are costly, embarrassing, and inconvenient to your patients.
Problems with Conventional Alginate Materials
While conventional alginate (irreversible hydrocolloid) still remains an effective, predictable, and popular impression material, the physical properties and working characteristics are extremely technique-sensitive. Exact powder/water ratios are easily abused, and erratic mixing can lead to errors in flow, dimensional stability, and tear strength in the mouth. Because alginate materials contain water, they are highly subject to evaporation over time and must be poured immediately to be accurate. This requires offices to have laboratories equipped with dental stone and the workspace to pour impressions. Further frustration can come from not removing the stone casts from the alginate while they are hydrated, resulting in model fracture. Re-pours are almost impossible.
Even though dentists and assistants know of alginate limitations, they may not know that some companies now offer alginate alternatives, products designed specifically to counter the negative attributes of alginate materials. One such product is Silginat® (Kettenbach LP, Huntington Beach, CA). Silginat is a medium-viscosity, addition-curing, elastomeric polyvinyl siloxane material design for making anatomic impressions. Other products include AlgiNot™ (Kerr Corp, Orange, CA) and StatusBlue® (Zenith/DMG Brand Division, Foremost Dental LLC, Englewood, NJ).
Alternatives to Alginate
Alginate alternatives have distinct clinical advantages that are recognized easily by both dentists and assistants. Most of these materials can be dispensed in both dual-barrel mixing cartridges and foil-bag magnums that are compatible with Pentamix™ 2 machines (3M ESPE, St. Paul, MN). For Silginat users, Kettenbach LP offers a streamlined bulk dispenser (Plug and Press® automatic dispenser) that takes up less counter space and guarantees the correct mixing speed and ratios (Figure 1). Silginat is also available in 38-mL cartridges using standard 1:1 hand-held extrusion guns. As many assistants know, mixing machines eliminate mixing bowls, spatulas, and the mess associated with traditional alginate preparation.
The indications for using alginate alternatives are numerous. These materials can be used to create anatomical models, opposing models in crown-and-bridge procedures, impressions for fabrication of removable prosthetic restorations, impressions for orthodontic work, study models, and models used to fabricate splints. Most alginate alternatives offer convenient setting characteristics for both assistants and patients, including reduced mess and waste. And for Silginat users, the material has a total working time of 1 minute, 30 seconds, and a unique thixotropic consistency that flows under pressure but does not run spontaneously into the pharyngeal cavity.
Because these materials create polyvinyl siloxane impressions, they do not have to be poured immediately and can be recast if duplicate models need to be made. However, if desired, the impressions can be poured immediately with no waiting period. For Silginat users, its medium-body viscosity not only makes removal from the mouth easy (even with orthodontic appliances), but also makes removal from the stone model easy, which helps to reduce the number of fractured models.
Silginat can be used to make preoperative models or opposing arch impressions. First, dispense the material into a disposable impression tray (Figure 2). Simply load the foil bags into the cartridge body, place the cartridge body in the Plug and Press automatic dispenser (or comparable unit, ie, Pentamix 2), attach the supplied mixing tip, and press the button. The mixing ratio is always accurate, and the medium-bodied viscosity stacks nicely into the tray without being runny, which allows it to stay in place when the tray is turned upside down for a mandibular impression (Figure 3). The start-to-finish set time for Silginat is 2 minutes, 30 seconds, to 3 minutes (depending on which delivery system is used). This proves to be adequate time for mixing, and reduces the time in the mouth, which pleases most patients. After mixing, put the tray into place. The material will displace the cheek and tongue, to allow capture of important aspects of the oral anatomy (Figure 4).
Silginat was designed to be easy to remove from the mouth, rigid enough to be extremely accurate, and flexible enough to be used for orthodontic impressions. Figure 5 shows the final impression. Because Silginat is dispensed from a vacuum-filled foil pouch or cartridge, air bubbles are rare. The material flows nicely into the buccal vestibule and sublingual spaces and captures the retromolar pad. These handling and flow properties make Silginat suitable for impressions for removable prosthetic restorations.
The material also can be used to create impressions for the fabrication of temporary crowns and bridges. Simply load a quadrant tray (Figure 6) and capture a preliminary impression of the teeth to be restored, and then set it aside. After the teeth are prepared, place a desensitizing agent (ie, Gluma®, Heraeus Kulzer Inc, Armonk, NY), load the preliminary Silginat impression with bis-Acrylic provisional material (Figure 7), and reseat the impression in the mouth (Figure 8). After the occlusion is adjusted, trim and polish the inlay temporaries in the mouth (Figure 9).
Silginat polyvinyl siloxane impression material is an alginate alternative that can be used in any application that conventional alginate materials are used. With the distinct advantages of being easy to dispense, providing bubble-free mixes, handling ideally, offering adequate working times in the mouth, displacing soft tissue correctly, setting in 1 minute, 30 seconds intraorally, and creating accurate impressions, along with the ability to be poured and re-poured long after the patient is gone, Silginat should be considered by all assistants looking to lessen the chaos of their offices’ laboratory areas.
About the Authors
Hollie A. Bryant, DA II
Editorial Board Member
Inside Dental Assisting
Carolina Smile Center
Ft. Mill, South Carolina
Jeff T. Blank, DMD
Carolina Smile Center
Ft. Mill, South Carolina