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Terms in this set (42)
Part that sits on soft tissue and holds the fake teeth.
Ideal properties for denture base
Tasteless, odorless, biocompatible, Looks natural, adheres to plastic, metal and porcelain, easy to make and repair, doesn't cost a lot
Most popular Denture base polymer
High-impact, heat-cured Poly(methyl methacrylate) PMMA
Most popular Soft denture liner
Heat cured Silicone
Most popular tissue conditioner
plasticized acrylic. Only lasts a few weeks and can harden the liner.
PMMA powder components
Pre-polymerized PMMA or copolymer beads, initiator, Pigments and dyes, opacifier, external and internal plasticizer, Inorganic filler
PMMA liquid components
Monomer, inhibitor, cross-linker, plasticizer
Pre-polymerized PMMA or copolymer beads use in PMMA
to decrease polymerization shrinkage and make plastic dough
Initiator in PMMA
Benzoyl peroxide dissociation with heat forming free radicals
Pigments and Dyes in PMMA
metal oxide or sulfides, Fe2O3, HgS, dyed Nylon fiber
Opacifier in PMMA
titanium oxide, zinc oxide
External Plasticizer in PMMA
Dibutyl pthalate. Low-molecular weight esters to make plasticized polymer softer and less brittle than a pure polymer.
Internal Plasticizer in PMMA
Big R groups cause increase distance and decrease interaction between polymer chains. Doesn't leach out.
Inorganic Fillers in PMMA
To increase strength and stiffness. Particles includes glass and zirconium silicate. Fibers include glass, alumina, carbon, and silica carbide.
Monomer in PMMA
Methyl methacrylate. Other monomers may be butyl or octyl methacrylate
Inhibitor in PMMA
Hydroquinone. Prevents premature polymerization and prolongs shelf life.
Cross-linkers in PMMA
ethylene glycol dimethacrylate (EGDMA). They make the polymer stronger, more crack resistant, and decreases water sorption and solubility.
How to Polymerize PMMA
Mix the powder and liquid at a 3:1 ratio. Apply a heat of 71-79*C and pressure. Double bonds break and polymerization occurs. No byproduct because it is free-radical addition reaction.
3 steps of PMMA polymerization
initiation, propagation, and termination
Fabricating denture base
Invest wax up, boil out, mix PMMA, pack, process: heat cure (keep below 100*C to stop PMMA from vaporizing), deflask, finish.
Properties of Acrylic Resin: Strength
Properties of Acrylic Resin: Elastic modulus
Properties of Acrylic Resin: Impact Strength
Brittle on Impact
Properties of Acrylic Resin: Fatigue Strength
fairly resistant to fatigue
Properties of Acrylic Resin: Hardness
Properties of Acrylic Resin: Thermal
Poor thermal and electrical conductivity. Heat distorts. High thermal expansion making porcelain teeth hard to bond to.
Shrinkage of PMMA
PMMA shrinks 21%. In 3:1 ratio it's 6-7%. Practically it's 0.2%-0.5% because of restraining of mold.
Properties of Acrylic Resin: Dimensional stability
Pretty good. Heat-activated=0.4% Chemically= 0.1% and light and microwave cured even better.
Properties of Acrylic Resin: Water Sorption
PMMA is relativily high. Can distort or crack if wetted and dryed a lot.
Precedes cracking. Under tension polymeric chains are drawn out into microscopic fibrils.
Properties of Acrylic Resin: resistance to acid and bases
good to excellent
Properties of Acrylic Resin: resistance to organic solvents
Soluble in organic solvents. EGDMA improves resistance. Alcohol can cause crazing
Adhesion of teeth to PMMA
to acrylic teeth is good. Adhesion to porcelain and metals is generally poor and needs mechanical retention or surface treatment.
Color stability in PMMA
Better in heat cured than chemically cured.
4 PMMA colors
Dark pink, Light pink, Original, or light reddish pink
Biocompatibility of acrylics
Usually inert. Hypersensitivity usually to unreacted monomer. PMMA>Polyvinyl. Chemically>Heat>light cured.
MMA copolymerized with butadiene-styrene. Has greater impact strength. Processed the same as heat-cured PMMA
Accelerator in Chemically activated PMMA
Tertiary amine, sulfinic acids and salts.
Problems with chemically cured PMMA
Not as strong. Less color stable because of accelerator. Can turn yellowish. A little more soluble.
Different Base materials
High-volume packable, Fast-processing pourable, Fast-processing packable, Poly vinyl, Resin-based composite
Use of Fast-processing pourable
interim denture, doesn't need to be polished.
Pros and cons of Resin based composite
Requires no flasking, processed by triad machine. Not as strong though
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