Tissue conditioners as functional impression materials.

Permanent deformation, strain in compression, flow, dimensional stability, reproduction of detail and gypsum compatibility of three commercial tissue conditioners (Coe-Comfort, FITT and Hydro-cast) and one polysulphide base Type I impression material (Coe-flex) were measured according to ADA Specification No. 19. Although the tissue conditioners generally exhibited higher deformations and lower gypsum compatibility than specified by ADA Specification No. 19, the materials can, in all probability, be considered adequate for the present. It would appear that the development of international standards for tissue conditioners and functional impression materials is badly needed.