Final answer:
All gypsum products share the same essential chemical setting reaction, converting calcium sulfate hemihydrate into dihydrate, though their physical properties can vary.
Step-by-step explanation:
The statement being asked about in the question is related to the setting reaction of gypsum products. There are indeed different types of gypsum products used in dentistry, such as stone (Type III), improved stone (Type IV), and plaster (Type II). While they all are composed of calcium sulfate dihydrate as their main component, they have variations in the particle size, shape, and porosity which affect their mechanical properties.
The setting reaction for all gypsum products is essentially a hydration process where the dry powder, calcium sulfate hemihydrate (CaSO4·0.5H2O), reacts with water to form the dihydrate (CaSO4·2H2O), which is the set material. The reaction can be represented as:
CaSO4·0.5H2O + 1.5H2O → CaSO4·2H2O
Differences in the physical characteristics of the powder influence the amount of water required, which in turn dictates the strength and hardness of the final product.
To answer the question, it is true that all gypsum products essentially have the same chemical reaction for setting, although their physical properties and the precise conditions under which they are processed can vary.