Orthodontics 5th Year SC Practice Exam

Alginate impressions change size after setting because the gel experiences water movement with the surrounding environment. Water can leave the gel (syneresis) causing shrinkage or be absorbed (imbibition) causing expansion. The most noticeable dimensional change happens within the first several minutes after removal, and the shrinkage tends to become evident around the ten-minute mark. That makes ten minutes the best choice for when shrinkage is expected to occur.

The other options don’t fit as well because shrinkage isn’t typically detectable at just one minute, and while some change can occur by five minutes, it’s not as consistent a window as ten minutes. Waiting as long as forty minutes would likely lead to more distortion due to ongoing water movement and evaporation.