841. Microfilled composites contain filler particles with diameters in the range of ?
A. 4 -20 um
B. 0.04 -0.06 um
C. 20 -80 um
D. 0.8 -6 um
842. Poly (methyl methacrylate) resin despite having a high volumetric curing shrinkage, can be used toproduce clinically satisfactory dentures because?
A. shrinkage will be distributed uniformly over all surfaces of the denture
B. when packed under pressure the shrinkage will be reduced to acceptable levels
C. the separating media used, reduces the shrinkage
D. the heat employed in polymerization reduce the shrinkage
843. When restoring a cavity with direct filling gold, transverse strength and density would be greater,when?
A. combination of mat gold and electrolytic gold are used
B. powdered gold is used alone
C. gold foil is used alone
D. combination of mat gold and gold toil are used
844. When curing dentures, the surface or subsurface porosities occurring with the fluid resintechnique, are commonly due to?
A. lack of adequate pressure during polymerization
B. failure to expel air inclusions incorporated during pouring of the resin
C. lack of homogeneity in the dough or gel
D. a definite lack of dough or gel in the mold at the time of final closure
845. Of the following, the most ductile metal is?
846. A desirable characteristic of Type ll (Type B) inlay waxes used in the direct technique is that, they should?
A. have a color which matches that of the tooth
B. have a flow of less than 1% at 37°C
C. have a flow of at least 50% at 45`C
D. have a high coefficient of thermal expansion
847. Which of the following methods of manufacturing results in the hardest type of dental stone?
A. Calcining gypsum in open vats
B. ‘Calcining gypsum in a 30% solution of calcium chloride
C. Direct mining from the earth
D. Calcining gypsum in a pressure pot under 20 lbs/inch2 pressure
848. The strength of zinc oxide -eugenol cements can be substantially increased by?
A. increasing the spatulation lime
B. the addition of orthoethoxy benzoic acid
C. using a lower powder/liquid ratio
D. addition of a drop of water to the mix
849. Color matching should be done under two or more different light sources because of thephenomenon of?
D. eye fatigue
E. Munsell effect
850. How many calories of heat are required to vaporize 1 gm of water at 100°C?