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FINAL: Accurate Alginate Impressions and Diagnostic Casts (DENT 106)
Terms in this set (45)
Gypsum Type I
impression plaster (low expansion)
Gypsum Type II
Gypsum Type III
Gypsum Type IV
dental stone/ densite/ die stone (lowest expansion)
Gypsum Type V
die stone / densite high expansion (highest expansion)
What is the active ingredient in irreversible hydrocolloid?
Which type of gypsum has the least gauging water:
Type 5, die stone high strength/high expansion (alternative: Type IV densite)
Which type has the least expansion:
Gypsum products are the same chemically and differ only in particle size and shape.
Irreversible hydrocolloid cross sectional thickness=
Elastomeric materials (PVS) are best at
Which of the following materials are elastomeric?
Polysulfide rubber, condensation silicone, addition reaction silicone, polyether rubber
Alginate impressions should be poured within
Let gypsum casts with alginate impressions set for
Type I gypsum =
Primary constituent of an alginate impression iswater
Primary constituent of alginate is
What type of gypsum is best for mounting casts in an articulator?
Impression plaster (Type I) because it sets quickly and does not have time to expand
Which material has the best abrasion resistance?
Densite (Type IV)
Which material has the least amount of gauging water?
Densite (Type IV) and Die Stone (Type V)
Used to make precision die?
Densite (Type IV)`
Which type of gypsum material is used for fabrication of dies?
Relative humidity is a factor in
Which of the following materials is truly hydrophilic?
What are most diagnostic casts made out of?
Type 3/dental stone/hydrocal
Type 5 gypsum is also called?
Die stone high expansion
Mineral gypsum is mined as
calcium sulfate dihydrate
You need the least gauging water for
Type 4/densite/improved dental stone
What does ADA Spec #25 specify as the level of fine detail recording for gypsum products?
50 microns (PVS gives the best reproduction, but the limiting factor is gypsum die)
As with alginate (irreversible hydrocolloid), the most important part of making a good gypsum cast regards:
Accurate water/powder ratio
Alginate (irreversible hydrocolloid impression material) needs fine detail reproduction of only:
Why doesn't type 1 gypsum expand very much?
Sets very quickly
Individual stone dies to make wax patterns made out of?
Densite (type 4)
Die for fabricating metal ceramic crowns:
Type V gypsum (die stone)
Which of the following sets by a polymerization reaction?
Polysulfide rubber, irreversible hydrocolloid, and condensation silicone (NOT impression compound or reversible hydrocolloid)
Alginate impressions should be separated from the gypsum cast between 45-60 minutes after pouring to:
allow the gypsum to attain adequate strength for removal, prevent interaction of the water in the impression with the gypsum, improve surface of gypsum cast (B, C, D)
Which of the following statements is true regarding custom trays, stock trays, and elastomeric impression materials?
Studies indicate that impression materials in custom trays are more accurate
Impression procedure is more comfortable for the patient with a custom tray
Impression materials costs are less with custom trays
Appropriate adhesive should be used
Occlusal stops with custom trays:
Are needed to ensure that the tray is orientated correctly in the patient's mouth
Should be placed on non-functioning cusp tips
Ensure a uniform cross-sectional bulk
Which of the following statements are true regarding custom trays?
1 - 2 mm (not 4 - 6 mm)
Must be rigid
Must be stable
Assuming the water/powder ratio is 50 cc / 10 gm, and 19 ccs of water chemically react with gypsum power, the amount of gauging water is
Mineral gypsum heated in an open container will produce
Mineral gypsum heated under pressure will provide
ADA spec for Silicone =
25 microns or less
ADA spec for Alginate =
75 microns or less
Does gypsum expand or shrink when it sets?
Expands (more gauging)
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