411. In plaster of paris the setting time is primarily altered by_________________?

A. Altering P / L Ratio
B. Altering temperature of mixing water
C. Speed and length of hand spatulation
D. Addition of accelerators and retarders

412. Which is gypsum product_______________?

A. Stone
B. Plaster
C. Investment
D. All of the above

413. The most commonly used accelerator in gypsum product is___________________?

A. Sodium fluoride
B. Potassium fluoride
C. Potassium sulfate
D. Aluminium sulfate

414. The hygroscopic technique is associated with______________?

A. Investment
B. Hydrocolloids
C. Amalgam
D. Silicate

415. Accelerators and retarders are used with gypsum products mainly to control_______________?

A. Setting time
B. Setting expansion
C. Hardness of the set product
D. None of the above

416. The main ingredient in dental plaster in_______________?

A. Calcium sulphate hemihydrate
B. Calcium phosphate
C. Calcium anhydrate
D. Calcium sulphate dihydrate

417. Die is________________?

A. Impression of single tooth
B. Impression of whole teeth
C. Replica of single tooth
D. Replica of whole teeth

418. Plaster of paris is mixed in________________?

A. Plastic bowl
B. Rubber bowl
C. Glass bowl
D. Metal bowl

419. Water of reaction needed to react completely with 100 g of calcium sulphate hemihydrates to convert it to calcium sulphate dihydrate______________?

A. 18.6ml
B. 22.2ml
C. 30.4ml
D. 45.3ml

420. Green strength with reference to plaster means_____________?

A. Dry strength
B. Compressive strength
C. Strength of dental stone due to green colour
D. The wet strength


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