Alginate

Flexible gel

substance deforms when removed from the mouth and springs back to its original form

Sol

means liquid like

Sol to gel formation

temperature change

Hydrophilic

water loving

Colloid

mixture of 2 or more substances in which one substance is suspended or dispersed within another

Gelation Temperature

temperature at which change of sol to gel or jelly occurs

Reversible, irreversible

types of hydrocolloid IM

Reversible Hydrocolloids

hydrocolloids w/ sol – gel – sol

Irreversible

hydrocolloids w/ sol - gel

Agar

ex of reversible hydrocolloid EIM

Alginate

Ex of Irreversible hydrocolloid EIM

Thermoplastic, final impression

classification of agar

Water cooled tray or syringe type

manner of dispensing of agar

Good surface detail, reusable and easily sterilized

advantages of agar

Needs equipment and dimensional instability

disadvantage of agar

Seaweed – basic constituent of agar

Water, agar, borax

composition of agar

Single stroke, sudden jerk, sudden pull

manner of withdrawal of agar

Syneresis

dehydration

Within 15 mins.

dimensional change of agar

Dehydrate

stiff and difficult to remove

Fracture of cast

result of dehydrate

Gelation

solidification process, from sol to gel

Hysteresis

temperature between the gelation temperature and the liquefaction temperature of the gel

Alginate

one of the most widely used IM

Ease of mixing and manipulating, minimum equipment necessary, flexibility of the set impression, accuracy of handled properly, low cost

Thermoset, elastic, prelim anf final IM

classification of alginate

Placed in pouch

manner of dispensing alginate

Type 1 and 2

types of alginate

Type 1 alginate

fast set alginate

Type 2 alginate

slow set alginate

60 – 120 secs

setting time of type 1 alginate

2 – 4.5 mins

setting time of type 2 alginate

NA or K alginate, Ca SO4, Na PO4 , Silicate powder, K Ti fluoride, Organic Glycol, Quaternary ammonium compounds, flavoring and coloring

composition of alginate

Na or K alginate

main ingredient of alginate

Ca SO4

reactor of alginate

Hemihydrate

increases shelf life of the powder and increases dimensional stability of the gel

Trisodium Phosphate

what is NaPO4

Silicate Powder

disperses the alginate powder particles in water

K Ti Fluoride

Plaster Hardener

Organic Glycol

makes alginate dust free

Quaternary ammonium compounds

provide self-disinfection

15-18 grams : 40-50 cc

W/P ratio of alginate

45secs – 1 min

mixing time of alginate

Sudden pull or jerk

withdrawal of alginate

Storage temperature, moisture contamination from the air

factors to consider in the shelf life of alginate

Syneresis

water evaporates

Imbibition

placed in water

4-6 mm thick

thick of land in cast

2-3 mm

depth of peripheral roll

15-20 mm

thick of base