HESI General Chairside Assisting Practice Exam

Which dental material requires the greatest quantity of water for mixing?

1. Gypsum

2. Model plaster

3. Type I ZOE

4. Composite resin

The correct answer is: Model plaster

The correct answer is model plaster, as this dental material specifically requires a significant amount of water for proper mixing and consistency. Model plaster is used for creating dental casts and requires a higher water-to-powder ratio compared to other materials to achieve a workable mix. The substantial water content aids in making the plaster smoother and more manageable when pouring into dental impressions. In contrast, gypsum materials can vary in their water requirements, with different types of gypsum having specific mixing ratios. Type I ZOE, which is a type of dental cement, does not require the same high water content, as it is designed for other purposes such as temporization and filling. Composite resins also have minimal water requirements and typically utilize a bonding agent instead, which does not necessitate additional water during preparation.