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WorksheetsGypsum Product - Final
Total questions: 20
Worksheet time: 15mins
Which gypsum product has the highest surface hardness?
(a)What is the main purpose of adding potato starch to impression plaster?
Better dimensional stability
Easy separation of cast from the impression
More accurate impression
Prolong the working time
The α & β hemihydrates differ mainly in terms of thei
(a)Setting of die stone is the result of
Difference in the solubility of CaSo4 . ½ H O & CaSO4.2H O
Nucleation & growth of CaSo4 . ½ H2O crystals
Precipitation of CaSo4 . ½ H2O crystals
Reaction between CaSO4 .2H2O and water
The strength of gypsum products is generally expressed in terms of
(a)Dental plaster
(a)The main reason why higher water: powder ratio should be avoided during manipulation of die stone is, because it
(a)An increase in the no. of nuclei of crystallization will result in
Higher strength
Higher setting time
Lower setting expansion
Lower surface hardness
Gillmore needles are used to measure
Setting expansion
Setting time
Strength
Surface hardness
What is the setting time of dental stone in minutes?
4±1
8±2
12±4
16±6
Which gypsum product has lowest strength?
Densite
Dental plaster
Hydrocal
Impression plaster
Which is the best way to increase the working time of densite?
Adding borax
Adding potassium sulfate
Faster spatulation
Using higher water:powder ratio
Addition of potassium sulfate to dental plaster
Decreases rate of setting reaction
Increases setting expansion
Increases the strength
Shortens working time
Which gypsum product is strongest?
Type II
Type III
Type IV
Type V
Finer the particle size of dental stone
Higher is the strength
Lower is the setting expansion
Lower is the solubility in water
Slower is the setting reaction
Gypsum products are considered ‘BRITTLE’ as their tensile strength is much lower than their compressive strength
True
False
Balanced gypsum products contain accelerator & retarder in equal proportions.
True
False
Dry strength of gypsum products is always more than wet strength
True
False
Chemical modifiers are added to gypsum products to control the rate of setting reaction.
True
False
Water: powder ratio is the amount of water (in ml) added to 100g of powder to convert the hemihydrate to dihydrate.
True
False
