MCQs on Dental Materials - Metallurgy

# All of the following statements about cast cobalt alloys are true EXCEPT:
A. They have a modulus of elasticity twice that of gold alloys
B. They are more rigid than gold alloys
C. They have higher ductility than gold alloys
D. They have a lower proportional limit than gold alloys

# The contraction of gold alloys on solidifying is approximately:
A. 0.4%
B. 1.4%
C. 2.4%
D. 3.4%

# Addition of large amounts of platinum to a casting gold alloy will:
A. Decrease its strength and ability to be hardened
B. Decrease its tarnish resistance
C. Increase its fusion temperature
D. Redden the alloy

# The pattern for the metallic framework of a removable partial denture is fabricated from:
A. Inlay wax type-II
B. Boxing wax
C. Modelling wax
D. Casting wax

# Ideal requirement of metal-ceramic casting:
A. Low fusing ceramic and high fusing alloys
B. Matching of coefficients of thermal expansion of ceramics and alloy
C. Bonding between ceramic and alloy
D. All of the above

# Gap between true end of casting ring and wax pattern should be:
A. 1/4 inch
B. 1/2 inch
C. 3/8 inch
D. One inch

# Which of the following is correct:
A. Type I and Type II gold can be heat treated and annealed
B. Type III and Type IV gold can be heat treated and annealed
C. Type I and IV gold can be heat treated and annealed
D. All the type of gold can be heat treated and annealed

# What is the use of boxing an impression:
A. Ease of construction of denture
B. Preserving the sulci
C. Ease of pouring an impression
D. All of the above

# The strength of a gypsum investment is dependent on:
A. Carbon content
B. Silica content
C. Gypsum
D. Copper

# Resistance to corrosion in a cobalt-chrome casting is due to presence of:
A. High quality iron
B. Chrome
C. Cobalt
D. Nickel

# The main form of iron carbide found in 18-8 steel:
A. Martensite
B. Ferrite
C. Austenite
D. Pearlite

# Flux is used during casting to:
A. Remove the oxides formed on the gold alloy
B. Lower the melting point
C. Replace casting wax
D. Speed the burnout process

# NiTi alloys have:
A. Shape memory
B. Hyper rigidity
C. Corrosion resistance
D. Weldable properties

# The maximum carbon content of steel used in dentistry is:
A. 19%
B. 2%
C. 1.7%
D. 4%

# Pickling:
A. Is accomplished by soakirng the casting in baking soda
B. Causes porosity in gold
C. Removes surface oxides from gold castings
D. Remove investment from gold casting

# Wax pattern is ideally invested immediately to decrease the dimensional changes caused by:
A. Decrease flow
B. Continuous expansion
C. Relaxation of the internal stresses
D. Water loss

# Bending orthodontic wire at room temperature is an example of:
A. Tempering
B. Work/ Strain hardening
C. Age hardening
D. Precipitation hardening

# The most commonly used Titanium alloy for dental and medical purposes is:
A. Ti 6Al 4V
B. Ti 5Al 4V
C. Ti 5Al 5V
D. Ti 6Al 6V

# A thinner mix of a gypsum-bonded investment will:
A. Produce a smoother casting
B. Decrease setting expansion
C. Increase setting expansion
D. Increase thermal expansion

# Cobalt-Chromium alloys contains:
A. 30% cobalt and 60% chromium
B. 60% cobalt and 30% chromium
C. 1 % palladium
D. 20% gold

# Which one of the following is most elastic?
A. Alpha titanium
B. Beta titanium
C. Chrome-cobalt-nickel
D. Nickel titanium

# Gypsum bonded investment should not be heated over:
A. 700°c
B. 1300°C
C. 1063°C
D. 900°C

# Cleaning of base metal alloy is done by:
A. Warm HCl
B. Cold HF
C. Cold H2S04
D. Sand blasting with aluminium oxide

# Glossy smooth margins of a casting are due to:
A. Shrinkage of alloy on cooling
B. Investment breakdown
C. Incomplete wax elimination
D. Incomplete gas elimination

# Which of the following zones is used for melting alloy during casting?
A. Reducing flame
B. Oxidizing flame
C. Green flame
D. All of the above

# Incomplete casting is the result of:
A. More porous investment in the mould
B. Narrow sprue diameter
C. Hollow sprue pin
D. Large reservoir

# Back pressure porosity can be avoided by:
A. Using asbestos liners
B. Placing the sprue at least one quarter inch away from the end of casting ring
C. Preventing rapid heating the investment in burnout oven
D. Using a short and wide sprue

