641. The setting time of irreversible hydrocolloids can be decreased by_____________?
A. Raising the temperature of water used for maxing
B. Lowering the temperature of water used for mixing
C. Using excess water for maxing
D. None of the above

642. Rubber base impressions are poured immediately as they_______________?
A. Continue to polymerize
B. Show imbibition and syneresis
C. Become elastic
D. Show gelation

643. The most mucostatic impression material is_______________?
A. Thin mix of plaster of paris
B. Free flowing wax
C. Zinc oxide eugenol impression paste
D. Reversible hydrocolloids

644. The best way to remove a hydrocolloid impression from the patient’s mouth is____________?
A. Wetting the periphery of the impression with moist cotton to break the peripheral seal
B. Slight rocking of the impression to disengage it from the undercut
C. Sudden jerking of the impression to prevent tearing
D. Supporting the impression along with the tray to prevent disengaging of the tray alone

645. Palatal secretions affect the setting of all the impression materials except_______________?
A. Impression paste
B. Agar-agar
C. Silicone
D. Impression plaster

646. Lenolin is added is ZOE paste to______________?
A. Accelerate reaction
B. Increase flow
C. Decrease flow
D. Decrease irritation due to eugenol

647. Agar is prepared from_______________________?
A. Chemicals
B. Bullock heart
C. Sea weed
D. Chick cells

648. Perforated impression tray are used for_______________?
A. Alginate
B. Agar-agar
C. Zinc oxide-eugenol
D. Impression compound

649. During setting of alginate impression materials________________?
A. Colloidal changes to sol
B. Trisodium phosphate reacts with calcium sulphate
C. Trisodium phosphate reacts with sodium alginate
D. Material in contact with soft tissues sets last

650. K2SO4 in agar-agar is for_______________?
A. Accelerating the setting stage of gypsum
B. Give dimensional stability
C. Increase strength
D. None of the above