Gypsum Questions with complete solution 2024/2025 Gypsum & Wax Products
Intro - correct answer - Gypsum has been used to make diagnostic dental casts since 1756
- RDHs are usually called upon to produce casts, which are also useful for presenting pt education
- Production of gypsum cast...
Gypsum & Wax Products
Intro - correct answer ✔- Gypsum has been used to make diagnostic dental
casts since 1756
- RDHs are usually called upon to produce casts, which are also useful for
presenting pt education
- Production of gypsum casts requires meticulous attention to detail, a well
though out process in their production, and knowledge of the advantages and
limitations of each gypsum material for appropriate selection
Intro - correct answer ✔- Inaccurate, incomplete, or weak casts are of little
use and are likely to produce costly mistakes in pt treatment procedures
- Dental waxes are used in a wide variety of clincial and lab dental procedures
- May be used to fabricate direct waxings for cast restorations, alterations and
adaptions for impression trays and wax bite registrations
Intro - correct answer ✔- In the lab, may be used to box an impression
before pouring a gypsum product, as baseplates for full and partial dentures,
to hold components together before articulation, and to provide indirect
patterns for casting
- RDHs will frequently manipulate waxes in taking alginate impressions,
pouring impressions, and taking a wax bite registration for articulation of
models
,Uses and desirable qualities of gypsum products - correct answer ✔-
Gypsum products are used to make replicas of the pt's mouth
- Replicas are called diagnostic casts, used to plan treatment, and observe
oral structures
Diagnostic casts - correct answer ✔aka study models, are used to plan
treatment and observe oral structures
(Used extensively by orthodontists)
Working casts - correct answer ✔Used to fabricate appliances like
orthodontic retainers, bleaching trays, or a removable prosthesis like a partial
or full denture
Uses and desirable qualities of gypsum products - correct answer ✔-
Desirable quantities for each of the above are dependent on the use stresses
required by the product
- All casts and dies must be accurate, hard, and dimensionally stable under
normal conditions of use and storage
- Working casts and dies must have accurate reproduction of fine detail,
strength and resistance to abrasion, and minimal solubility
Uses and desirable qualities of gypsum products - correct answer ✔- Color is
important in identification of material and to provide contrast between die
material and waxed inlay pattern
, - Cost, ease of use, and safety are practical considerations in manipulation of
product and frequency of use
Chemical properties & behaviors of gypsum products - correct answer ✔-
Dihydrate of calcium sulfate (CaSO4 -2h2O) mined as a solid mass
- Calcination: Mineral gypsum (dehydrate of calcium sulfate) with heat under
pressure = calcium sulfate hemihydrate + water (ground into powder)
- Reverse reaction: Calcium sulfate hemihydrate + water = dihydrate of
calcium sulfate (exothermic)
Chemical properties & behaviors of gypsum products - correct answer ✔-
Components of all gypsum products are chemically the same
- Physical differences are due to difference in calcination and resulting amount
of water drawn off the dehydrate
- Production of the various forms of gypsum is basically the same, used for
several different purposes
Model plaster vs. Dental stone - correct answer ✔- Ground gypsum heated
in open vats become B-hemihydrate or model plaster (irregularly shaped and
porous) commonly used for diagnostic casts
- If heating is done under pressure, dental stone is produced (more uniformly
shaped, less porous), used for working casts
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