Dental Materials MCQs - Impression Materials

# The zinc oxide eugenol impression pastes harden by :
A. Chemical reaction
B. Cold
C. Heat
D. Pressure

# Fourth state of matter is:
A. Solid
B. Liquid
C. Gas
D. Colloid

# All of the following statements about type II silicon impression material are true except :
A. They evolve hydrogen when cast if they are not fully cured
B. They exhibit a very low setting shrinkage
C. They have a lower tear resistance than polysulphide rubbers
D. They set by condensation polymerisation

# All of the following statements about an alginate impression are true except :
A. It should be rapidly displaced from the mouth
B. It may exhibit fluid exudates on the surface as a result of imbibition of water
C. It will take up water and expand if kept wet
D. It will shrink as a result of syneresis

# All of the following can be used to slow down the setting of zinc oxide eugenol impression paste except :
A. adding a small amount of glycerine
B. Adding a small amount of water
C. Altering the amount of the two pastes used
D. Cooling mixing slab

# Type I and Type II zinc oxide impression paste differ with respect to :
A. their use
B. their hardness after setting
C. water content
D. eugenol content

# Hysteresis in a hydrocolloid gel is :
A. Moisture absorption
B. Temperature lag between gelation and liquefaction temperature
C. Phenomenon of conversion of gel into sol
D. All of the above

# The term given to the phenomenon of moisture absorption by an alginate impression is :
A. Imbibition
B. Syneresis
C. Hysteresis
D. Gelation

# The base paste of condensation silicone has a low molecular weight dimethyl siloxane with a terminal group :
A. Mercaptan group
B. Hydroxyl group
C. Silane group
D. Vinyl group

# The impression with least dimensional change upon disinfection is :
A. Addition polysiloxane
B. Agar-agar
C. Polysulphide
D. Polyether

# Best material for duplicating cast is :
A. Agar-agar
B. Alginate
C. Zinc oxide - eugenol
D. Plaster of Paris

# Palladium is added to polyvinyl siloxane to :
A. act as a scavenger
B. help as a surfactant
C. act as plasticizer
D. act as a catalyst

# Syneresis seen in a hydrocolloid gel is :
A. seen as water loss
B. water absorption
C. shrinkage
D. gelation

# Immediate pouring of impressions is most critical in :
A. Condensation polysilicon
B. Addition polysilicon
C. Polyether
D. Both A and B

# Impression techniques are used for recording :
A. Oral mucous tissues
B. Dental hard tissues
C. Oral mucous tissues and dental hard tissues
D. None of the above

# The impression material used to record the prepared areas on abutment teeth is :
A. High viscosity elastomeric impression material
B. Medium viscosity elastomeric impression material
C. Low viscosity elastomeric impression material
D. None of the above

# Vulcanisation refers to the setting of :
A. Reversible hydrocolloid
B. Mercaptan impression material
C. Zinc Phosphate cement
D. Zinc oxide eugenol

# Alginate impression material is :
A. Non elastic impression material
B. Thermoplastic impression material
C. More mucostatic than ZOE
D. Less mucostatic than ZOE

# Impression plaster is :
A. Less compressive than alginate
B. More compressive than alginate
C. As compressive as alginate
D. more compressive than hydrocolloids

# Syringe material is :
A. High viscosity elastomer
B. Medium viscosity elastomer
C. Medium and low viscosity elastomer
D. Low viscosity elastomer

# Setting time of ZOE is best controlled by :
A. Adding a drop of eugenol
B. Adding a drop of water
C. Cooling glass slab
D. Altering ratio of two pastes

# The impression for a diagnostic cast of a partial edentulous mouth should be taken in :
A. Impression wax
B. Modelling compound
C. Hydro-colloid
D. Hydro cal

# Sol-gel transformation is seen in:
A. Impression plaster
B. Hydrocolloids
C. Elastomer
D. Impression compound

# Agar impression materials differ from alginate impressions in that the former sets by :
A. Mechanical action of saliva
B. Physical change
C. Evolution
D. Chemical change

# The basic constituent of reversible hydrocolloid impression material is :
A. Agar
B. Alginic acid
C. Gelatin
D. Alginate

