Impression Materials

Written by Dentistry Today Thursday, 02 June 2011 17:39

PRODUCT FOCUS
• Impression Materials •

George Freedman, DDS

The process of taking impressions is simply to transfer 3-D physical data from the patient's mouth to the stone model—as accurately as possible and as comfortably as possible. The greater the transfer accuracy, the better the crown or bridge will fit, and the less time needed for chairside adjustment. This is not a major clinical concern until the practitioner realizes that chairside time costs $6 to $8 per minute.
As a major complicating factor, the mouth is a very wet environment. The laboratory bench, however, is a very dry environment. The impression material must be able to replicate hard- and soft-tissue structures under both conditions with minimal hygroscopic distortion. In addition, the dental laboratory may be remote from the practice, thus impressions are transported under varying unpredictable conditions of temperature and air pressure across town or across the continent. The impression material must be immune to these variables.
Impression materials are used with a wide range of clinical techniques; they all require simplified techniques, excellent predictability, and great latitude of clinical application. Most practitioners do not have the time to address the science and technology that goes into the development of a successful impression material, the behind-the-scenes work that facilitates and speed's chairside procedures. In fact, the many impression technology advances of the past 25 years are easy to forget. Rubber base (slow setting and foul smelling) was the most common and best available material into the mid 1970s. In the late 1970s, hydrophobic polyvinyl impression materials were introduced, gaining popularity. They are the most commonly used impression materials in North America. In the mid 1990s, truly hydrophilic polyvinyls that could take accurate impressions of wet intraoral surfaces were introduced. Other enhancements included material strength, tear-resistance, repeated pourability, and easy-to-read coloration.
The ideal impression material reflects all the hard- and soft-tissue details, including their static relationship, in the mouth. This data is transferred during the relatively short working time (30 to 90 seconds) and fixed (polymerized) into the impression material memory during the setting time (60 to 240 seconds). The shape of the impression is unalterable after this. Impressions must work perfectly the first time, every time. The importance of making the first impression count cannot be overstated. The cost of retaking an impression includes not only materials such as trays, impression materials, etc., but also chair time. All told, retaking an impression can easily cost between $50 to $100 and more. Thus, the selection of the most appropriate impression material for the job is essential.
Vinyl polysiloxane impression materials are accurate, fast, predictable, and, last but not least, easy-to-use. The range of available materials offers various properties and specifications that suit every procedure and every practitioner. The following guide identifies some of the selection criteria that can be used by the dentist in determining which impression materials are most appropriate to the task at hand.

Mixing technique
An auto-mixing, dual-barrel syringe may cost somewhat more than spatulating extruded components on a pad, (and involve disposable components) but the increased ease and predictability of impression taking are well worth it. Cartridge auto-mixing provides a precise base/catalyst proportion, and a rapid, single-handed, bubble-free delivery directly onto the prepared tooth. Electrically powered mixing devices have the added advantage of eliminating the requirement for manual strength on the impression trigger. These are larger devices, and have a greater footprint in the operatory, however. Pad spatulation is severely limited by inaccurately dispensed component amounts, a technique-sensitive manual mixing process that often incorporates air bubbles, and inefficient syringe and tray loading. Manual pad spatulation should be avoided whenever possible.

Setting time
Faster setting impression materials are very advantageous in the efficient practice. It is essential that the faster setting not compromise the impression quality by any means. Faster setting times are convenient for both patient and dentist, particularly when only one or 2 teeth have been prepared; decreased intraoral tray time is easier for the patient, and saves chairside minutes for the dentist (each chairside-dentist minute costs $6 to $8). In most practices, faster-setting impression materials and 3 minutes start-finish are used for quadrant- or triple-tray impressions. Regular set times (5 to 6 minutes) are more suited to full arch and multiple-abutment impressions. The practitioner first selects the required working time for positioning the impression material onto all the prepared teeth, and then chooses the appropriate setting time.

Contaminants
Many polyvinyl materials (A silicones) are prevented from polymerizing by certain commonly used dental materials. The most common contaminant is trace sulfur (found in latex gloves) that interferes with polyvinyl polymerization, preventing complete setting. Glove lubricating powders also contain trace components of contaminating chemicals. You should avoid touching impression materials with gloves.
Eugenol materials, common in provisional cements, liners, and bases, can also inhibit polyvinyl setting. Acrylic provisional crown materials contain amines that also interfere with polymerization. Some hemostatic agents used with cord retraction may be chemically incompatible with impression catalysts, and should be washed away thoroughly, even though some polymerizationinhibiting will undoubtedly remain.

