Which impression material exhibits the least dimensional change over time?

Addition silicone, also known as vinyl polysiloxane, is recognized for its outstanding dimensional stability compared to other impression materials. This means that it maintains its shape and size effectively over time, which is crucial for accurate impressions, particularly in prosthodontics and orthodontics.

The superior dimensional stability of addition silicone is largely due to its chemical formulation, which allows it to resist shrinkage and deformation after the initial setting phase. Additionally, it has a low viscosity and good flow properties, which enable it to capture fine details while also retaining its shape without significant dimensional changes.

Reversible hydrocolloid, although it has some advantages in detail reproduction, can undergo dimensional changes due to moisture loss or thermal changes. Irreversible hydrocolloid is more prone to distortion and has less stability over time due to its water content and susceptibility to syneresis (loss of water) or imbibition (absorption of water). Polysulfide, while a commonly used material for impressions, also exhibits dimensional changes over time primarily due to its tendency to undergo elastic recovery and has lower stability compared to addition silicone.

These factors collectively outline why addition silicone emerges as the best choice for impressions requiring high accuracy over extended periods, solidifying its reputation within dental practice