Impression Materials PDF

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Impression Materials A. Reasons for selecting one material over another: 1. If it becomes necessary to store the impression before a cast will be made – polyethers and PVS are preferable because they have long term dimensional stability 2. If impression will be poured in epoxy or will be electroplat...

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Impression Materials

A. Reasons for selecting one material over another: 1. If it becomes necessary to store the impression before a cast will be made – polyethers and PVS are preferable because they have long term dimensional stability 2. If impression will be poured in epoxy or will be electroplated – reversible hydrocolloid should not be selected because it is compatible only with die stone 3. Advantages and disadvantages of each material

B. Techniques for Mixing Impression Materials 1. One step technique 2. 2-step technique 3. Automix technique – base and catalyst are supplied in a cartridge which is inserted in a gun-like device; mixing occurs as the base and catalyst are extruded from the gun and pass through a mixing tip; advantage is elimination of hand mixing which produces a more consistent mix and lesser voids; automixing is not available for polysulfides 4. Machine mixing technique – a machine mixer is used to mix the impression material which produces a void-free impression and is more convenient...