Vinyl polysiloxane impression materials: a status report. Council on Dental Materials, Instruments, and Equipment.

Results of investigations of vinyl polysiloxanes indicate that they produce highly accurate impressions, have excellent elastic recovery, minimal permanent deformation, and adequate tear strength. A number of vinyl polysiloxanes are certified by the American Dental Association. All of these materials provide clinically acceptable results. Advantages of using the vinyl polysiloxanes include the ability of the impression to be poured up after 1 hour or 1 day, or for some products, after 1 week without significant loss of accuracy; the possibility of repouring the impression a second time and producing an accurate cast; the impression materials are available in several viscosities allowing flexibility in choosing an impression technique; and they can be immersed in recommended disinfectants without affecting the accuracy of the impression. The disadvantages of using the vinyl polysiloxanes include a difficulty in lengthening the working time of products without retarders and a high surface tension making it difficult to wet the impression when pouring up a stone cast. Hydrophilic materials appear to facilitate the casting of the impressions with stone. The automixing devices seem to provide convenience without sacrificing the quality of the impression and are currently available for several products. As with all elastomeric impression materials, proper handling is necessary to ensure the best results. The vinyl polysiloxanes seem to be an excellent choice of impression materials for many clinical situations.