Dr.
Mohamed tharwat
Chapter 3 (investment mPaterials)
Multiple Choice Questions
1- Silica in any dental investment material results in
a- Increasing porosity b- heat resistant
b- Expansion on setting c- reconstructive transformation
2- Metallic casting ring with wet liner is used with
a- Silicate bonded investment b – universal type investment
b- Phosphate bonded d –gypsum bonded
3- Investment material should be porous to:
a- Allow hygroscopic expansion c- allow thermal expansion
b- Escaping of air from mold space d. B&C
4- The purpose of heating the investment are to
a- Increase the hygroscopic expansion of investment
b- Expand the mold thermally
c- Eliminate wax pattern from the mold
d- B&C
5- Artificial venting is essential in
a- Gypsum bonded investment c- phosphate bonded investment
b- Silicate bonded investment d. all of the above
6- Too small casting may be due to
a- Insufficient heating of the investment material
b- Insufficient melting the alloy
c- Improper selection of the investment material
d- a&c
7- The casting shrinkage of gold alloy is approximately
a- 1.6 % b. 0.5% c. 2.3% d.3%
8- Air bubbles can be reduced in investment by
a- Investing under water b- mixing the investment under vacuum
b- Using high water/powder ratio d- using low water powder ratio
9- Investment material must be
a- Strong b- porous c- heat resistance d. all of the above
10- The expansion of investment that occurred when immersed in water is
a- Setting b- hygroscopic c- imbibition d- humidification
Dr.Mohamed tharwat
11- Investment material should be
a- Strong b- non porous c- heat resistant d – a &c e- all of the above
12- Silica is present in investment material to provide
a- Mold contraction on heating b- mold expansion by heating
c. Mold expansion by hygroscopic expansion
13- Gypsum bonded investment
a- It is used for casting gold alloys
b- Not suitable for higher fusing dental alloys
c- Sulfur trioxide gas evolved if it is heated at 1200C
d- All of the above
14- The role of refractory material in investment material is
a- To produce porosity in the investment
b- To decrease the expansion of the investment
c- To decrease the strength of the investment
d- Non of the above
15- The investments used for casting of gold alloys are:
a- Gypsum bonded investment
b- silicate bonded investment
c- Phosphate bonded investment mixed with silica sol
d- phosphate bonded investment mixed with water
e- A&D f- B&C
16- The investments used for casting of base metal alloys are:
a- Gypsum bonded investment
b- silicate bonded investment
c- Phosphate bonded investment mixed with silica sol
d- phosphate bonded investment mixed with water
e- A&D f- B&C
17- The casting shrinkage of base metal alloy is approximately
a- 1.6% b- 2- 2.3% c- 0.5 % d- 3%
18- During casting procedure, sprue acts as a reservoir for the molten alloy to:
a- Prevent fracture of the investment c- prevent shrinkage of investment
b- Compensate for solidification shrinkage of the alloy
f- Allow escape of air
19- The main constituents of the investment material is the
a- Modifier b- retarder c- refractory material d. accelerator e. binder
20- The pathway for the molten casting metal to reach the mold formed in the
investment is known as
a- Ceramic liner b- crucible c. casting ring d. sprue
Dr.Mohamed tharwat
21- Which of the following materials need rubber ring
a- Gypsum bonded b- phosphate bonded with water c- silicate bonded d- all of the above
22- Which of the following investment materials have setting contraction
a- Phosphate bonded b- silicate bonded c- gypsum bonded d. all of the above
true and false:
1- The binder is the main composition of the investment material F
2- The investment material should have porosity to withstand force of entering metal F
into the mold
3- Silicate bonded investment is suitable for casting of noble alloys while gypsum
bonded investment is suitable for base metal alloys F
4- High thermal expansion of the investment material because the prescence of large
amount of copper F
5- Beta cristobalite can be transformed to beta tridymide F
6- Reconstructive transformation of silica is accompanied by thermal expansion F
7- Cristobalite used for casting, while quartz used for soldering F
Chapter 4 (casting technology)
Multiple choice questions
1- Too small casting may be due to
a- Insufficient heating of the investment material
b- Insuffiecient melting of the alloy
c- Improper selection of the investment material
d- A&C
2- Too large castin may be due to:
1- Incomplete wax elimination
2- Improper selection of investment material
3- Insufficient melting of alloy
4- Insufficient heatin of investment material
3- The most difficult alloy to cast
a- Gold alloy b- cobalt chromium alloy c- nickel chromium alloy d- titanium
4- Incomplete casting may be due to
a- Insufficient force b- incomplete melting c- incomplete wax elimination
b- All of the above
5- The use of too narrow sprue diameter during casting will result in
a- Back pressure porosity b. localized shrinkage porosity
b- Necking d. all of the above
