VPS Impression Material: Comprehensive Clinical Review and Selection Guide

VPS impression material, also known as addition silicone or vinylpolysiloxane, is the dominant elastomeric material for final impressions in fixed prosthodontics. Its combination of minimal polymerization shrinkage, predictable dimensional stability across a range of storage conditions, and availability in multiple viscosities for the wash-and-tray technique has made it the clinical standard against which newer digital alternatives are compared. Understanding the chemistry and clinical behavior of VPS helps clinicians select the right product for each case and avoid the technique errors that undermine even the best formulations. For a complete overview of all impression material classes, see our complete guide to dental impression materials.

Material Science: How VPS Impression Material Works

VPS is formed through an addition polymerization reaction between vinyl-terminated polydimethylsiloxane and hydrogen silane, catalyzed by a platinum complex. Because the reaction proceeds by addition rather than condensation, no byproduct is released during polymerization. This is the mechanistic basis for the dimensional stability advantage of VPS over condensation silicone: condensation silicone releases ethanol as a byproduct during setting, producing measurable volumetric shrinkage that addition silicone does not.

Based on articles retrieved from PubMed, a 2017 literature review by Naumovski and Kapushevska (Pril Makedon Akad Nauk Umet, PMID 28991761, DOI: 10.1515/prilozi-2017-0031) examined multiple factors affecting the dimensional stability of silicone impression materials across studies published from 2002 to 2016. The review confirmed the superiority of addition silicone in all dimensional stability parameters compared to condensation silicone, with the primary contributing factor being the absence of polymerization byproduct. VPS materials showed stable dimensional behavior when poured within the manufacturer-specified time window, typically 30 minutes to several hours depending on the formulation.

VPS is available across a viscosity spectrum from extra-light body (1 to 5 Pa.s) used for the wash layer, to light body for syringe application into the preparation, to heavy body and putty for tray loading. All viscosities in a given product line share the same base chemistry and set time, which allows them to be used in simultaneous techniques where both materials are delivered and set in a single seating. Hydrophilicity varies by formulation: most modern VPS products incorporate surfactants to improve wetting in moist environments, though polyether retains a marginal advantage in highly moist conditions.

Clinical Indications for VPS

VPS is the primary material for final impressions in all fixed prosthodontic workflows involving crown and bridge preparation on natural teeth. Its dimensional stability on storage makes it suitable for workflows where the impression must be sent to an external laboratory, which may require 24 to 72 hours before pouring. Goncalves et al. (2011, PMID 22645802) confirmed that VPS impressions stored at 21 +/- 2 degrees C showed consistent dimensional behavior across studies, making temperature-controlled shipping viable for most clinical scenarios.

VPS is also appropriate for implant-level impressions in single-unit cases and for short-span fixed bridges. In full-arch implant impressions, polyether may provide a marginal advantage in tissue detail reproduction due to its greater hydrophilicity, but VPS with modern hydrophilic formulations performs clinically acceptably in most full-arch scenarios. The choice between the two depends on the specific product properties, laboratory preference, and whether the impression trays in the practice are custom-fabricated or stock.

Contraindications are primarily technique-related rather than material-specific. Sulfur-containing compounds, including natural latex gloves, some retraction cords, and zinc oxide eugenol materials, inhibit the platinum catalyst and prevent or delay VPS polymerization. All of these sources must be eliminated from contact with VPS materials before impression taking. This is a preventable error but also one of the most common sources of set failure in VPS use.

