1001. The attraction between atoms or molecules because of van der Waals forces is due to?
A. magnetic oscillations
B.a static electron field
C.a fluctuating dipole
D.the sharing of a valence electron
1002. Which of the following is formed when gypsum is calcined at temperatures 500°C?
A. Orthorhombic anhydrite
B.Calcium sulfate dihydrate
C. Calcium sulfate hemihydrate
D. Hexagonal anhydrite
1003. The filler used in impression compound is?
A. bees wax
E.zinc phosphate powder
1004. Which of the following impressions can be most safely transported to the dental laboratory?
1004. The flux used when casting gold alloys?
A. helps to prevent oxidation of the alloy
B.contains borax and boric acid
C.increases fluidity of the metal
D.all of the above
E.none of the above
1005. Lattice imperfections of metal structures, in which a lattice position is left vacant, are termed ?
A. interstitial point detects
1006. Gold alloys used for the fabrication of saddle bars and clasps, are?
A. Type I
1007. The plasticizer commonly used in non-aqueous elastomeric impresion materials is?
1008. Denture cleansers which clean by liberating oxygen, contain?
A. sodium chloride
1009. The average particle size of modern dental amalgam alloys is?
A.0.05 -0.9 micrometer
C.100 -140 micrometer
D. 25-35 micrometer
1010. Concentrations higher than 50% of phosphoric acid are not used for acid etching, as this would?
A. form a protective layer on enamel which protects the tooth from further dissolution
B.lead to massive decalcification of enamel rods
C.damage the pulp
D.make the etching process too fast to comfort