# Which material undergoes hysteresis ?
A. Irreversible hydrocolloid
B. Reversible hydrocolloid
C. Impression plaster
D. Metallic oxide paste

# Before pouring an elastic impression, it is washed with slurry of water and stone to:
A. Increase gel strength
B. Prevent syneresis
C. Prevent distortion
D. Wash off saliva on impression

# The setting time of irreversible hydrocolloids can be decreased by :
A. Raising the temperature of water used for mixing
B. Using excess of water for mixing
C. Lowering the temperature of water used for mixing
D. None of the above

# Which material is the most difficult to remove from the patients' mouth ?
A. Metallic oxide paste
B. Silicone impression material
C. Reversible hydrocolloid
D. Impression plaster

# Rubber base impression are poured immediately as they :
A. continue to polymerise
B. become elastic
C. show imbibition and syneresis
D. show gelation

# Heavy and light body impression materials are used with :
A. Mercaptan
B. Silicone
C. Reversible hydrocolloid
D. A and B

# The most mucostatic impression material is :
A. Thin mix of plaster of paris
B. Zinc oxide eugenol impression paste
C. Free flowing wax
D. Reversible hydrocolloids

# Impression compound has which of the following characteristic property ?
A. Low thermal conductivity
B. High flow property
C. Degradation in presence of moisture
D. Remain distortion free upto 72 hours, pouring can be safely delayed

# The best way to remove a hydrocolloid impression from a patient's mouth is :
A. Slight rocking of the impression to disengage it from the undercut
B. Wetting the periphery of the impression with moist cotton to break the peripheral seal
C. Sudden jerking of the impression to prevent tearing
D. Supporting the impression along with the tray to prevent disengaging of the tray alone

# Agar syringe material can be used with/as :
A. Agar
B. Alginate impression material
C. Both of the above
D. Primary impression

# Palatal secretions affect the setting of all the impression materials except :
A. Silicone
B. Agar-agar
C. Impression paste
D. Impression plaster

# Trisodium phosphate added to alginate contributes towards:
A. Increasing the working time of alginate impression material
B. Acts as an accelerator
C. Initiating the setting reaction
D. Provides the gel strength

# Lenolin is added in ZOE paste to :
A. Decrease flow
B. Increase flow
C. Accelerate reaction
D. Decrease irritation due to eugenol

# Tear strength for impression material is highest for:
A. Condensation silicone
B. Alginate
C. Polysulfide
D. Addition silicone

# Agar is prepared from :
A. Bullock heart
B. Chemicals
C. Sea weed
D. Chick cells

# Elastomers are:
A. Alginate
B. Agar
C. Polyethers
D. Impression compound

# Perforated impression tray are used for:
A. Alginate
B. Zinc oxide eugenol
C. Agar-agar
D. Impression compound

# The American Dental Association (ADA) specification number for non aqueous elastomeric dental impression material is :
A. 19
B. 20
C. 21
D. 26

# During setting of alginate impression materials:
A. Trisodium phosphate reacts with Sodium alginate
B. Trisodium phosphate reacts with calcium sulphate
C. Colloidal gel changes to sol
D. Material in contact with soft tissues sets last

# Which of the following impression material is elastic ?
A. Impression compound
B. Zinc oxide Eugenol (ZOE) paste
C. Wax
D. Polyvinyl siloxane

# Trisodium phosphate in alginate acts as:
A. Retarder
B. Reactor
C. Accelerator
D. Plasticizer

# K2SO4 in agar agar is for :
A. accelerating the setting stage of gypsum
B. increase strength
C. Give dimensional stability
D. None of the above

# Wash or corrective impression is done by:
A. Impression plaster
B. Impression paste
C. Alginate
D. Rubber base impression material

# Hypersensitivity reactions like contact dermatitis can be caused by :
A. Polysulphides
B. Condensation silicones
C. Addition silicones
D. Polyether

# The plasticizers used in polyether impression material is:
A. Polyether polymer
B. Colloidal silica
C. Glycol ether
D. Divinyl poly dimethyl siloxane

