Which of the following is NOT among the most commonly used elastomeric impression materials?

• A. Alginate
• B. Polysulfide
• C. Polyether
• D. Silicone

Answer: (A)

Elastomeric impression materials are rubbery polymers used for final impressions because they resist distortion and reproduce fine detail. Alginate, however, is an irreversible hydrocolloid used mainly for preliminary impressions and is not considered an elastomer. The materials that are commonly used as elastomers for final impressions include polysulfide, polyether, and silicone, which all offer better dimensional stability and tear strength than alginate. Therefore, alginate is the item that does not belong with the elastomeric group, making it the correct choice.