Which statement describes alginate?

• A. Alginate is an irreversible hydrocolloid that is hydrophilic and inexpensive.
• B. Alginate is a reversible hydrocolloid that is hydrophilic and inexpensive.
• C. Alginate is a zinc oxide cement.
• D. Alginate is a polyether-based material.

Answer: (A)

Alginate is an irreversible hydrocolloid, meaning it changes from a sol to a gel through a chemical setting reaction and cannot revert to liquid with heat. It’s hydrophilic, so it wets the oral tissues well and captures details even if moisture is present, which helps reduce voids. It’s inexpensive, making it a common choice for routine or preliminary impressions. It’s not a reversible hydrocolloid (that would be agar, which requires heating to liquefy and re-set), not a zinc oxide cement, and not a polyether-based material, all of which belong to different classes with different用途 and properties.