# Mouth temperature waxes are:
A. Iowa wax
B. Modeling wax
C. Green stick wax
D. None of the above

# Setting expansion is advantageous in:
A. Casts
B. Models
C. Investment
D. Dies

# Tempering of steel cause:
A. increases its toughness
B. increases hardness
C. increases ductility
D. decreases its toughness

# Indium in metal alloys:
A. Improve bonding
B. Harden the metal ceramic Ag-Pd alloy
C. Both A and B
D. None of the above

# In a patient with allergy to costume jewelry, which of the following is contraindicated:
A. High gold
B. Low gold
C. Palladium - Ag
D. Ni - Cr

# Which of the following will produce the most rigid restoration for framework of same dimension?
A. Wrought alloy
B. Palladium alloys
C. Cobalt-chrome alloys
D. Partial denture casting gold in hardened condition

# Turbulence of molten gold is due to:
A. Impurities in gold
B. Improper venting
C. A and B
D. None of the above

# Apart from composites and ceramics, another material that could be copy milled easily and inexpensively is:
A. Molybdenum
B. Germanium
C. Titanium
D. Chromium

# A highly polished surface on a metallic dental restoration aids considerably in the prevention of the:
A. Dimensional change
B. Thermal conductivity
C. Warpage
D. Tarnish and corrosion

# Austenite is an alloy of iron and carbon with the iron in:
A. Alpha form
B. Beta form
C. Gamma form
D. None of the above

# The yield strength of Austenite (NiTi alloy) is:
A. 100 Mpa
B. 240 Mpa
C. 560 Mpa
D. 700 Mpa

# Which zone is the hottest and efficient burning zone of the flame used for casting?
A. Oxidizing zone
B. Reducing zone
C. Combustion zone
D. None of the above

# Stabilization of stain less steel is achieved by adding:
A. Carbon
B. Chromium
C. Nickel
D. Titanium

# Localised shrinkage porosity is seen when there:
A. Thin sprue
B. No reservoir
C. Investment heated strongly
D. Inadequate air discharge

# The function of a sprue is to:
A. Form an opening for molten metal to enter the mold
B. Help polish cast restorations
C. Eliminate air bubbles on the wax pattern
D. Reproduce fine detail

# Sub surface porosity can be decreased by:
A. Decreasing the sprue length
B. Decreasing the sprue thickness
C. Increasing the melting temperature
D. Increasing the mould temperature

# Softening heat treatment of alloy increases:
A. Tensile strength
B. Proportional limit
C. Ductility
D. Hardness

# The inlay wax most commonly used for direct technique:
A. Type 1
B. Type 2
C. Type 3
D. Type 4

# Reduction in the fusion temperature of dental gold casting alloys is caused by presence of:
A. Platinum
B. Copper
C. Silver
D. Gold

# The purity of gold is expressed in:
A. Carats
B. Percentage
C. Fineness
D. Gram

# Function of carnauba wax:
A. To provide a smooth and glossy surface
B. Increase toughness
C. Decrease toughness
D. Decrease flow at room temperature

# In a metal ceramic crown for a FPD the function of tin, indium which are readily oxidized minor constituents is to:
A. Improve bonding
B. Decrease porosity
C. They react with the porcelain opaque layer, which masks the metal
D. Improves the thermal expansion between the metal and porcelain

# The porosity formed due to simultaneous nucleation of solid grains and gas bubbles at the first moment that metal freezes at the mold walls is called:
A. Pinhole porosity
B. Gas inclusion porosity
C. Micro porosity
D. Subsurface porosity

# Investment material used for cobalt-chromium alloys is:
A. Gypsum bonded
B. Phosphate bonded
C. Silica bonded
D. None of the above

# The standard perforated tray for use with alginate impression materials may be brought to more customized contour by:
A. Utility wax
B. Base plate wax
C. Beading wax
D. Boxing wax

# Silica sol:
A. Is applied to the walls of the investment to produce hygroscopic expansion
B. Increase the strength and the setting expansion of the phosphate-bonded investments
C. Acts as a retarder in the silica bonded investments
D. Acts as a refract ory in the silica bonded investments

# The base constituents of dental waxes come from three main sources except:
A. Animal
B. Mineral
C. Insect
D. Vegetable

# Boxing wax is also called as:
A. Carding wax
B. Inlay wax
C. Utility wax
D. Sticky wax

# Stainless steel is used mostly in dentistry:
A. To strength amalgam
B. In orthodontic wires
C. To construct clasps for partial dentures
D. To replace internal gold restorations

# Shape memory in NiTi is because of stress induced form:
A. Austenite to martensite
B. Martensite to austenite
C. Ferrite to austenite
D. Austenite to ferrite

