## **Core Concept**
Polysulfide impression materials are a type of elastomeric impression material used in dentistry for making impressions of the oral cavity. They are known for their high accuracy and dimensional stability. The working time of an impression material is the time available to mix, place, and remove the impression material from the mouth.

## **Why the Correct Answer is Right**
Polysulfide impression materials typically have a working time of around 4 minutes. This allows sufficient time for the dentist to mix the material, place it in the mouth, and capture the necessary details before it starts to set. The setting reaction involves an oxidation-reduction reaction that leads to the formation of a cross-linked polymer.

## **Why Each Wrong Option is Incorrect**
- **Option A:** 1 minute is too short for the working time of polysulfide impression materials. This duration would not allow sufficient time for mixing, placing, and removing the impression.
- **Option B:** 2 minutes might seem reasonable but is still shorter than the typical working time for polysulfide impression materials.
- **Option D:** 7 minutes might be longer than necessary for the working time, as polysulfide materials usually start to set within a few minutes, and prolonged working times can lead to dimensional inaccuracies.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that polysulfide impression materials have a distinct odor and are known for their excellent tear resistance and accuracy. However, they have a limited working time, typically around **4 minutes**, which requires efficient handling by the dentist.

## **Correct Answer:** C. 4.