Hydrophilic versus hydrophobic
The mouth is always wet. VPS impression materials are inherently hydrophobic but can be chemically altered to make them hydrophobic. Newer impression materials are designed specifically to work in a wet environment. These are far easier and better to use.

Viscosities
Impression techniques may call for different viscosities. The clinical choice of impression material may depend on the range of viscosities in an impression line. It is essential that these varying viscosities all have the same rheology, or chemical characteristics, that are typically manufactured into product lines. It is generally not a good idea to mix components from different manufacturers into the same impression.

Flavoring
Current impression materials are either taste- or odor-neutral, or pleasantly flavored. While the patient may enjoy the experience, the flavoring chemicals often increase salivary flow during the impression taking, complicating the process unnecessarily.

Pour time
Some impression materials require a dwell or maturation time prior to the stone pour, while others can be poured immediately. You should check the instruction manual. Chairside inlay techniques, for example, require immediate pourability.
Since the impression may be sent to a distant dental laboratory, a longer pouring time is important. The impression may not reach the lab until one or 2 days after mouth removal. Typically, most newer impression materials allow for a minimum of one week.

Shelf life
Similarly to other dental materials, impression materials do not last forever. You should check the expiration date on the cartridge. Use materials prior to their expiration for best results. Some materials have shorter shelf lives. Office stock should be determined by the expected utilization rate. While impression materials in bulk cost less, they become more expensive if half the stock must be thrown out due to expiration.

Ivoclar Vivadent

Virtual impression materials combine the most desirable attributes of vinyl polysiloxane materials into one system. Available in fast and regular setting times, the system features 3 viscosities of wash material (x-light body, light-body, and medium-body), a high viscosity tray material (heavy body), putty, and a monophase material. The monophase and heavy-body materials are available in 50- and 380-mL cartridges. For more information, call (800) 533-6825 in the United States, (800) 263-8182 in Canada, or visit ivoclarvivadent.com.

3M ESPE

Impregum Soft Polyether impression material provides polyether benefits and convenient vinyl polysiloxane dispensing style, allowing use among multiple operatories. Its hydrophilicity allows for superb impressions in moist conditions and its flow properties offer excellent precision and accuracy of fit. 3M ESPE will soon introduce the state-of-the-art Impregum Single-Use Intraoral Syringes—a new, easy-to-use delivery system. For more information, call (800) 634-2249 or visit the Web site 3mespe.com/greatimpressions.

Danville Materials

Danville vinyl polysiloxane materials are accurate and have exceptional tear strength and stability. The high fluidity and hydrophilicity assures excellent results. The impression materials have also received a REALITY 4 star rating. Danville offers 1.5 minutes for First Quarter, 2.5 minutes for First Half, and 4.5 minutes for Star VPS. First Quarter and First Half Monophase are also ideal for provisional impressions. For more information, call (800) 827-7940 or visit danvillematerials.com.

Exacta Dental Direct

FRESH Bold VPS is an advanced vinyl polysiloxane impression material system that provides dentists with incredible ease of use. It is available in 8 viscosities and 2 setting times. The lower viscosities have exceptional hydrophilic properties. For more information, call (800) 474-7665 or visit exactadental.com.

GC America

EXA'lence is the new generation of vinyl polyether silicone impression material. It is intrinsically hydrophilic with optimal flow and high tear strength, the result being a predictable performance under any clinical environment. EXA'lence will satisfy dentists, lab technicians, and patients with easy handling, maximizing comfort while providing excellent results. For more information, call (800) 323-7063 or visit the Web site gcamerica.com.

DMG America

Honigum impression materials capture incredible detail every time. The secret to its superior detail lies in its unique chemistry. It is a hydrophilic vinyl polysiloxane impression material with a patented microcrystalline wax matrix that lowers its viscosity under bite pressure to flow into the most difficult to reach subgingival areas. It also has a "snap set" that prevents distortion, yet is easily removable. Honigum's pleasant honey aroma and neutral taste also help to make the material extremely patient-friendly.

StatusBlue is an alginate replacement material that has a firm consistency for slump-free tray dispensing, sets quickly for greater patient comfort, and stays dimensionally stable. It is the faster and easier alternative to alginates for creating situation impressions for temporaries, model-cast dentures, orthodontic models, and opposing jaw models. The unique viscosity allows it to flow better under bite pressure.

For more information, call (800) 662-6383 or visit dmg-america.com.

