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) Copyright © 1999 3M. All rights reserved.