alginate

composition of alginate

PCZSPSD

potassium alginate (20%)

calcium sulfate (16%)

zinc oxide (7%)

soluble alginate (main ingredient)

potassium titanium fluoride (6%)

sodium phosphate (1%)

diatomaceous earth (50%)

act as a filler.. if added a proper amount

diatomaceous earth

increases the strength and stiffness of the alginate

diatomaceous earth

Produce a smooth texture

diatomaceous earth

Insure a firm gel surface that is not tacky

diatomaceous earth

procedures of alginate

DIC

dimensional changes - syneresis, imbibition

impression taking

constructiton of master cast using rubber base former

materials: dimensional change

BCMPIE

• Boley gauge 

• Carving knife 

• Metal spatula 

• Plaster bowl 

• Inlay ring 

• Enamel tray

materials: impression taking

ATPMPMP

• Alginate

• Tap water

• Perforated tray 

• Measuring cup or spoon 

• Plaster bowl 

• Metal spatula 

• Plastic sheet

types of dimensional changes

SI

syneresis

imbibition

syneresis

The gel may lose water by evaporation from its surface, or by the exuding of fluid.

imbibition

If a gel is lacking in water content, absorption of water will occur.

impression trays

They are used to carry the impression material to the mouth in its plastic state til it sets

types of alginate

type 1

type 2

type 1

fast setting - 30 secs

type 2

normal setting - 45 secs to 1 minute

measuring alginate

do not tap the scoop more than once or tiwce

• compacts the poowder

• thicker mix

spatulation - mixing

RI

reversible - 1 to 2 mins

irreversible - 2 to 4.5 mins

creamy

proper consistency of mixed alginate impression?

criteria for accessing the impression

LNAFAS

• Lack of void 

• No distortion, clear and distinct impression 

• Adequately extended

• Free of debris and extraneous material 

• Adequate details and all structure must be recorded

• Stable material which is sufficiently attached to the tray

Construction of master cast

DAPMERWTS

• Dental stone 

• Alginate impression 

• Plaster bowl 

• Metal spatula 

• Enamel tray 

• Rubber base former

• Working sheet 

• Trash bag 

• Sand paper

Errors during impression taking

MCMSITT

• Mix too thick 

• Continuous pressure 

• Movement during setting 

• Separation of alginate from tray 

• Inadequate working time limiting flow 

• Teasing the impression while removal 

• Too much air blown to dry the impression moist towel or cotton over impression for storage

Manipulative factors affect the gel weakened strength

If too much or too little water is used in mixing, the final gel will be insufficient spatulation it produces GAINY MIX 

gainy mix

If too much or too little water is used in mixing, the final gel will be insufficient spatulation it produces