Trident Dental Laboratories

Tri-Vinyl vinyl polysiloxane impression material delivers accurate results, ease of use, and the quality expected. It is odorless, tasteless, and can be immersed into disinfectants. Available in a variety of viscosities and set times, it also provides the dimensional stability and tear resistance needed to maintain the impression's integrity, no matter what technique is used. For more information, call (800) 221-4831.

Zhermack

Colorise VPS impression material takes advantage of Zhermack's patented Chromatime technology. This innovation in impression material employs color change to signal the time required for impression taking. There's no need to watch the clock and no guessing when the impression is done. With an extremely low contact angle, it actively interacts on the oral fluids, allowing the material to flow in the gingival sulcus.

Elite HD+ is a unique impression material that combines nanotechnology and hydrophilia to guarantee the highest levels of performance. The application of nanoparticles allows it to reach an ideal level of flowability within the gingival sulcus. Allowing hydrophilic behavior after just 2 seconds drastically reduces the risk of bubble formation. For more information, call (877) 819-6206 or visit zhermackusa.com.

Heraeus Kulzer

Flexitime is the vinyl polysiloxane material that consistently provides precise detail for an accurate marginal fit. It offers superior hydrophilicity on a polyether level for excellent performance in moist environments. Additionally, its exceptional toughness prevents tears and distortion upon removal. Even in the most adverse conditions, it offers reliable impressions. Also, fast-setting Flexitime Xtreme is perfectly suited to your more common single-unit impressions. For more information, call (877) 258-5937 or visit heraeus-flexitime.com.

Glidewell Direct

The Capture Impression System is an ultrahydrophilic vinyl polysiloxane formulation. It is available in 7 viscosities and 2 oral set times for crown and bridge impressions. The contrasting colors of the light and medium to heavy or putty viscosities provide quick visual inspection of the marginal detail. Hard bite is used for standard bite registrations and transparent clear bite is ideal for the fabrication of a scan index for CBCT scans. For more information, call (888) 303-6470 or visit glidewelldental.com.

Kerr

Kerr continues to deliver an alginate alternative with outstanding value and clinical performance—now in a faster set time to increase patient comfort without sacrificing working time, plus an improved thixotropic consistency. AlgiNot FS is ideal for preliminary impressions, provisional impressions, orthodontic models, bite registration, sports guards, bleaching trays, and more.

Extrude is a vinyl polysiloxane impression system available in 4 viscosities. Extra is a thixotropic, nonslumping tray material that minimizes distortion while providing a flexible-firm set that promotes easy tray and die removal. Medium provides excellent flow as well as sufficient body for use as a tray material. Wash is a very low viscosity and is used in conjunction with Putty or with Extrude Extra for certain techniques. MPV is a unique material that can be used for both the tray and syringe material.

Take 1 Advanced vinyl polysiloxane impression material employs Kerr's long history of expertise in developing high-performance impression materials, along with recent technological advancements, to deliver a VPS material with the optimal combination of physical properties: strength, elasticity, dimensional stability, and the ability to register detail in any environment. It comes in the widest selection of set times, delivery systems, and consistencies available on the market today.

For more information, call (800) 537-7123.

Kettenbach LP

Identium has a new chemistry for one-step impression technique. It is offered in 3 viscosities—medium, heavy, and light. Identium Medium is intended for implants and fixed impressions but is also suitable for crowns, bridges, inlays, onlays, and veneers fabrication. Identium Heavy is used for the fabrication of crowns, bridges, inlays, onlays, veneers, removable dentures, and implants.

Panasil is a line of addition-curing silicone final impression materials. It can be used for one- or 2-step crown and bridge impression techniques. It is available in a 50-mL cartridge and 362-mL foil bag for the Sympress dispenser.

For more information, call (877) KEBA-123 (532-2123), visit kettenbach.com, or e-mail This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

DENTSPLY Caulk

Aquasil Ultra Smart Wetting Impression Material is known best for its unique combination of high tear strength and very low contact angle. You can use it with B4 Pre-Impression Surface Optimizer for excellent detail with less stress. A complete portfolio of 5 tray and 3 wash material viscosities are available in 3 set time options. Delivery systems include the digit Targeted Delivery System, which is a unidose system for easy wash material application, in 50- and 380-mL cartridges. For more information, call (800) 532-2855 or visit aquasilultra.com.