# A common electrolyte used for plating copper in direct dies is:
A. Copper cyanide
B. Ionic copper
C. Acidic copper sulfate
D. Silver cyanide

# Casting shrinkage is compensated by:
A. Thermal expansion
B. Hygroscopic expansion
C. Wax expansion
D. All of the above

# Waxes are used for:
A. Primary impression
B. Corrective impressions
C. Impression of single tooth
D. None of the above

# The gold alloys used for casting contain at least _______ percent of precious metal according to ADA specification number 5:
A. 55
B. 65
C. 75
D. 85

# Passivating alloys are:
A. Cr, Al, Ti
B. Cr, Mo, Ti
C. Cr, Gold, Ti
D. Cr, Fe, Ti

# Impurities in casting is removed by:
A. Annealing
B. Degassing
C. Pickling
D. Conditioning

# Which of the following refractory is used to counteract most of the expansion?
A. Quartz
B. Cristobalite
C. Tridymite
D. Corundum

# Shape memory is seen in:
A. Stain less steel wire
C. TMA wire
D. Aluminium

# Crucible indicated for casting base metal alloys is:
A. Carbon crucible
B. Clay crucible
C. Quartz crucible
D. High melting plastic crucible

# The best pickling solution for gypsum bonded investment is:
A. Hydrochloric acid
B. Nitric acid
C. Sulphuric acid
D. Phosphoric acid

# Heat hardening is the process done at:
A. Heating 750°C and slowly cooling to zero degrees
B. Heating quickly upto 450°C followed by sudden quenching
C. Heating upto 250°C for 15 to 30 min
D. Heating at 750° C and then quenching to room temperature

# Corrosion of stainless steel is due to formulation of:
A. Chromium carbide
B. Carbon carbide
C. Iron carbide
D. Nickel carbide

# Titanium casting is done:
A. Under vacuum in argon atmosphere
B. Under air pressme in nitrogen atmosphere
C. In specially fabricated aluminum vanadium crucibles
D. Using CAD-CAM technique

# The rapid decrease in tensile strength and increase in ductility of a wrought metal is seen in which stage of annealing?
A. Recovery stage
B. Recrystallisation stage
C. Grain growth stage
D. All of the above

# Gold content of an 18 carat alloy is:
A. 25%
B. 50%
C. 75%
D. 100%

# Which one of the following categories of dental materials has the highest thermal conductivity?
A. Unfilled acrylic plastics
B. Gold alloys
C. Porcelains
D. Zinc phosphate cements

# The sprue in wax pattern should be placed:
A. At right angle
B. At 45° angle
C. At obtuse angle
D. It depend upon type of wax pattern

# Most biocompatible material in oral cavity is:
A. Platinum
B. Palladium
C. Titanium
D. Gold

# Quartz in investment material is added for:
A. Strength
B. Expansion components for casting shrinkage
C. Decrease strength
D. Contraction

# Which of the waxes are derived from the lignite?
A. Paraffin wax
B. Inlay wax
C. Microcrystalline wax
D. Montan wax

# Inlay wax is used to:
A. Temporarily cement inlays
B. Make inlay wax patterns
C. Invest inlay patterns
D. Box models

# Silver plated dyes use an electrolytic bath of:
A. Silver fluorides
B. Silver cyanide
C. Silver bromide
D. Silver iodide

# 18-8 Stainless steel orthodontic wire has:
A. 18% Nickel 8% Chromium
B. 18% Chromium 8% Nickel
C. 18% Chromium 8% Cobalt
D. 18% carbon 8% Iron

# Suck back porosity is due to:
A. Attached impurities on undersurface of casting
B. Hot spot
C. No rapid cooling
D. Inadequate melting temperature

# Disadvantage of having a short sprue is:
A. Rapid solidification of metal
B. No place for reservoirs
C. Incomplete evacuation of gases
D. Difficulty in removing casting from investment

# Air bubbles formed on the surface of casting is probably due to:
A. Improper casting pressure
B. Improper heating of the investment
C. Improper angulations of sprue
D. Improper wetting of the wax pattern by the investment

# Who was the first person to introduce cast inlay restoration into dentistry?
A. William H Taggart
B. Buonocore
C. G.V. Black
D. Bowen

# Asbestos liner is used in a casting ring to:
A. Facilitate venting of the mold
B. Retard the heating of the investment
C. Permit expansion of the mold
D. All the above

# The main ingredient of inlay wax is:
A. Candellila wax
B. Paraffin wax
C. Carnauba wax
D. Gum dammar

# Which of the following decrease with strain hardening?
A. surface hardness
B. strength
C. proportion limit
D. corrosion resistance