Dr.Mohamed tharwat
6- During casting the length of the sprue should be adjusted to keep the wax pattern
at………….. from the end of the casting ring
a- More than 8 mm b- less than 6mm c- 6-8mm d. all of the above
7- Improper use of wetting agent during investing of wax pattern leads to
a- Surface discoloration
b- Surface roughness and irregularities of casting
c- Oversized casting
8- Distorted casting may be due to
a- Proper selection of investment material b- immediate investing of wax pattern
b- Over heating of investment d. improper handling of wax pattern
9- Shrinkage spot porosity may occur during casting as a result of
a- Incorrect attachment of the sprue b- improper feeding of the mold with molten
metal
b- Using of thin sprue d. all of the above
10- During casting metallic ring should be lined with ring liner to
a- Allow space for expansion b- facilitate removal of investment
b- Allow hyhgroscopic expansion d. all of the above
11- Incomplete casting with rounded edge may be due to
a- The use of thin short sprue b. sufficient casting pressure
b- The use of long sprue d. sufficient venting of the investment
12- More centrifugal casting force is required for:
a- Gold alloy b- cobalt chromium c- nickel chromium d- titanium
d- B&C&D
13- An undersized cast crown result from
a- Using thin sprue b- using thick sprue
b- Improer selection of investment d. using a rubber casting ring
14- To increase hygroscopic expansion of gypsum bonded investment
a- Use rubber ring with liner b- use metallic ring with liner
b- Use rubber ring d. use metallic ring with wet liner
15- During casting of metal te sprue should be made of
a- Wax b- plastic c- metal d. ceramic
Dr.Mohamed tharwat
True and false:
1- Porosity in dental casting related to sprue length T
2- High thermal expansion of silicate bonded investment is due to prescence of large
amount of silica T
3- If gypsum bonded investment is heated at high temperature it could be used for
casting base metal alloy F
4- Using wetting agent before investing wax pattern decrease surface roughness T
5- The diameter of the sprue should be thicker than thickest part of wax pattern T
6- The sprue should be attached at 45 to the proximal wall of the wax pattern T
7- The use of wet liner can allow thermal expansion of the investment F
8- The use of the regular mix technique for investing the wax pattern is recommended F
9- Metallic sprue should be removed after wax elimination F
10- Wax pattern should be delayed invested to avoid distortion F
11- The use of wetting agent (surfactant) will increase surface roughness of the final
restoration F
12- Base metal alloys can by finished and polished by pickling F
13- An over sized casting is obtained due to improper handling of wax pattern F
14- Hand investing procedure is highly recommended to obtain casting with minimal surface
defects F
15- Shrinkage porosity in casting is related to sprue length F
16- A rounded margin in a casting can be due to insufficient casting pressure T
17- Melting gold alloys is done by an oxyacetylene flame while, melting base metal alloy is
done by the blue zone of the blow pipe flame F
18- Rubber ring is used in casting of gold alloys while metal ring is used in casting of base
metal alloy F
19- Improper handling of wax pattern leads to incomplete casting F
Chapter 5 (dental casting alloys)
Multiple choice questions
1- Which one of the following is responsible for lowering the melting temperature of
base metal alloy be 100c
a- Copper b- chromium d- cobalt c- beryllium
2- Carbon content in base metal alloys:
a- Increase the strength b- increase melting temperature d- act as grain refiner
3- Which of the following is used in polishing of base metal alloys
a- Pickling b- electro-polishing c- electroplating d- rubber cups
4- Commonly occurring at the edges of the flange of denture
a- Granular porosity b- contraction porosity c- gaseous porosity
Dr.Mohamed tharwat
5- Titanium is considerd a material of choice of implant because
a- It has high thermal conductivity
b- It forms passive layer
c- It has low density
6- Aluminum is added to base metal alloys containing nickel in oreder to increase
a- Ductility b- strength c –flexibility d – fluidity
7- Cobalt chromium alloys ideally used for construction of denture framework, this is
due to
a- The density is double than that of gold alloys
b- The high modulus of elasticity of cobalt chromium alloys
c- The low modulus of elasticity of cobalt chromium alloys
d- The high flexibility of cobalt chromium alloys
8- Casting of titanium is highly technique sensitive due to
a- High melting temperature
b- Very low density
c- High chemical reactivity with oxygen
d- All of the above
9- Base metal dental casting alloys:
a- Have good tarnish and corrosion resistance due to high nobility
b- Are easy to cast
c- Are easy to finish and polish
d- Are light in weight
10- The primary deoxidizer in base metal alloys:
a- Cobalt
b- Nickel
c- Molybdenum
d- Zinc
11- Dental casting alloys are those used for construction of:
a- Crown and bridge
