What type of material is most commonly used for preliminary impressions?

The most commonly used material for preliminary impressions is alginate. Alginate is a hydrophilic, irreversible hydrocolloid that is favored for its ease of use, quick setting time, and ability to capture fine details of the oral structures. It is particularly well-suited for preliminary impressions because it is flexible, allowing for easy removal from the mouth without distorting the impression. Alginate is also relatively inexpensive, making it a practical choice for many dental practices.

Silicone, while also used for impressions, is more commonly reserved for final impressions due to its superior dimensional stability and accuracy. Impression plaster is not typically used for preliminary impressions as it can be too rigid and is generally reserved for specific clinical situations. Polyether is another material that is excellent for final impressions but has a longer setting time and can be more expensive, which makes it less ideal for preliminary impressions.

This context highlights why alginate is the preferred choice in this scenario for capturing preliminary impressions effectively.