# Casting flux is used to:
A. Prevent the oxidation of the metal during melting
B. Increase the melting point of the flux
C. Prevent the contamination of the metal and the liner
D. All of the above

# Suck back porosity in the casting can be eliminated by:
A. Increasing the mould metal temperature difference
B. Increasing the flow of molten metal
C. Flaring the point of the sprue attachment
D. None of the above

# Gases dissolved in molten metals are liberated when cooled giving rise to:
A. Suckback porosity
B. Gas inclusion porosity
C. Localized shrinkage porosity
D. Microporosity

# The component in very minor quantity in stainless steel that changes the properties to a maximum level is:
A. Carbon
B. Molybdenum
C. Chromium
D. Nickel

# Percentage of gold in high noble alloy is:
A. less than 25%
B. 25%
C. greater than 40%
D. 0%

# Binder used in Gypsum investment is:
A. Silica
B. Quartz
C. Cristobalite
D. Calcium sulphate monohydrate

# Which of the following is function of fluoride flux in soldering process?
A. It prevents the formation of copper oxide
B. It prevents the formation of chromium oxide or dissolves chromic oxide Layer
C. It prevents the flow of material in undesirable area
D. Increases the strength of solder

# Nickel-Titanium alloy has:
A. unreliable spring back
B. low spring back
C. minimal spring back
D. none of the above

# The deoxidizing agent added to dental alloys is:
A. Palladium
B. Silver
C. Copper
D. Zinc

# Advantage of titanium over other base metal alloys:
A. Low weight
B. Low cost
C. Low strength
D. Low melting point

# Function of wetting agents used in casting procedure is:
A. To felicitate wetting of ring liner
B. To felicitate mixing investment
C. To reduce contact angle of a liquid with wax surface
D. For better wax elimination

# The rate of tarnish and corrosion of class II cast material having VHN 200 is:
A. 0%
B. 2 to 3%
C. 5 to 10%
D. Less than 1%

# Component of inlay wax which makes it flake resistant is:
A. Paraffin
B. Carnauba
C. Gum dammar
D. Candelila

# Microstructure of cobalt chromium alloy in cast condition is:
A. fibrous
B. homogeneous
C. inhomogeneous
D. amorphous

# Within an hour after cementation of cast gold on lay patient complains of shooting pain every time the teeth comes together. Most probable explanation is?
A. Supraocclusion of restoration
B. Retained cement in gingival sulcus
C. Excess acid in mix
D. Galvanic current caused by gold onlay occluding with a large restoration

# Dendrites in cast alloys form by mechanism of:
A. constitutional superconductivity
B. constitutional supercooling
C. constitutional supergriting
D. constitutional supergraining

# Which one of the following elements is NOT added in small amount to be used as grain refiners?
A. Iridium
B. Ruthinium
C. Indium
D. Platinum

# Compared with noble metals, base metals show:
A. Increased hardness
B. Increased ductility
C. Better biocompatibility
D. Increased density

# Binder in Phosphate bonded investment is:
A. Magnesium oxide and Phosphate
B. Magnesium oxide and Phosphoric acid
C. Magnesium oxide and Monoammonium phosphate
D. Magnesium oxide and Ortho Phosphoric acid

# Mechanical properties of Commercially Titanium are similar to alloys:
A. type III and type IV gold
B. type V and type VI gold
C. type VII and type VIII gold
D. none of the above

# Which of the following fuel gases used for soldering, has the highest heat content?
A. Hydrogen
B. Natural gas
C. Acetylene
D. Propane

# The effects associated with cold working can be eliminated by a heat treatment called:
A. Age hardening heat treatment
B. Annealing heat treatment
C. Homogenization heat treatment
D. Solution heat treatment

# Which of the following increases castability of base metal alloys?
A. Tin
B. Beryllium
C. Molybdenum
D. Carbon

# With indirect spruing, which one of the following porosities can be minimised?
A. Back pressure porosity
B. localized shrinkage porosity
C. Pinhole porosity
D. Micro porosity

# During soldering, the solidus temperature of the filler material should be:
A. Greater than the substrate material
B. Lesser than the substrate material
C. Equal to the substrate material
D. Temperature not relevant

# The linear solidification shrinkage of Type IV Ni-Cr based alloys is:
A. 2.3%
B. 1.56%
C. 1.37%
D. 3%

# The solvent flux used for base metal soldering is:
A. Boric acid
B. Borax
C. Fluoride
D. Rouge

# Which of the following cast gold alloys is used for fabricating partial denture frameworks?
A. Type I - Soft
B. Type II - Hard
C. Type III - Hard
D. Type IV - Extra Hard

