Flashcards in Denture materials Deck (48):
Whats an intalgio?
negative of the cast. Made with impressions
common things were looking for in impression material
biocompatible, excellent detail, odorless, tasteless, non-irritating, immune to oral fluids, easy to mix, short working time, disinfectible, good shelf life, cost effective.
3 classifications of impression materials are
non-elastic, synthetic elastomers, hydrocolloids.
name some non- elastic materials
impression plaster, impression compound, impression waxes
name some synthetic elastomers
polysulphides, polyether, silicones
name the 2 types of hydrocolloids
low molecular weight that increases to become more viscous. Has a base and catalyst and are long crosslinked chains
is thermosetting plastic reversible?
no its irreversible
define viscosity and how its tested.
resistance to stress, tested by shark fin test
what are the ADA requirements for non-aqueous elastomers?
mixing time under 1 min.
working time over 2 min.
does low or high viscosity material catch more details?
ADA non-aqueous elastomeric materials types 1 &2 detail reproduction must be 20 micrometers while type 3 is what?
type 1 &2 elastic limit is greater than 2.5% but type 3 is what?
greater than 6.6 %
maximum change in demension in 24 hr period for types 1 & 3 is less than .5 % while type 2 is
less than -1 %
with polysulfides, which group causes chain lengthening and crosslinking by oxidation?
what causes the mixture to be brown?
pbO2, lead oxide
what makes the polysulfide brown paste we used?
lead oxide+polysulfide polymer--> larger polysuflide polymer+ water
what are some posittives of polysulfides?
elastomeric, flexible, high tear resistance, strong, long working time
what are some negatives of polysulfides?
messy, odor, stains clothes, slow setting time
what is the base and catylist in polysulfide impression materials?
catalyst- lead oxide
what is the base in polyether materials?
base-polyether polymer, filler/silica, plasticizer/phthalate or glycoesther.
what is the catalyst in polyether materials?
alkyl aromatic sulfonate, filler and plasticizers, octyl phthalate, 5 % methyl cellulose - thinning agent
good tear strength, no water released in reaction, shorter setting time
negatives for polyethers
absorb humidity( distortion), avoid sun,
Si, semi-metal used for electronics
SiO2 or silicone dioxide, examples are quartz & glass.
polymoers that include Si, C, H, O
type 1 condensation silicone materials
dimethyl siloxane+ tetra-ethyl orthosillcate= silicone rubber+ ethyl alcohol
releasing of ethyl alcohol does what?
causes shrinkage, this can be avoided by using 2 step putty wash method
type 2, PVS, addition silicone materials.
some siloxane+chloroplatinic acid ( a hydrid group)--> silicone rubber ( paladium is added to absorb hydrogens)
whats special about type 2?
fastest working and setting times
what material is used for mucostatic impressions?
Historical teeth used in dentures were made of what?
human teeth, bovine, hippo teeth, ivory
historical bases used in dentures were made of what?
porcelain denture teeth
mechanically attached ( anterior teeth have pins, posterior have diatoric spaces)
traits of porcelain teeth
esthetically better than acrylic, more resistant to wear, harder to grind, make clicking noise.
Acrylic resin teeth
chemically bond to base,fluorescent, various shades, multiple layers, anatomically correct.
before 1853 what was used for denture bases?
wood, bone, ivory, ceramics
after 1853 what was used for denture bases?
vulcanized rubber, celluloid which is a nitrocellulose material
characteristics of vulcanized rubber
formed the base and was unnatural looking, dark reddish brown color
characteristics of celluloid
formed the gingival area. it was flexible but would absorb stains and develop odors and was flammable.
what is PMMA?
polymethylmethacrylate resin. This is a acrylate polymer. There is a liquid and powder component that polymerize when mixed.
is the pre polymerized polymer
non- polymerized monomer
what is the polymer to monomer ratio of acrylic polymerization
3 polymer to 1 monomer
what happens during acrylic polymerization?
carbon carbon bonds are created which decreases space and causses shrinkage
what is relining a denture?
replacing the tissue surface side