b- Impression
c- Direct metallic restoration
d- All of the above
12- Base metal alloys can be used in thin section due to their high
a- Ultimate strength b –hardness c- modulus of elasticity d- yield strength
Dr.Mohamed tharwat
13- Compared with type IV gold alloys , cobalt chromium is
a- about half as dense
b- has higher casting shrinkage
c- are easier in finishing and poishing
d- use the same type of melting and casting equiepment
e- a&b
14- Melting of base metal alloys is done using
a- air gas blow bibe torch b- oxyacetelyne flame
b- sand blasting machine d- non of the above
15- Nickel in base metal alloys is responsible for the…………… of the alloy:
a- britlleness b. carcinogenic property c. ductility d. resilience
16- The alloy used for the ceramo-metallic restoration must be
a- silver and copper in high percentage amount
b- high sag resistance
c- low modulus of elasticity
d- low ductitlity
17- Base metal alloys can be used in thin sections due to their high
a- modulus of elasticity b- hardness c- yield strength d- ultimate strength
18- ……………… act as grain refiner in base metal alloys
a- Iridium b- molybdenum c- manganese d. beryllium
19- Dental casting alloys should have high modulus of elasticity to
a- To resist elastic deformation b- to be used in thin sections
b- To allow equal stress distribution d. all of the bove
20- Dental casting alloys should have high resilience
a- To absorb energy without permenant deformation
b- To be used in tin sections
c- To allow equal distribution of force
d- To resist cycling loading
21- The increased carbon percentage in base metal alloys leads to
a- Increase the melting temperature b- increase the brittleness of the alloy
b- Increase tarnish and corrosion d. increase strength
22- ……………… increase strength and rigidty of base metal alloy
a- Cobalt b. chromium c. copper d. beryllium
Dr.Mohamed tharwat
23- High ductility is required in dentall casting alloy as it allows
a- Ease of burnishability b- ease of casting d. compatible with porcelain
b- Ease of soldering
24- More casting pressure is needed for
a- Gold alloys b- cobalt chromium aalloy c- nickel chromium alloy
b- Titanium d. all of the above
25- Silicon and manganes added to base metal alloys to
a- Improve te castability
b- Increase the strength
c- Decrease melting temperature
d- All of the above
26- Compared with type IV gold alloys, cobalt chromim alloys
a- Are about half as dense
b- Use the same type of melting and casting equipment
c- Are easier to finish and polish
27- Chromium in base metal alloys is responsible for
a- The increase in elastic modulus b- the brittleness of the alloy
b- Resistance to tarnish and corrosion by formation of passive layer
c- The ductility of the alloy
28- Corrosion resistance of some base metals known as
a- Nobility b- sensitization c- resistivity d- passivity
True and false
1- Commercially pure titanium can be used in sever cut because it is a flexible
metal T
2- Mechanical properties of commercially pure titanuim are like that of type III
and IV gold alloys F
3- Titanium is highly resisting tarnish and corrosion because it is a noble metal F
4- Noble alloys have good tarnish and corrosion resistance due to passive layer F
5- Nickel chromium alloys have lower percent of elongation than cobalt chromium F
6- Casting of titanium is very difficult T
7- The higher density of base metal alloys requires lower more centrifugal force during
casting than F
8- Recasting of base metal alloys is not recommended T
9- Beryllium increase the fusion temperature of the base metal alloys F
10- Nickel is responsible for strength and hardness of base metal alloys F
11- Nickel chromium are commonly used in R.P.D framework F
Dr.Mohamed tharwat
12- In long span bridge base metal alloys can be used in thick sections than gold alloys F
13- Base metal alloys have higher density than gold alloys F
14- Base metal alloys are flexible than gold alloys F
15- Base metal alloys alloys are resistant to tarnish and corrosion due to prescence of
passive layer T
Chapter 6 (non- metallic denture base)
Multiple choice questions
1- Mixing the polymer and monomer of acrylic rein in open glass container leads to
formation of
a- Gaseous porosity
b- Granular porosity
c- Internal porosity
2- Crazing of heat cure acrylic resin denture material may occur due to
a- Prescence of fillers
b- Repeated wetting and drying
c- Prescence of residual monomer
3- Polymer/ monomer ratio in acrylic resin by volume should be:
a- 2.5 -1
b- 1- 3
c- 3-1
d- 1-1
4- Polymer/ monomer ratio in acrylic resin by weight should be:
a- 2.5 -1
b- 1- 3
c- 3-1
d- 1-1
5- ………… added to acrylic resin in order to increase shelf life:
a- Hydroquinone
b- Cross linking agent
c- Impression
d- Nylon fiber
e- Plasticizer
6- Self cure acrylic resin can be used for construction of:
a- Full crown b- special tray c- partial denture d- complete denture
7- Heat cure acrylic resin denture base characterized by:
a- Low thermal conductivity and high coefficient of thermal expansion
b- Low thermal conductivity and low coefficient of thermal expansion
