Test #2-3 Flashcards
What are the requirements of impression material
ease of manipulation resonable cost adequate viscosity properites safety pt acceptance compatability with die adequate shelf life appropriate setting time
what should be the mechanical strength of impression materials
should resist tearing and permanent deformation during removal
what is an important requirement of imp material
dimensionally accurate
when are impressions used during fixed restorations
crowns, bridges, inlays, onlays, study models
what are impressions used for in removable appliances
pediatric, ortho appliances, dentures, partials, study models
what are impressions used for in esthetic appliances
bleaching trays, temporary partials
what is rigid
unable to remove from undercuts
what is flexible
capable of removal from undercuts
what is a hydrocolloid
a colloidal suspension in which water is the liquid*
what is a colloid
substance dispersed evenly throughout another substance * liquid/solid/gas
agar
organic hydrophilic colloid extracted from seaweed
what are reversible hydrocolloid steps
- advanced prep of material
- prep immediately before impression
- impression
what are the components of a reversible hydrocolloid
agar, thixotropic materials, structure, thickness
What is an example of a irreversible hydrocolloid*
alginate
what are alginate impressions accurate enough for
study models, working casts, pt education , bleach trays, essex trays, temps
- what can alginate not be used for
-to fabricate indirect restorations
can alginate be softened after setting
no
what is imbibition*
taking on water
what is syneresis*
shrinkage
what does warm water do to alginate*
accelerates reaction
what does cold water do to alginate*
slows reaction
how does alginate set
by chemical reaction
what are inelastic/rigid impression materail
plaster, compound, ZOE
What is ZOE used for*
impressions, bite registration, perio dressings, temp cements, temp restorative materials
When can you use a rigid/inelastic impression compound
for single tooth impressions
What is the viscosity of a flexible elastomeric-rubber base impression material
light body (low viscosity, better flow/detail)
When is regular body elastomeric used
when detail is not critical
when is heavy body elastomeric used
for the bulk of the tray-stability
how is the elastomeric impression material packaged
- 2 tubes: light, medium, heavy body
- cartridge
- disposable pouches
- putty
how many types of rubber bases are there
4
what is a polysulfide rubber base*
catalyst is lead-hazardous
oldest rubber base
sulfur- bad odor
what is a polyether rubber base
shortest working time
can pour repeatedly in 24 hrs
irritates skin
poor tear strength
what are condensation silicone rubber bases
- base dimethyl siloxane
- catalyst- tin octoate
- gives off water/shrinks
- less flexible than addition silicones
what are addition silicone rubber bases
polyvinylsiloxane
most popular and most costly
no shrinkage as it sets
what are some qualities about addition silicones
more accurate and stable
tasteless odorless colorless
doesnt stain clothes
quick and easy to mix
gypsum
calcium sulfate, mined from the earth and processed
what is gypsum used for
models, indirect and direct restorations, mouth guards, bleach trays
what are models
replicas of hard and soft tissue for study
what are casts
working replicas of hard and soft tissues for use in the fabrication of appliances or restorations
what is a die
working replicas of one or more teeth used for fabrication of a restoration
what is an expoly die*
- resin molecule
- made by mixing epoxy material and forcing into the impression
what is electroplating*
metal plating by electrolysis, plated to form metalized working dies
what is electrolysis*
the decomposition of a substance by passage of an electric current through it
What is made from calcium dyhydrate*
all gypsum products, plaster and stone
when calcium hemihydrate powder is mixed with water for impression it reacts with the hemihydrate it then ________________*
reverts back to a dihydrate
What color is plaster
white
What kind of particles does platster have
porous irregularly shaped particles
what color is dental stone
buff or yellow color
what are the particles like in stone
denser more regular shaped particles
What color is die stone
pink, green , blue or yellow
What are factors that determine properties of gypsum products
size, shape, and porosity of the particles
what are the desireable qualities of gypsum products
accuracy, dimensional stability, fine detail, strength and resistance to abraision, ease of adaption
waht kind of reactions do gypsum products have
*exothermic
** what is the written mixing reaction
calcium sulfate hemihydrate (plaster/stone)-calcium sulfate dihydrate (gypsum)+ heat
what does extra water do to the setting time of model and die materials
increases the setting time
**When you increase the temp of the water for model and die materials what happens? decrease the temp?
- faster setting
- slower setting
*what can decrease the setting time of model and die material
potassium sulfate
*what can increase the setting time of model and die material
borax
What is type 1 plaster and stone*
impression plaster
What is type 2 plaster and stone*
model plaster
What is type 3 plaster and stone*
laberatory stone
What is type 4 plaster and stone*
die stone
