Dental Materials M6

DENTAL MATERIALS M6

•

FLASH • Excess resin

•

LAND •

•

TRIAL •

Investing medium

• Alternate opening and closing of the flask to remove the flash from the land

•

Important to remove RESIDUAL MONOMER (excess) HEAT CURED o Longer time o 0.2 – 0.5 % SELF CURED o 3–5% RESIDUAL MONOMER o Causes irritation Rugae are left for more hold

COMPRESSION MOLDING TECHNIQUE • Packing of resin following trial closure INJECTION MOLDING • Resin is injected in the mold space • Eliminates manual factor of opening and closing CURING • Technical term for heating process of resin SELF-CURED • COLD CURED/ CHEMICALLY-ACTIVATED/ ROOMTEMPERATURE RESIN/ AUTOPOLYMERIZING

•

Doesn’t need heating process because of DIMETHYL PARATOLUENE (component of monomer)

HEAT CURED • Activated by heat for complete polymerization METHODS: • RAPID CURING o 74°C water bath for 2 hours leave it for 1 hour at 100°C • SLOW CURING o 74°C for 8 hours or overnight o 74°C for 8 hours let it boil for 1 hour to have complete curing process DIMENSIONAL CHANGES WHILE CURING • THERMAL EXPANSION o Sudden increase of temperature o POLYMERIZATION SHRINKAGE • CONTRACTION • THERMAL CONTRACTION o Sudden drop of temperature • Boiling point of monomer = 100.8°C o It will be porous if it reaches boiling point EXTERNAL POROSITY • Seen clinically outside the denture INTERNAL POROSITY • Found at the thickest bulk of the denture due to too rapid curing process *Bench cool the denture for 30 minutes before placing under running water for 5 – 10 minutes Self Cured is more dimensionally stable • No thermal expansion and thermal contraction because there is no change in temperature • Less color stable Heat Cured is stronger • Undergoes complete polymerization DEFLASKING • Removing of finished denture base from the flask POLISHING

-Rosette Go 012709 