DENTAL Materials
Lesson 5 Hydrocolloid
1. INGREDIENTS
• Water- 80-85%
• 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 • ACCURATE
removable prosthesis • Inexpensive
• Impression for fixed
castings
• To duplicate models 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.
THE END