Denture Base Resin, Processing, Lab Remount Flashcards
resin
a broad term used to describe natural or synthetic substances that form plastic materials after polymerization
acrylic
designating a colorless, pungent acid
denture base polymers (6)
vulcanite polystyrene vinyls nylons PMMA urethane dumethacrylate (light activated)
PMMA resin (8)
excellent esthetic properties adequate strength low water sorption low solubility non-toxic, low allergenicity easily repaired reproduces detail accurately simple molding and processing technique
other resins may outscore PMM in some one property, but
no existing resin scores so high in the aggregate
PMMA resin ingredients (5)
liquid monomer: methyl methacrylate powdered polymer: polymathy methacrylate plasticizer: dibutyl phthalate initiator: benzoyl peroxide pigments
PMMA resin as a two component system
liquid monomer
powdered polymer
PMMA liquid (3)
methyl methacrylate
glycol dimethacrylate- a cross linking agent
hydroquinone- inhibitor for increased shelf life
PMMA powder (4)
PMMA beads
pigments
plasticizer (dibutyl phlkalate)
benzoyl peroxide- initiator of polymerization
types of cure (3)
heat
chemical light
heat activated denture base (3)
used in fabrication of all denture base
thermal energy required for polymerization- water bath or microwave oven
heat activated denture base components (4)
powder- prepolymerized spheres of PMMA and small amount of benzoyl peroxide (initiator)
liquid- predominantly non polymerized methyl methacrylate with small amount of hydroquinone (inhibitor)
cross linking agent is added to liquid
Compression Molding
A technique to process denture
resins
injection molding technique
porosity (3)
internal porosity- but none on surface- likely cause is temperature rise avocet 100C inside flask
monomer builds at 100.8C
spherical bubbles inside resin
internal porosity: monomer boils (2)
heat at surface of resin is conducted away into investing medium, hence no porosity yon surface resin
this vaporization of the monomer affects the thick areas of denture base
other porosity (4)
irregular shape, located throughout the base:
- inadequate pressure
- not enough resin in mold
- improperly mixed resin
resin denture teeth (2)
are basically the same composition as the denture base resin, except for pigmentation to produce tooth shades
are highly cross linked resin, teeth and base chemically bond to each other
chemically activated denture base resin (3)
- induce the denture base polymerization
- does not require thermal energy, made in room temp
- chemically activated resins also referred-cold curing, self curing or qutopolymerizing resins
chemically activated denture base resin composition (3)
liquid (monomer)- addition of tertiary amine like dimethyl-para-toludine
- tertiary amines causes decomposition of benzoyl peroxide
- mold preparation and resin packing is same as heat activated resin
auto polymerized resins
an amine in the liquid reacts with the benzoyl peroxide in the powder to promote polymerization at room temperature
heat-activated vs autopolymerized (3)
- fundamental difference is the method of activation of the inhibitor benzoyl peroxide
- a greater degree of polymerization with heat activated
- better color stability with heat activated
color stability of auto polymerized
the tertiary amine activator (dimethyl-p-toluidine) in the liquid oxidizes and turns orange after a few months
light activated denture base resins (8)
- composite matrix of urethane dimethacrylate, microfine silica, and high molecular weight acrylic resin monomer
- activator: visible light
- initiator: camphorquinone
- supplied in sheet and rope form packed in light proof pouches
- light activated resin cannot be flashed in conventional manner
- opaque investing media provides the passage of light
- teeth is arranged and the denture base sculpted using light activated resin
- denture base is placed into a light chamber and polymerized
