robbypowell's version from 2016-10-30 18:09

impression materials

Question Answer
Define:________ is Based on the ability to of an impression material to recover from deformationElasticity (alginate, PVS yes.... wax or ZOE no)
Define:________ time: amount of time from beginning of mix until end of mix where it is ready to be placed into a delivery device (tray, syringe).MIXING time
Define:________ time - amount of time allowed to place material into delivery device, take it to the mouth, and extrude/position it.WORKING time
Define:________ time - amount of time from placement in the mouth until the product has cured and is ready for removal.SETTING time
Define:_______ _______- ability of an impression material to faithfully reproduce the dimensions of the structures it is to capture.DIMENSIONAL ACCURACY
Define:_______ _______ - the ability of an impression material to maintain its dimensional accuracy over a given time.DIMENSIONAL STABILITY
Define: ________ = dispersion of small, microscopic particles in a liquid. These particles are macromolecules or clusters of small molecules. Due to Brownian motion, the particles will not drop out of solution to the bottom of the liquid as would a suspensionColloid
Define: ________ = The internal resistance offered by a material to flow of its molecules.Viscosity
_____ is added to agar hydrocolloid for body and strengthBorax (Na2B4O7 • 10 H2O)
To get agar hydrocolloid from solid (gel) to liquid (solution) what temperature is necessary?boiling temp (212 F; 100 C)
Prior to placement in the mouth, Agar Hydrocolloid is extruded into a tray and tempered shortly to ____ deg C to reduce thermal shock to the patient45° C
For Alginate Hydrocolloid, When mixed with water, gypsum goes into solution and releases _____ ions. These ions preferentially interact with ______ ____ and allow for a delay in the primary settingCalcium; Trisodium Phosphate (TSP)
Manufacturers adjust the working time of Alginate by adjusting the amount of ______ in the materialTSP (Trisodium phosphate)
This type of impression material has a brown paste and a white paste that are mixed togetherRubber base (polysulfide) (paste/paste)
for rubber base polysulfide materials... the brown paste acts as the _____ while the white paste has the polymerizing componentsAccelerator
define: a group of compounds in which silicon atoms are bound to both oxygen atoms and organic groups (organic-silicon-oxygen)Siloxanes
What are the components of the materials in the two tubes for PVS materials?1) pre polymerized silicone with only si-H terminating groups 2) pre-polymerized silicone with (C=C) groups plus chloroplatinic acid catalyst
The catalyst paste of polyethers contains a cross-linking agent that is an aromatic _____ _____ ____Sulfonic acid ester
Define: ________ is the the ability of a material to interact with waterWettability
Materials that are hydro-_____ will displace blood, saliva and oral fluids, decreasing the occurrence of voids in the impression from these components.Hydrophilic
Hydro-______ materials will not displace oral fluids, and thus will leave voids where fluids were.Hydrophobic
Hydro-_____ materials will have enhanced ability to pour die stone into impression without getting bubblesHydrophilic
Hydro-_____ materials are difficult to pour with aqueous-based stones without trapping bubbles.Hydrophobic
High or low viscosity desired for capturing hard oral structuresLow (Clinically, what is desired is a low viscosity material covering the area of interest, then coverage by a higher viscosity material that will exert force on the low viscosity material to force it to be in intimate contact with tissues)
_____ rate is the Rate at which molecules slip and slide past one anotherShear rate
_____ rate is applicable during material injection or tray seating of impression materialShear rate (affects viscosity)
Non-Linear and tremendous increase in viscosity as shear rate increases: is a property of ____ fluidDILATANT
Linear change in viscosity as shear rate increases: is a property of ______ fluidNEWTONIAN fluid
Great decrease in viscosity as shear rate increases: is a property of ______fluidPSEUDOPLASTIC fluid
viscosity decreasing as an impression material is delivered from a syringe tip or when tray is seated is termed _____ _____Shear Thinning
Uni-compositional (uni-viscosity) impression materials are termed _______. The advantage of these materials are that they can have a high degree of body so that they do not fall out of the impression tray, and yet they can flow easily when expressed through the syringe or when the tray is seated.thixotropic
Excess fluids exude out of agar hydrocolloid over time; a process referred to as _______.syneresis
what material sets by a VULCANIZATION reaction (much like the way tires are made)Polysulfide (rubber base)
Rubber-base... would it set at tooth surface or impression tray first?Tooth surface (higher temps and water speed up rxn)
What elastomeric material has the highest shrinkage (0.5-1.5%)Polysulfide
the lowest shrinkage is associated with what material? (0.05%)PVS
T/F: PVS rxn is sped up by the presence of moisture and temperatureFalse (There is no evidence of sensitivity with this setting reaction to either moisture or to temperature.)
Rank PVS, polysulfides and Polyethers in terms of shrinkage, greatest to leastPolysulfide (rubber base) > Poly-ether > PVS
What is the purpose of tray adhesivecreate uniform shrinkage due to "guided distortion" (toward tray)
type of disinfection suggested for polyetherspray (1:10 dilution of clorox bleach)
this impression material can release hydrogen gas after setting, so pouring up should be delayed to stop from adding bubbles to stone and weakening itPVS
what material has the highest tear strength?Rubber-base
preferred method of disinfecting alginate impressions?Spray disinfectant (bleach)
agar hydrocolloid can be kept in liquid form indefinitely if kept at _____ degrees celsius65


Question Answer
is it hydrophobic or hydrophilic?
rubber basephobic
alginate hydrocolloidphilic
agar hydrocolloidphilic

lab info

components of alginate

Question Answer
this component is used for its calcium ionGypsum
this component will provide working timeTrisodium phosphate
this component counteracts the inhibiting effect of borax which tends to retard setting of the stone against the impressionPotassium sulfate
this component adds strength, but also retards setting time of stoneBorax
this component of alginate is the fillerDiatomaceous earth

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