Which impression material has the longest dimensional stability?

The impression material renowned for having the longest dimensional stability is polyvinyl siloxane (PVS). This material is favored in dentistry because of its excellent accuracy, detail reproduction, and stability over time. PVS materials possess a unique formulation that allows them to resist changes in dimension due to environmental factors such as humidity and temperature, which are common concerns with other impression materials.

Unlike agar, which is hydrophilic and can absorb moisture, leading to potential distortion, or alginate, which is not dimensionally stable over time and can shrink or expand depending on the conditions, PVS maintains its shape reliably. Polyether, while also known for its good dimensional stability, does not outperform PVS in terms of longevity and resistance to distortion.

Thus, PVS stands out as the material that provides the greatest stability, making it a preferred choice for detailed and precise impressions in various dental applications.