Step-by-Step VPS Impression Protocol

1. Tissue management. Achieve hemostasis and subgingival exposure of the preparation margin using retraction cord, electrosurgery, or a combination. The margin must be fully visible and the sulcus dry at the moment of impression.
2. Tray selection and preparation. Select a custom or stock tray with appropriate arch coverage. Apply tray adhesive to the tray internal surface and allow it to dry completely for at least 10 minutes. Omitting tray adhesive is a frequent source of impression failure from material separation on removal.
3. Material preparation. Load the syringe with light-body VPS and the tray with heavy-body or putty using the manufacturer-recommended delivery system. In simultaneous techniques, both materials are ready at the same time before beginning tissue drying.
4. Syringe injection. Dry the preparation area with a short air burst. Inject light-body VPS from the depth of the sulcus outward, working around all margins continuously without withdrawing the tip from the material. Avoid air incorporation.
5. Tray seating. Seat the loaded tray with firm, even pressure immediately after syringe application. Hold in place without movement for the full manufacturer-specified set time, typically 3 to 5 minutes at mouth temperature.
6. Removal and inspection. Remove the impression with a single decisive motion to minimize elastic deformation. Inspect under light for completeness of margin reproduction, absence of voids at preparation margins, and sharp reproduction of all gingival anatomy.
7. Disinfection and dispatch. Disinfect by immersion or spray following your protocol before wrapping and sending to the laboratory. Note impression material type, set time, and any retraction materials used on the laboratory prescription.

Clinical Evidence: Accuracy of VPS

Based on articles retrieved from PubMed, an in vitro study by Rues et al. (2024, Clinical Oral Investigations, PMID 39347818, DOI: 10.1007/s00784-024-05962-2) compared VPS (Aquasil, Dentsply Sirona) and polyether (Impregum, 3M) impressions on a standardized model containing two prepared abutments, an implant, and three reference balls. The study tested both materials with manually fabricated custom trays and multiple 3D-printed tray types. Both materials achieved clinically acceptable global accuracy, with all mean absolute distance deviations below 100 micrometers regardless of tray type. For single abutment accuracy, both materials performed excellently. The study found that impression material type, tray material, and abutment type all significantly affected global accuracy (p < 0.05), confirming that none of these variables can be ignored in clinical practice.

The Naumovski and Kapushevska (2017) review identified impression material thickness as an important variable in VPS accuracy studies: thicker material layers were associated with greater dimensional change, supporting the use of custom trays with a controlled spacer thickness over stock trays without spacer control. The review also highlighted hydrophilicity as a factor in surface detail reproduction, noting that modern surfactant-containing VPS formulations had narrowed but not eliminated the polyether advantage in wet conditions.

Advantages and Limitations of VPS

The primary advantages are high dimensional stability over extended storage times, a broad viscosity range enabling multiple technique options, platinum catalyst reaction that requires no special handling precautions beyond latex glove avoidance, and compatibility with all gypsum pouring materials. VPS can be repoured multiple times without significant dimensional change, which is advantageous when a backup cast is required.

The primary limitations are the susceptibility to sulfur inhibition from latex gloves and zinc oxide materials, which requires protocol discipline to prevent set failure, the hydrophilicity disadvantage relative to polyether in highly moist conditions, and the cost premium over alginate for all-arch records where alginate accuracy is sufficient.

Procurement Considerations

VPS impression material is available from all major dental distributors. The principal commercial products in the US market include 3M Imprint 4 VPS, Dentsply Aquasil Ultra, Kerr Take 1 Advanced, Heraeus Panasil, and Kettenbach Panasil. Pricing for a standard 50 mL cartridge of light-body VPS typically ranges from $35 to $65 depending on brand, distributor, and volume tier. Heavy-body packs run $45 to $80 per standard unit. Practices that compare vendor pricing before placing monthly impression supply orders consistently find 15 to 25 percent variance across distributors on the same product SKUs.

Alara's platform compares VPS impression material pricing across 15+ verified vendors in real time. Practices ordering on a monthly cycle can capture meaningful savings on this recurring category without manual price checks.

References

1. Naumovski B, Kapushevska B. Dimensional Stability and Accuracy of Silicone-Based Impression Materials Using Different Impression Techniques - A Literature Review. Pril (Makedon Akad Nauk Umet Odd Med Nauki). 2017;38(2):131-138. PMID: 28991761. DOI: 10.1515/prilozi-2017-0031

2. Rues S, Depre D, Stober T, et al. Accuracy of polyether and vinylpolysiloxane impressions when using different types of 3D-printed impression trays - an in vitro study. Clin Oral Investig. 2024;28(10):560. PMID: 39347818. DOI: 10.1007/s00784-024-05962-2

3. Goncalves FS, Popoff DAV, Castro CDL, et al. Dimensional stability of elastomeric impression materials: a critical review of the literature. Eur J Prosthodont Restor Dent. 2011;19(4):163-166. PMID: 22645802