Isolation Techniques
Why is it important?
Elastomeric impression materials (polyether, vinyl polysiloxane, condensation silicone, and rubber base) require a dry field to reduce the potential for voids in the final impression.
Types of isolation
Cotton rolls
- Maxillary – place in the buccal vestibule
- Mandibular – place both buccal and lingual to the preparation(s)
Saliva evacuator – as needed
Retraction Techniques
Single-cord technique (see Figure 1)
- Indicated for healthy gingival tissues (minimal hemorrhaging).
- Pack delicate facial aspects of anterior teeth with single cord when possible.
- Cord should remain in place for 10 minutes.

Figure 1. Single-cord technique.
- Double-cord technique (see Figure 2) (ref. 8)
Indicated when bleeding is likely.
First cord packed below the margin (#000 or #00) for hemostasis and to act as a depth gauge.
Second cord packed to help further reflect tissues (#0 or #1).
First cord remains in place while making impression (controls bleeding/deflects tissue).

Figure 2. Double-cord technique.
- Hemostatic agents (e.g. ferric sulfate, aluminum chloride) may be used to help control bleeding and will not inhibit the set of VPS impression materials
(ref. 9)

© 1999 3M. All rights reserved.