This high-yield revision note on Impression Materials: Alginate, PVS, Polyether - Properties & Uses covers everything examiners typically test under Dental Materials — structured as quick-reference tables, clinical correlations, mnemonics and previous-year-style high-yield points. It's built for last-mile revision before NEET MDS, INI-CET MDS and INBDE, so you can scan it in minutes instead of re-reading a whole textbook chapter.
| Material | Type | Setting | Key Property |
|---|---|---|---|
| Alginate | Irreversible hydrocolloid | Chemical (sol→gel), sodium alginate + calcium sulfate reactor → calcium alginate | Poor dimensional stability - imbibition (water storage) or syneresis (dry storage); pour within 15 min ideal |
| Agar | Reversible hydrocolloid | Physical (temperature dependent, sol at 70°C → gel at mouth temp) | Excellent accuracy, needs water-cooled tray, technique sensitive |
| Polyvinyl siloxane (PVS/Addition silicone) | Elastomer | Addition (polymerization) reaction, catalyst = Pt salt | Best dimensional stability & accuracy, hydrogen gas release (wait 30 min before pouring or use gas-free type), highest cost |
| Polyether | Elastomer | Cationic ring-opening polymerization | Very rigid/stiff, high accuracy, hydrophilic (good for moist fields), can absorb water & distort if stored wet, difficult removal from undercuts |
| Condensation silicone | Elastomer | Condensation reaction, byproduct ethyl alcohol evaporates | Poor dimensional stability (shrinkage from byproduct evaporation) - pour immediately |
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