J. Morita USA

PerfectIM Systems offers accurate final impressions of subgingival margins without use of a retraction cord, gingival excision, or application of hemostatic agents. This 2-step, vinyl polysiloxane impression system eliminates the time-consuming task of packing a retraction cord. These materials are cartridge-dispensed, radiopaque, hydrophobic, thixotropic (except SnoWhite), tasteless, and odorless. For more information, call (888) JMORITA (566-7482).

CLINICIAN'S CHOICE

AFFINITY hydroactive impression material is customized to your procedure pace and features third-generation chemistry to give you unparalleled dimensional stability for extreme accuracy, improved hydrophilicity, and maximum tear strength. Independent working and set times allow you to work at your own pace. For more information, call (800) 265-3444 or visit clinicianschoice.com.

Discus Dental

Precision is a premium vinyl polysiloxane impression material with amazing detail reproduction, making it the material for the most discerning clinicians. Its revolutionary formula displaces moisture better than other VPS materials, creating detailed margins in even the most challenging situations. You can make perfectly fitting crowns with one impression. Precision's flexible working time offers a completely set impression within 2 minutes and 45 seconds to 3:45.

Splash is the impression material for the clinician who demands reliability and value in a vinyl polysiloxane impression material. It features excellent flow properties, exceptional tear strength, and a delicious wild berry scent that patients will love. It is available in 2 set times, 5 high-contrast viscosities, and 4 delivery methods. For more information, call (800) 422-9448.

DUX Dental

Winner of the 2010 Dental Assistants Award from THE DENTAL ADVISOR, Kromafaze is a dust-free, color-changing alginate that maintains stability for up to 100 hours. It changes from purple (for mixing) to pink (for loading) to white (for removing) to signal each step. It's available in one-lb canisters/bags and also as a single where the water measure and alginate are part of the packaging. For more information, call (800) 833-8267 or visit duxdental.com.

Parkell

SHARP premium vinyl polysiloxane impression materials feature superb hydrophilicity and brilliant dimensional accuracy for straight-on stone pours every time. SHARP Medium and Heavy are sturdy tray materials that provide phenomenal compression for SHARP Wash, a light-bodied VPS material that greatly reduces surface tension to achieve accurate impression results. SHARP Clear allows you to cure through the material. For more information, call (800) 243-7446 or visit parkell.com.

Sultan Healthcare

Genie vinyl polysiloxane impression material costs one third less than leading brands. It is easy to extrude and ultra hydrophilic and is available with your choice of 2 set times—rapid (2:10) and standard (4:30). For more information, call (800) 637-8582 or visit sultanhealthcare.com.

Coltène/Whaledent

The AFFINIS family of impression materials provides the perfect systems and materials for taking impressions without voids and distortions. Representing the most advanced vinyl polysiloxane from Coltène/Whaledent, AFFINIS demonstrates unique wetting ability and ideal flow properties to capture all critical details of the preparation in a wet environment. It is the first autoclavable impression material, and it is available in 9 viscosities. For more information, call (800) 221-3046 or visit the Web site coltenewhaledent.com.

Ultradent Products

Chromaclone impression material is a super-hydrophilic and thixotropic vinyl polysiloxane material. It is offered in 3 viscosities with 2 setting times. The light body/wash (light purple), medium body/monophase (maroon), and a heavy body (dark pink) are available in fast set (2.5 minutes) and regular set (4 minutes). A putty (light peach) is also available. Its unique bubblegum flavor makes taking an impression more pleasant for the patient. For more information, call (800) 552-5512.

Pentron Clinical Technologies

Correct Plus hydrophilic impression material is a versatile impression material designed to accommodate all impression techniques. It is now available in 2 set times. A low contact angle of 30° guarantees outstanding detail in the presence of fluids. It is formulated with proprietary nanoparticulate fillers for enhanced performance and it provides exceptional tear strengths. It has a working time of 1:30 and a setting of 3:30, making it the ideal material for full-arch impressions or any situation where a longer set time is desired.

Correct Quick material is a fast-setting line of vinyl polysiloxane impression materials available in several viscosities to accommodate different techniques. It is odorless and tasteless for better patient acceptance. Ease of use, excellent dimensional stability, and high tear strength provide you with an accurate, highly detailed impression.

The Correct VPS system is a full line of vinyl polysiloxane impression materials available in several viscosities to satisfy every technique. It is odorless and tasteless for better patient acceptance. Ease of use, excellent dimensional stability, and high tear strength provide you with an accurate, highly detailed impression.

For more information, call (800) 551-0283 or visit pentron.com.

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