c- High thermal conductivity and low coefficient of thermal expansion
Dr.Mohamed tharwat
8- The main component of flexible denture is:
a- Poly sulfide
b- Polymethylmethaacrylate
c- Methylmetha crylate
d- Poly amide
9- Addition of butadiene styrene rubber inclusion to acrylic resin denture bas leads to
increase
a- Compressive strength
b- Tensile strength
c- Transverse strength
d- Impact strength
10- The acrylic resin should be packed in the mold cavity at stage of
a- Sandy b- sticky d- dough
11- The desirable stage of packing of acrylic resin into the flask is:
a- Sandy stage b- sticky stage c- dough stage d- rubbery stage e- stiff stage
12- The porosity that may caused by monomer boiling, during processing a denture
base is localized in:
a- The thin palatal c- the surface of thick ridge portion
b- The interior of the thick ridge portion d- both A&B
13- Acrylic resin denture base with porcelain teeth may lead to:
a- Contraction porosity c- gaseous porosity
b- Crazing d- dimensional changes
14- Benzoil peroxide component of acrylic resin is
a- Activator b- initiator c- plasticizer d- cross linking
15- Butyl phthalate component of acrylic resin is
a- Activator b- initiator c- plasticizer d- cross linking
16- The activator in chemical cured acrylic resin is
a- Benzoil peroxide b. tertiary amine c. butyl phthalate d. vinyl chloride
17- Using a high liquid/powder ratio during mixing acrylic resin leads to:
a- Shrinkage porosity b- granular mix c- gaseous porosity d. all of the above
18- Packing of acrylic denture base in rubbery stage
a- Is desirable b- may result in porosity in the final denture
b- The material will be too viscous to flow under the pressure of the flask pores
c- A&C
19- The first stage of addition polymerization
a- Initiation b- activation c- propagation d. termination
Dr.Mohamed tharwat
20- Factors controlling the formation of dough stage are
a- Molecular weight b- particles size c- all of the above
21- Long cycle is preffered to short cycle due to
a- Reduce shrinkage porosity b- obtain high degree of polymerization
b- Increase water sorption c- obtain an oversized denture
22- Aluminum and fibers added to PMMA
a- to increase modulus of elasticity
b- decrease coefficient of thermal expansion
c- to decrease TG
d- a&b
23- A broken denture is fixed by
a- Resilient liner b- heat cured acrylic resin c- self cured acrylic resin
b- Tissue conditioner
24- After processing in dry condition , non metallic denture base resin:
a- Undergoes expansion b- undergoes shrinkage c- liberates water
b-
25- An ideal non metallic denture base must
a- Have high density b- have low impact strength c- have low modulus of elasticity
b- Be easy to repair
26- The monomer should kept in tightly sealed dark bottle to avoid:
a- Evaportoin b. discoloration c. self polymerization d. non of the above
27- Residual monomer in acrylic resin denture base results from
a- Processing at too low temp b. processing at too low time
b- Processing at too high temperature d. both a&b
28- Benzoil peroxide is used in the powder component of the mixture for processing
PMMA to:
a. Increase shelf life of the powder b. retard the rate of polymerization
c. Increase solubility of the powder d. initiate the polymerization reaction
29- Internal porosity is most likely to occur in which portion of the denture:
a. On the surface b. in surface located near the flask c. in the center of the thick
portion
30- Using high monomer/powder ratio in the mixture for proccessing PMMA will result
in
a- Polymerization expansion b. no effect on shrinkage c. high polymerization
shrinkage
Dr.Mohamed tharwat
31- The inhibitor used in the liquid component of the mixture for processing PMMA is
a- Butyl phthalate b- vinyl chloride c. hydroquinone
32- Polymerization of cold cure PMMA is achieved by:
a- Heating b- light c- chemical activation
33- Heat cured acrylic resin is preferred to chemical cure in making denture base to:
a- Chemical cure has higher amount of uncured residual monomer
b- Chemical cure has high color stability
c- Chemical cure has higher glass transition temperature
d- Chemical cured has less susceptibility to crazing
Traue and false
1- The denture base should have low thermal connducivty to avoid burning sensation F
2- The main component of flexible denture base is polyamid T
3- Powder/ liquid ratio during mixing of acrylic resin sould be 3:1 by weight F
4- During heat curing of denture base short cycle used for small denture while long cycle
used for large denture T
5- Plasticizers increase the glass transition temperature of polymers F
6- Crazing in denture base increases by using cross-linking agent F
7- Cross linking agent decrease strength, hardness, TG and increase water sorption and
crazing F
8- Hydroquinone is used as inhibitor to prevent polymerization during storage T
9- Chemical cured acrylic resin used to construct denture base while heat cured used to
construct special tray F
10- Denture base should have high modulus of elasticity and low transverse strength F
