**Core Concept**
Dental plaster and dental stone are types of dental materials used for casting and impression making in dentistry. They are both based on calcium sulfate hemihydrate (CaSO4·½H2O) but differ in their physical properties and applications.

**Why the Correct Answer is Right**
The main difference between dental plaster and dental stone lies in their particle porosity. Dental plaster has larger, more porous particles, which results in a more porous final product. In contrast, dental stone has smaller, more dense particles, leading to a more compact and durable product. This difference in particle porosity affects the setting time, strength, and thermal expansion of the final product. Dental stone is used for making accurate casts and dies, while dental plaster is used for making impressions and temporary restorations.

**Why Each Wrong Option is Incorrect**
**Option A:** Solubility is not the main difference between dental plaster and dental stone. While dental stone is generally more resistant to water and solvents, this is not the primary distinction between the two materials.

**Option B:** Shelf life is not directly related to the difference between dental plaster and dental stone. Both materials have a similar shelf life, and their storage conditions are not significantly different.

**Option C:** Chemical formula is the same for both dental plaster and dental stone, which is calcium sulfate hemihydrate (CaSO4·½H2O). The difference lies in their physical properties, not their chemical composition.

**Clinical Pearl / High-Yield Fact**
Remember that dental stone is more suitable for making accurate casts and dies due to its higher density and lower porosity. It is also more resistant to thermal expansion, making it ideal for applications where dimensional stability is critical.

**Correct Answer:**
✓ Correct Answer: D. Particle porosity