Cold Mould Seal-Separating Medium

Cold Mould Seal-Separating Medium

Question 1. What is the mechanism of action of cold mould seal?
Answer:

When cold mold seal is applied to dry plaster surface sodium alginate reacts with calcium sulphate to form insoluble skin of calcium alginate on the plaster surface which in turn blocks the porosities on the surface of plaster. Thus, any other material that comes in contact with plaster will not adhere to it.

Question 2. Compare and contrast dental plaster, dental stone and die stone.
Answer:

Question 3. Write a short note on WET strength.
Answer:

Wet strength is the strength property of gypsum.

• It is also known as green strength.
• Wet strength is the strength obtained when the water in excess of that required for hydration of hemihydrates is left in the specimen.
• Wet strength is lower as compared to dry strength.
• The wet strength (1 hour compressive strength) for model plaster is 12.5 MPa, for dental stone is 31 MPa and for die stone is 45 MPa.