951. Direct tilling gold contains?
A. more than 90% pure gold
B.70.85 % gold
C.99.99% pure gold
D.more than 65% gold

952. Tarnishing of amalgam restorations is due to the formation of?
A. silver sulfide
B. tin oxide
C.silver halide
D.copper sulfide

953. Which of the following terms can aptly describe alginate impression materials?
A. Thermoplastic
D.Irreversible elastic
E.Reversible plastic

954. Human teeth possess which of the following hue portions of the color spectrum?
A. Yellow and yellow-red
B.Red and yellow-red
C.Green and yellow-green
D.Yellow-red and yellow-green
E.Red. green, and blue

955. The oxidizing agent used in the polymerization of polysulfide impression materials is?
A. lead peroxide
B.tin octate
C.lead octate
D.stannous octate
E.copper phosphate

956. Growth of secondary dentin is best stimulated by?
A. composite resin cements
B.zinc phosphate cements
C.zinc oxide-eugenol cements
D.calcium hydroxide cements
E.Carboxylate cements

957. Which of the following atomic bonds are characterized by physical forces?
A. Ionic bonds
B.Van der Waals bonds
C.Metallic bonds
D.Primary bonds
E.Covalent bonds

958. A reusable impression material is?
A. impression plaster
B.non-aqueous elastomers
C.zinc oxide eugenol
D. alginate hydrocolloid
E. impression wax

959. During the calcining of gypsum?
A. it is subjected to temperatures of 110 to 120°F
B.part of water of crystallization is deriven off
C.silica is added
D.it is boiled in distilled water
E. all of the above

960. Amongst the non-aqueous elastomeric impression materials curing time is longest for the?
B.condensation silicones
D.addition silicones