Dental Materials

HEAT ACTIVATED DENTURE BASE RESIN PROCESSING

POLYMER-MONOMER RATIO

• Powder & liquid are mixed in proper proportions

• Polymer monomer ratio – 3:1 by volume

• Excess monomer – increase polymerization shrinkage

POLYMER –MONOMER INTERACTION

• When monomer &polymer are mixed in proper proportion –workable mass is formed

• Workable mass result in 5 stages:

      I.    SANDY-coarse or grainy

      II.  STRINGY-stringiness or stickiness when material is touched

      III. DOUGHLIKE- ideal for compression molding

      IV. RUBBERY or ELASTIC-mass rebounds when compressed or stretched

      V.  STIFF-resistant to mechanical deformation

DOUGH FORMING TIME

• ADA specification- less than 40 min from start of mix

WORKING TIME

• ADA specification – 5mins ,dough to remain moldable

• Extended by refrigeration