DENTAL Materials Lesson 5 Hydrocolloid

1. INGREDIENTS Water % Agar-agar- Seaweed- 15% Borax- sm amt for strength and inhibit set Potassium sulfate- 2%, compitable with stone Fillers and coloring agents

2. Uses and Advantages Final impression for removable prosthesis Impression for fixed castings To duplicate models ACCURATE Inexpensive Hydrocolloid changes physical state from a solid (gel) to a liquid (sol) and back with temperature changes.REVERSIBLE No CHEMICAL REACTION

3. Forms Tubes of heavy or regular body for tray Carpules of syringe material

4. Supplies Tray material Syringe material and syringe 2x2 to wipe smear layer on tray Water cooled tray and hose Hydrocolloid conditioning unit

5. Conditioning unit 1.Boil- 212F for 10 minutes, can reboil 4 times 2.Store- 150F 5 days 3.Temper- tray material only, 115F for 5 min In mouth in water cooled tray for 5 min

6. Gingival Tissue A retraction cord or ring, often soaked in a hemostatic agent, is packed into the sulcus with a gingival retraction instrument, prior to taking the impression. One or two cords may be used.

7. Syringe Material The syringe material is not tempered. When the 5 minutes is up for tempering the tray material, the syringe material is loaded into a syringe and passed to Dr. just before wiping smear layer, connecting hose and passing the tray.

8. The Tray The tray is removed from the tempering bath after 5 minutes. Wipe the top smear layer with a 2X2 so that the syringe material will adhere to the tray material. This also removes excess water. Hook the water hoses to the tray and insert. Flip water switch on to begin the cooling once the tray is seated.

9. Remove the tray A “snap” technique, just like alginate, is used to remove the tray. Always protect the teeth of the opposing arch with your other hand.

10&11. Pour UP Pour up ASAP with Die Stone (22/100) or wrap in wet towel for a short time. Syneresis (drying out) or Imbibition (swell with fluid) can occur if not handled correctly. Separate when set so that the surface of the gypsum is not chalky and weak.

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