Which statement best describes the dimensional stability of alginate compared with elastomeric impression materials?

Which statement best describes the dimensional stability of alginate compared with elastomeric impression materials?

• A. Alginate remains dimensionally stable after removal.
• B. Elastomeric materials have poor dimensional stability.
• C. Elastomeric materials have superior dimensional stability and can be poured after longer storage if sealed.
• D. Alginate must be poured immediately after removal.

Answer: (C)

Dimensional stability refers to how faithfully an impression preserves its size after setting and removal. Alginate, a hydrocolloid, is prone to water movement with its environment—loss of water (syneresis) or uptake of water (imbibition)—which causes shrinkage or distortion as time passes. Elastomeric impression materials cure into a rigid rubbery network with very small dimensional change, making them much more stable after setting. When elastomerics are stored sealed, moisture exchange is minimized, so they can be poured after a longer delay without losing accuracy. That’s why the best description is that elastomeric materials have superior dimensional stability and can be poured after longer storage if sealed.

Dimensional stability refers to how faithfully an impression preserves its size after setting and removal. Alginate, a hydrocolloid, is prone to water movement with its environment—loss of water (syneresis) or uptake of water (imbibition)—which causes shrinkage or distortion as time passes. Elastomeric impression materials cure into a rigid rubbery network with very small dimensional change, making them much more stable after setting. When elastomerics are stored sealed, moisture exchange is minimized, so they can be poured after a longer delay without losing accuracy. That’s why the best description is that elastomeric materials have superior dimensional stability and can be poured after longer storage if sealed.