Which component is adjusted by manufacturers to create regular and fast-set alginate impression materials?

The component adjusted by manufacturers to create regular and fast-set alginate impression materials is sodium phosphate. This compound acts as a retarder in the setting process of alginate materials. By modifying the amount of sodium phosphate, manufacturers can control the setting time of the alginate. In regular-set materials, the amount of sodium phosphate is higher, allowing for a longer working time before the material starts to set. Conversely, in fast-set materials, less sodium phosphate is used, resulting in a quicker setting time.

Diatomaceous earth, calcium sulfate dihydrate, and potassium sulfate are all essential components of alginate impression materials but do not specifically control the setting time in the way that sodium phosphate does. Diatomaceous earth primarily serves as a filler that adds bulk and consistency, calcium sulfate dihydrate participates in the setting reaction by providing calcium ions, and potassium sulfate promotes better plaster compatibility but does not directly influence the setting speed. Therefore, sodium phosphate plays a critical role by allowing the adjustment of the working and setting times according to clinical needs.