Impression trays and impression techniques Flashcards
which impression is used for construction of special tray ?
primary impression
what type of materials are used for primary impression ?
impression compound or alginate (flexible)
what types of materials are used for secondary impression ?
zinc oxide eugenol (rigid) or rubber base (flexible)
pouring material of primary impression :
plaster of paris
pouring material of secondary impression :
dental stone
what is the difference between stock trays used for dentulous patients and stock trays used for edentulous patients ?
- height of dentulous stock tray is greater to accommodate teeth
-edentulous tray has a protruding L shaped handle to reach into the oral cavity
-dentulous trays are square in shape while edentulous ones are more rounded
foam trays are used in :
children
which type of material is used in perforated trays ?
material requiring mechanical means of retention . COMPOUND
mode of registration ( or basically what function the patient should be doing when taking the impression ) of minimal pressure impression taking ?
at state of relative rest
which tray is used when taking a minimal pressure impression technique ?
perforated tray ( to relieve any pressure) with spacer ( customized for this specific patient)
what kind of impression material is used in minimal pressure impression technique ?
low viscosity impression material
mode of registration of muco-compressive impression technique ?
at function ( under biting force)
what kind of tray is used when muco-compressive impression technique is employed ?
non-perforated without spacer , with occlusion rims
what type of impression material is used for muco-compressive impression technique ?
viscous impression material
how is selective pressure impression technique beneficial to denture stability both at rest and during function ?
the impression is taken both at rest and under pressure depending on the area . so the denture is very well adapted for both . minimal pressure impression technique on the other hand , only takes into account the patients anatomy at rest , which is why it could be unstable when in function. muco-compressive impression technique suffers from the same issue but opposite ( stable under pressure , not stable at rest )
which impression technique covers the max area and results in better force distribution when denture is installed?
muco-compressive impression technique
Which type of material is used for perforated trays ?
alginate and rubber base
stability of a denture is dependent on ___
secondary impression
indication for minimal pressure impression :
flabby ridge
which kind of tray reduces bulk of impression material and why is this beneficial ?
special tray , this is important because it makes it possible to have uniform shrinkage
spercial tray is also :
-more comfortable for patient
-has more accurate border contour
-uses less impression material
why is thr border of the special tray 2mm short of the full depth of vestibule ?
to all for continous adaptation of border to soft tissue (peripheral seal) by allowing for modelling of impression material/ intimate contact /shaping of flexible material that wraps around
why is the process of boxing important ?
-preserves borders of impression
-thickness of base of cast can be controlled
-time and material is conserved
-permits vibrating the stone material into the impression
non perforated trays are used alongside which type of material?
materials having adhesion properties to tray
agar agar requires use of which tray ?
water cooled trays
disadvantages of using minimal pressure impression technique ?
-denture not stable at function
-sparating medium on using plaster Imp
disadvantages of using muco-compressive impression technique :
-denture not stable at rest
-continious pressure
-increases bone resorption
-decreases blood supply
advantages of selective pressure impression technique ?
-stability during both rest and function
-automatic relief
-pressure to primary bearing areas
advantages of acrylic resin special tray :(self curing)
-easily constructed
-more rigid than shellac
-accept border tracing material
-easily trimmed
advantages of using a spacer:
-allows for even thickness for impression material to rest on
-aid in relief when used with selective impression technique