# In base metal alloys, corrosion resistance occurs due to:
A. Passivity
B. High fusion temperature
C. High molecular weight
D. Co-efficient of thermal expansion

# Modern dental noble metal casting alloys generally have equiaxed fine grain structures because of the incorporation of small amounts of:
A. Chromium
B. Indium
C. Iridium
D. Palladium

# The castability of chromium-cobalt base metal alloys when compared to gold based noble metal alloys is:
A. More
B. Less
C. Equal
D. Depends on the alloy type

# Nickel is added to wrought gold alloys as:
A. Strengthener
B. Hardener
C. Whitens the alloy
D. Scavenger

# Fins and spines on the casting is seen due to:
A. Prolonged heating
B. Rapid heating rate
C. Water film contamination
D. Too high pressure during casting

# Stages of annealing in order:
A. Recovery, recrystallization, grain growth
B. Recrystallization, recovery, grain growth
C. Grain growth, Recrystallization, recovery
D. Melting point, Grain growth, Recrystallization

# Solder and flux used for joining Elgiloy wires are:
A. Gold solder and borax flux
B. Gold solder and fluoride flux
C. Silver solder and borax flux
D. Silver solder and fluoride flux

# Dr. Taggart is associated with:
A. Discovery of Ceramics
B. Lost wax technique
C. Acid etch technique
D. Bleaching procedures

# Which of the following fuel gases is the best choice of heat source to carry out soldering process?
A. Propane
B. Acetylene
C. Natural gas
D. Hydrogen

# The term ordered hardening heat treatment used in which of the following dental alloys?
A. Gold-Copper
B. Nickel-Chromium
C. Nickel-Titanium
D. Silver-Palladium

# The best fuel gas when used with oxygen is:
A. Hydrogen
B. Natural gas
C. Propane
D. Acetylene

# Linear coefficient of thermal expansion of metal used for metal ceramic restoration range from:
A. 11.5-12.5x10-6/°C
B. 10.5-11.5x10-6/°C
C. 13.5-14.5x10-6/°C
D. 16.5-17.5x10-6/°C

# Annealing is also known as:
A. Soft hardening treatment
B. Hard hardening treatment
C. Precipitating heat treatment
D. Stress relieving heat treatment

# Quartz is added to gypsum bonded investment to:
A. Increase the strength
B. Counter balance contraction of gypsum during heating
C. aid in hygroscopic expansion
D. increase the shelf life of investment

# Chromium is used in stainless steel for which purpose?
A. Corrosion resistance
B. Increases the lustre of stainless steel
C. Stabilization of the alloy
D. Increases the hardness of steel

# The best bio-compatible dental casting alloy is:
A. Co-Cr
B. Ni-Cr
C. Titanium alloy
D. Gold

# Which of the following characteristics of inlay wax is its major disadvantage?
A. Flow
B. Rigidity
C. High thermal expansion
D. Low thermal conductivity

# Which among these is not an ideal property of soldering material?
A. Corrosion resistant
B. Non-pitting
C. High fusing
D. Free flowing

# Which of the following is not used as antiflux?
A. Graphite
B. Iron oxide
C. Boric oxide
D. Calcium carbonate dissolved alcohol

# Which of the following statements is not true about use of silica in the investment materials?
A. It acts as refractory
B. It regulates thermal expansion
C. Quartz and cristobalite are the allotropic form used in dental investments
D. Beta allotropic form is stable below transition temperature

# Which of the following is a solid solution?
A. Amalgam
B. Cobalt-chromium
C. Silver-palladium
D. Gallium-silver

# Laser welding:
A. Involves high heat generation
B. Can be done with pure Titanium
C. Is not used in dentistry
D. Can be done with pure gold

# Which is false regarding ethyl silicate bonded investment?
A. Silica gel which reverts to silica on heating
B. Magnesium oxide provides strength
C. It is easy to handle and most commonly used
D. On mixing ammonium chloride silica liquid converts to gel

# The component responsible for allergy in dental casting alloys is:
A. Cobalt
B. Nickel
C. Copper
D. Titanium

# Chromium added to steel does not:
A. Increase hardness
B. Increase tensile strength
C. Increase corrosion resistance
D. Decrease elastic limit

# The casting shrinkage in gold alloys is maximum in:
A. Class II MOD inlays
B. Large class V restoration
C. Class II MO Restoration
D. Class 1 inlay

# According to OSHA maximum permissible amount of Ni in dental clinic environment is:
A. 1 mg
B. 2 mg
C. 3 mg
D. 4 mg

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