HESI General Chairside Assisting Practice Exam

Which impression material is commonly prepared for creating a crown working model?

1. Alginate

2. Polyether

3. Vinyl polysiloxane

4. Reversible hydrocolloid

The correct answer is: Vinyl polysiloxane

Vinyl polysiloxane is the correct choice for creating a crown working model due to its excellent properties for capturing fine details and providing dimensional stability. This material is well-regarded in dental practice because it can accurately replicate the contours and textures of prepared tooth surfaces. Its low viscosity allows for easy handling and flow into the areas around the prepared tooth, ensuring that all necessary details are captured for the crown's precise fit. The other materials listed may have their own applications in dentistry, but they do not offer the same level of detail and stability that vinyl polysiloxane provides. Alginate, for instance, is often used for study models and preliminary impressions, but it lacks the accuracy required for crown fabrication. Polyether is known for its good detail and moisture tolerance but can be more rigid and less forgiving compared to vinyl polysiloxane. Reversible hydrocolloid is more commonly used for impressions where flexibility is needed, but it does not match the fine detail reproduction capacity necessary for a crown working model. Thus, vinyl polysiloxane stands out as the optimal material for this specific dental application.