821. An elastomeric impression will be more accurate if it is?
A. removed as soon as it sets
B. removed after 8-10 minuted
C. allowed to remain in the mouth for a longer time
D. time in mouth is not critical for accuracy
822. An alloy is a solid mixture of?
A.two or more metals, one at which it mercury
B. three or more metals. one of which is gold
C.two or more metals
D. two or more metals, one of which is amalgam
823. Methyl methacrylate based denture base resins contain all of the following. Except?
A. glycol dimethacrylate
B. dibutyl phthalate
C. benzoyl peroxide
D. pure methyl methacrylate
E. sodium silicate
824. When mixing dental stone, if the water-powder ratio is increased, the?
A. compressive strength is increased
B. surface hardness is increased
C. setting time is decreased
D. setting expansion is decreased
825. What is the name given to the technique in which acrylic resin is softened by heat and introduced into flasks under pressure?
A. Fluid resin technique
B. Vacuum molding technique
C. Compression molding technique
D. Pressure technique
E. Injection molding technique
826. Following casting, the gypsum mold is quenched in water when the button emits a
A. dull red glow
B. cherry red glow
C. lightorange glow
D. dull grey glow
827. Which ingredient is added to Inlay wax to improve its smoothness during molding ?
A. Paraffin wax
B. Gum dammar
C. Candelilla wax
D. Carnauba wax
828. When making an impression, the impression compound should be placed in the patient’s mouth at
829. Sometimes a die larger than the prepared tooth is desired, to aid in compensating for the .
A. casting shrinkage of the alloy
B. dimensionalchange of the impression
C. warpage of the wax pattern
D. expansion of the mold
830. The phosphate investment clinging to base metal castings is cleaned by?
A. dipping in cold hydrofluoric acid
B. grinding with a bur or stone
C. heating in hydrochloric or sulfuric acid
D. sand blasting