Clinicians report that the impression-taking process is the most
stressful restorative procedure. Key factors involved in producing
clinically acceptable impressions include managing soft tissue, appropriately
selecting tray and impression material, and enabling
impression material to flow predictably. Managing soft tissue is
the most critical step in obtaining a perfect impression. Tray selection
also plays a significant role with tray choice depending on the
clinical situation and on the impression material and technique
used. The most commonly used elastomeric impression materials
are polyether (PE) and vinyl polysiloxane (VPS) chemistries.
Appropriate use of either will produce a clinically accurate impression.
The material must have an adequate working time and
flowability, and have sufficient tear strength to prevent tearing at
thin areas at the margin. Using a hydrophilic impression material
and a surface modifier will permit enhanced flow and result in a
more accurate and detailed impression. In addition, the impression
must be dimensionally stable for a reasonable time until it is
cast. Achieving clinically acceptable impressions requires clinical
expertise and appropriate materials, trays, and techniques.