Impressions Flashcards
what is an impression?
a negative imprint of an oral structure used to produce a positive replica of the structure
used for perm. record/in production of prosthetics
what is a study model used for?
prep for treatment planning
patient construction
what impression to do first?
mandibular before maxillary
interocclusal record for occluding the casts last
stages of impression taking?
position
remove any appliances
examine oral cavity
remove any debris
alginate constituents?
irriversible hydrocolloid
carboxylate polysaccharide based on alginic acid
gels by cross linking formation with calcium ions
sodium alginate
calcium phosphate
sodium phosphate - retarder
fillers e.g zinc carbonate
pH indicators - changes colour, pH drops as gels
alginate mixing?
powder deteriorates on standing
water at room temp - ideal gelation time between 3-4 mins = adequate working time
spatulation - 1 min allows chemical reaction to proceed uniformly
working time = 30 seconds
load tray one end to other
tray selection?
suitable length to cover retromolar region area of mandible and tuberosity of maxilla
clearance anteriorly to most protruding incisor
too wide = may impinge on lingual/palatal cusps of molars
insert tray with what motion?
ask pt to lift?
rotary motion
tongue
take mandible from where?
in front of
take maxilla from where?
behind pt
seat where first when taking maxillary?
seat posterior before anterior
precoat what areas?
precoat potential areas of air entrapment
what is used to disinfect?
sodium hypochlorite with no distortion -5-10mins
actichlor - ten tabs to 1/litre of water
immerse 2 mins
rinse
what is the interocclusal record?
registration of normal positional relationship of opposing teeth/dental arches made in plastic material - soft wax
how to take interocclusal record?
shape a double layer of wax in the form of an arch, soften in warm water, place over maxillary occlusal surfaces
guide pt to habitual occlusion
