13
Elastic impression materials
Component | Amount (%) | Function |
---|---|---|
Sodium/potassium alginate | 15 | Water soluble, reacts with Ca2+ |
Calcium sulfate | 14 | Reacts with potassium alginate to form insoluble gel |
K2SO4, silicates, borates | 10 | Counterbalance gel effect on gypsum |
Sodium phosphate | 2 | Retarder for Ca2+/alginate reaction |
Diatomaceous earth | 70 | Filler |
Colorant, flavoring, disinfectant | Minor/trace |
Grainy material Improper mixing Prolonged mixing Excessive gelation Incorrect W/P ratio Tearing Inadequate bulk Moisture contamination Premature tray removal Prolonged mixing |
Irregular voids Moisture/debris Poor mixing Rough/chalky cast Impression not clean Impression too wet Premature cast removal Delayed cast removal Incorrect mix of gypsum material |
Distortion Delayed pouring Tray movement during set Premature tray removal Incorrect tray removal Excessive gelation Bubbles Overmixing of material Poor mixing technique |
Base paste | Catalyst |
---|---|
Polysulfide polymer, 80–85% Filler (TiO2, ZnSO4, CuCO3, or silica), 16–18% |
Lead dioxide, 60–68% Dibutyl phthalate, 30–35% Sulfur, 3% Minor ingredients, 2% |