Before revision: Advantages: Most hydrophilic elastomeric impression material Dimensionally stable – minimal shrinkage on set with release of by-product Good accuracy Monophase impression Good tear resistance Disadvantages: Can be too stiff – deep undercuts and space under a bridge pontic should be blocked out with soft (modelling) wax to prevent inadvertently removing bridge with impression Indications: Indirect cast restorations, especially in cases where moisture control cannot be guaranteed Locating and the pick up of implant analogues in preparation for placement of superstructure Functional impression taking in removable prosthodontics Silicones Impression taken with silicon There are two types of silicone resin impression material, addition and condensation (reflecting each of their setting reactions).
After revision: Advantages: Most hydrophilic elastomeric impression material Dimensionally stable – minimal shrinkage on set with release of by-product Good accuracy Monophase impression Good tear resistance Disadvantages: Can be too stiff – deep undercuts and space under a bridge pontic should be blocked out with soft (modelling) wax to prevent inadvertently removing bridge with impression Indications: Indirect cast restorations, especially in cases where moisture control cannot be guaranteed Locating and the pick up of implant analogues in preparation for placement of superstructure Functional impression taking in removable prosthodontics Silicones Impression taken with silicone There are two types of silicone resin impression material, addition and condensation (reflecting each of their setting reactions).