In the world of dental impressions, accuracy, dimensional stability, and ease of use are key. One of the most commonly used materials for precise impressions in modern dentistry is VPS – Vinyl Polysiloxane. Known for its superior performance, VPS materials are used for crown and bridge impressions, denture procedures, and various other indirect restorative treatments.
In this post, we'll break down what VPS is, and then go into detail about the different viscosities (heavy body vs light body) and setting times (regular set vs fast set) – helping you select the right material for your clinical needs.
What is VPS (Vinyl Polysiloxane)?
VPS is an addition silicone elastomer, commonly used in dentistry for its:
- High dimensional stability
- Excellent tear resistance
- Long shelf life
- High accuracy and fine detail reproduction
- Ease of disinfection without distortion
These qualities make VPS ideal for final impressions in fixed prosthodontics, implants, and sometimes even removable prosthodontics.
Viscosities of VPS: Light Body vs Heavy Body
VPS comes in various viscosities, most commonly:
Light Body (Low Viscosity)
- Purpose: Used for capturing fine detail around prepared margins.
- Application: Syringed directly around the tooth or implant site.
- Flowability: Excellent; flows easily into sulcus and around fine structures.
- Use with: Typically used in a two-step or dual-viscosity technique alongside a heavier body material.
Pros:
- Superior marginal detail
- Adapts well to soft tissues and complex anatomy
Cons:
- Too runny to use alone for full arch or structural support
Heavy Body (High Viscosity)
- Purpose: Provides support and prevents distortion of the light body material.
- Application: Loaded into a tray and seated over the light body impression.
- Flowability: Thicker and more resistant to flow.
Pros:
- Helps push light body into critical areas
- Offers good tray support and overall structural strength
- Ideal for dual-viscosity or two-step impressions
Cons:
- Not ideal for capturing fine detail on its own
Other viscosities:
- Medium Body: A balance between light and heavy; used in monophase techniques.
- Putty: Very high viscosity, often used in two-step putty-wash impressions.
Setting Time: Regular Set vs Fast Set
Regular Set VPS
- Working Time: ~2:30 to 3:00 minutes (varies slightly by brand)
-
Setting Time: ~5 to 6 minutes total in the mouth
Best For:
- Complex cases requiring more time
- Full arch impressions
- Less stressful environments
Advantages:
- More time to syringe around margins
- Useful in multi-unit cases or with slower workflows
Fast Set VPS
- Working Time: ~1:00 to 1:30 minutes
- Setting Time: ~2:30 to 3:30 minutes in the mouth
- Best For:
Single unit crown or bridge
Patients with strong gag reflex
When time is limited or patient cooperation is challenging
Advantages:
- Shorter chair time
- Improves patient comfort
- Reduced chance of movement during setting
Clinical Decision Guide
| Case Type | Suggested Viscosity | Suggested Set Time |
|---|---|---|
| Single Crown | Light Body + Heavy Body | Fast Set |
| Multiple Crowns | Light Body + Heavy Body | Regular Set |
| Implant Impression | Light Body + Heavy or Medium Body | Regular Set |
| Full Arch Denture | Medium Body or Putty | Regular Set |
| Gag Reflex Patient | Light + Heavy Body | Fast Set |
Tips for Successful VPS Impressions
- Always bleed automix cartridges before use to ensure a uniform mix.
- Keep the sulcus dry and retracted for the best margin capture.
- Use a dual-arch tray with caution – only for cases with stable occlusion.
- Avoid latex gloves when handling VPS, as they may inhibit polymerization.
- Disinfect impressions properly but avoid long immersion in solutions.