types of failure of vinyl polyether silicone (copy)

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ROUGH/ UNEVEN SURFACE ON IMPRESSION

BUBBLES

IRREGULARLY SHAPED VOIDS

ROUGH OR CHALKY STONE

FAULTY ELECTROPLATING

types of failure of vinyl polyether silicone

incomplete polymerization anfd too rapid polymerization

rough/uneven surface on impression is a result of?

: premature removal from the mouth, improper ratio or mixing of accelerator and base, oil or other organic material teeth

incomplete polymerization is caused by?

high humidity or temp

too rapid ppolymerization is caused by?

Too rapid polymerization, PREVENTING FLOW and AIR INCORPORATED during mixing

VINYL POLYETHER SILICONE can have BUBBLES CAUSED BY

-        INADEQUATE CLEANING of impression

-        EXCESS WATER LEFT on surface of the impression

-        PREMATURE REMOVAL of cast

-         IMPROPER MANIPULATION of stone

rouch/chalky stone is caused by

-        dirty surface

-        uneven application of SILVER POWDER to surface of impression

-        AIR BUBBLES TRAPPED when filling impression with silver cyanide solution

-        inadequate current

-        removal from plating bath TOO SOON

-        or reversing anode and cathode

causes of faulty electroplating on polysulfide polymer

should not be plated

causes of faulty electroplating on silicone