Alginate is irreversible hydrocolloid. Which option lists the correct material for irreversible hydrocolloid?

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Multiple Choice

Alginate is irreversible hydrocolloid. Which option lists the correct material for irreversible hydrocolloid?

Irreversible hydrocolloid is a gel that forms through a chemical change and cannot be melted back into a sol. Alginate fits this description because it gels when calcium ions crosslink the alginate molecules, creating a stable calcium alginate gel that cannot revert to liquid by heating. That’s why alginate is the material classified as irreversible hydrocolloid. Agar, by contrast, is a reversible hydrocolloid: it can be melted and then cooled to reform the gel, which is why it’s not irreversible. Polysulfide and polyether are elastomeric impression materials that set by polymerization, not hydrocolloid gel formation.

Irreversible hydrocolloid is a gel that forms through a chemical change and cannot be melted back into a sol. Alginate fits this description because it gels when calcium ions crosslink the alginate molecules, creating a stable calcium alginate gel that cannot revert to liquid by heating. That’s why alginate is the material classified as irreversible hydrocolloid.

Agar, by contrast, is a reversible hydrocolloid: it can be melted and then cooled to reform the gel, which is why it’s not irreversible. Polysulfide and polyether are elastomeric impression materials that set by polymerization, not hydrocolloid gel formation.

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