Kerala University 2009 B.D.S Dental Surgery , 3, Dental materials - Question Paper

b) GIC
c) polycarboxylate cement
d) zinc-oxide eugenol cement
13. Material having coefficient of thermal expansion similar to that of the tooth enamel
a) composite
b) amalgam
c) kind II GIC
d) direct filling gold
14. Strength in gypsum investment is given by
a) quartz
b) dental stone
c) silica
d) tridymite and cristoballite together
15. Component of inlay wax that contributes more to the glossiness of the wax surface
is
a) paraffin wax
b) gum dammar
c) carnauba wax
d) candelilla wax

PA RT – B
(Prosthodontics)
Time : 11/2
Hours Marks : 50

I. describe soldering and welding. Enumerate the desirable qualities of an ideal solder.
Write in detail about investment soldering and free hand soldering techniques. one 0

II. Write the composition and setting reaction of irreversible hydrocolloid impression
material. provide the causes and remedies for various kinds of failure encountered
with the use of irreversible hydrocolloid impression material. one 0

III. Write short notes on : one 5
a) Viscosity.
b) Galvanic corrosion.
c) Separating medium.

IV. Multiple option ques. : one 5
1) Increasing the Water-Powder ratio of dental stone would
a) Increase the setting expansion
b) Increase the 1-Hr compressive strength
c) Lengthen the setting time
d) reduce the amount of excess water used to mix the material
2) The setting time of zinc oxide eugenol impression paste can be prolonged by
a) Mixing for a longer time
b) Adding chemical modifier, zinc acetate
c) Decreasing the amount of base paste
d) Cooling the glass slab and spatula not beneath the dew point

The main purpose of adding butadiene styrene rubber to acrylic resin is to
increase its
a) Impact strength
b) Compressive strength
c) Tensile strength
d) Shear strength

4) Cristobalite is a high expansion form of
a) SiO2
b) Al
2
O3
c ) K2
O d) Na
2
O

5) The yield stress of metals can be improved by
a) Chemical tempering
b) Transformation toughening
c) Thermal tempering
d) Work hardening

6) Crazing of dentures occurs as a outcome of
a) Relaxation of internal surface stresses
b) Lack of conduction of heat from inside to outside
c) Lack of adequate pressure
d) Leaching out of the plasticizer

7) Agar hydrocolloid gel should be liquefied by heating at
a) 37° C b) 45° C c) 65° C d) 100° C

8) The boiling point of methyl methacrylate monomer is
a) 100.8° C b) 180.1° C c) 108.0° C d) 108.8° C

9) Hardness of which of the subsequent abrasives is maximum ?
a) Sand b) Emery
c) Boron carbide d) Silicon carbide

10) What is a wrought metal ?
a) When metal is worked in cold state
b) When metal is heated and then cooled
c) When copper is added to a metal
d) When more than 2 metals are mixed in molten state

11) Siliconized alginates have better
a) Impact strength b) Transverse strength
c) Tear strength d) Fatigue strength

12) Phenol and formaldehyde are polymerized to a resulting product known as
a) Vulcanite b) Bakelite
c) Cryolite d) Cellulose nitrate

13) In which of the subsequent hardness tests, hardness is measured as the depth of
penetration
a) Brinell b) Rockwell
c) Vickers d) Knoop

14) The binder used in gypsum bonded investments is
a) Sodium phosphate
b) Ethyl silicate
c) Calcium sulfate alpha hemihydrate
d) Ammonium phosphate

15) Hardness of elastomers is measured by using
a) Oscillating rheometer
b) Shore a durometer
c) Vicat penetrometer
d) Gillmore needle

Earning:   Approval pending.