Acrylic Resin Flashcards
what are the ideal properties of a denture
replaces function of natural teeth
goes into patients mouth
is seen by other people
has to give value for money
what are the ideal properties of a denture base
dimensionally accurate and stable
high softening temperature
unaffected by oral fluids
thermal expansion
low density
high thermal conductivity
radiopaque
non toxic, non-irritant
easy and inexpensive to manufacture
easy to repair
what are the mechanical properties of a denture base
high youngs modulus
high proportional limit
high transverse strength
high fatigue strength
high impact strength
high hardness/abrasion resistance
what is free radical addition polymerisation
chemical union of two molecules either the same or different to form a larger molecule without the loss of smaller molecule
involves molecules with C=C bonds
what are the stages of acrylic polymerisation
activation - provide free radicals
initiation - break C=C bonds
propagation - growing polymer chain
termination - of polymerisation
what is the initiator of a heat cured acrylic powder
benzoyl peroxide
what are the properties of acrylic
non-toxic
non-irritant
unaffected by oral fluids
poor mechanical properties
good fatigue strength
high hardness
thermal expansion same as artificial tooth
low thermal conductivity
low density
high softening temperature
fairly accurate
what is the initiator of a self cured acrylic
benzoyl peroxide but it is activated by tertiary amine in liquid
why use a self cured acrylic
lower temperature so less thermal conduction and better dimensional accuracy
what are the disadvantages of self cured acrylic
low molecular weight so poorer mechanical properties
more unreacted monomer = irritant and soften denture base
water absorption means expansion
how much unreacted monomer is present in self cure
3-5%
how much unreacted monomer is present in heat cure
0.2-0.5%
what attempts are made to strengthen acrylic resin dentures
high impact resistant materials
incorporate fibres
what is ultra hi
high impact heat cure acrylic resin
what properties does ultra hi have
exceptional flexural strength and fracture toughness allowing it to bend a bit which stops it being brittle
