Alginate Impression material

Alginate  (Irreversible hydrocolloid) is an elastic, irreversible hydrocolloid material, and one of the most frequently used dental impression materials. The paste-form of Alginate yield better quality than the powder-form.

The advantages of Alginate impression material are:
  1. It is simple to use. Mix the powder (the most popular form) with water according to the manufacturer guidance which is approximately 60
  2. seconds for hand mixing and 15 seconds for mechanical mixing device (Alginator).  If the water supply contains a large amount of minerals that may affect the setting time of the alginate; use distilled or demineralized water.  Newly supply of paste forms with different viscosities are available in syringe and tray types.  These types of Alginate yield better accuracy.

  3. Cost-effective 

  4. Quick setting that can be controlled by the temperature of the water used

  5. Pleasant mild flavor

  6. Alginate impression can use in the presence of saliva or blood

  7. Alginate is non-toxic and non-irritant, ideal for allergy prone patients

  8. Alginate has enough elasticity to use at the mild undercut areas
The disadvantages of Alginate impression material are:
  1. The impression from an alginate is less accurate than the elastomeric impression materials. 

  2. Poor dimensional stability especially in warm temperature

  3. Cannot use alginate in the deep undercut areas 

  4. Each impression can only be used (poured) once 

  5. Must wait 10 minutes before pouring the impression due to elastic recovering quality.  Keep the impression moist with damp gauze in a zip lock plastic bag while waiting to pour.
Common use of Alginate:
  • For preliminary impressions. In new patient, the dentist uses the model poured from alginate impression to study the patient's occlusion and obtain
    other information necessary for treatment planning.

  • For provisional crown-and-bridge impressions, 

  • For impressions in orthodontic models

  • Impression for mouth guards, 

  • Impression for bleaching trays

  • Used as a final impression in indirect restorations when the preparation margins are chamfer 
Chemistry components in the powder:
  • Sodium alginate
  • Calcium sulfate
  • Trisodium phosphate
  • Diatomaceous earth
  • Zinc oxide
  • Potassium titanium fluoride

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