# Impression compound base :
A. Low thermal conductivity
B. Crystalline structure
C. Formation of cross linkage with heating
D. HIgh fusion temperature

# In reversible hydrocolloid, the property by which the transformation from sol to gel and gel to sol is function of the:
A. Concentration of fillers and plasticizer
B. Percentage composition by weight of water
C. Concentration of potassium sulphate
D. Temperature

# One of the most important advantages of truly elastic impression material would be its capacity for:
A. CLose adaptation to soft tissues
B. Withdrawl without permanent distortion
C. Reproduction of surface details
D. Compatibility with gypsum products

# Alginates are :
A. Sol
B. Gel
C. Hydrocolloid
D. Colloid

# Inelastic impression material is:
A. Impression compound
B. Alginate
C. Agar-agar
D. Polyether

# Syneresis is associated with :
A. Hydrocolloids
B. Elastomers
C. Zinc oxide eugenol
D. Plaster of Paris

# Material causing minimum tissue distortion is :
A. Polysulphide
B. Silicone
C. Impression plaster
D. Zinc oxide eugenol paste

# The advantage of ZOE impression paste :
A. Has dimensional stability
B. Does not adhere to tissues
C. is easy manipulation
D. Does not require special trays

# "Brush heap" structure is found in :
A. Zinc oxide impression material
B. Agar
C. Condensation silicone
D. Polyether

# Rinsing of the impression is important to :
A. remove excess impression material
B. remove saliva
C. hydrate the impression
D. Accelerate the setting

# Gelation temperature of agar is between :
A. 20-25 degree centigrades
B. 27-33 degree centigrades
C. 37-50 degree centigrades
D. 55-60 degree centigrades

# Which is the best material fro RPD impression ?
A. Impression plaster
B. Irreversible hydrocolloid
C. Reversible hydrocolloid
D. None of the above

# Alginate impression material is similar to agar-agar impression material in the following respect :
A. Gelation increases in both on increase in temperature
B. Mixing time is increased to reduce the setting time
C. Deformation during removal of impression occurs due to distortion of gel fibers
D. Both can be reused for fresh impressions

# Which of the following is not affected by saliva ?
A. Impression plaster
B. Impression paste
C. Silicone impression material
D. None of the above

# Hardening solutions are used with impression made of :
A. Hydrocolloid
B. Impression compound
C. Elastomer
D. Zinc oxide eugenol

# Retarder in zinc oxide eugenol is :
A. CaCl2
B. Zinc acetate
C. Alcohol
D. Glycerine

# Elastomers except polyether are :
A. Hydrophilic
B. Hydrophobic
C. Water loving impression materials
D. Potassium alginates

# The cross linking agent of polysulphide rubber base impression material is :
A. Aromatic sulfonate esters
B. Stannous octate
C. Platinum salt catalyst
D. Lead dioxide

# Which of the following impression material is rigid ?
A. Zinc oxide eugenol
B. Reversible hydrocolloid
C. Alginate
D. Polysulphide rubber

# When making a polysulphide impression for a cast crown, custom trays are usually preferred over stock trays for all of the following reasons except :
A. Custom trays facilitate uniform contraction of impression material
B. Custom trays require less impression material
C. Stock trays may be short in the flange area
D. Impressions made in the custom tray are easier to remove from the mouth

# Rapid removal of rubber impressions with a single firm motion results in :
A. Reduced dimensional stability
B. Improved adhesion of the impression to the tray
C. Minimal permanent deformation
D. Reduced contamination by saliva

# Name the accelerator used in zinc oxide eugenol paste.
A. Olive oil
B. Linseed oil
C. Zinc acetate
D. All of the above

# Impression compound is characterised by all of the following except :
A. warps at room temperature
B. is a thermoset material
C. shows increased flow when kneaded with water
D. low coefficient of thermal conductivity

# The low thermal conductivity of impression compound is overcome by:
A. Impression is placed in mouth till it gets cold and sudden removal of the impression
B. By melting in boiling water at 50 degree centigrade for one hour
C. By heating with ethanol frame and directly placing in patient's mouth
D. Heating in hot water and immediately quenching in water for 20 minutes

# Which of the following is not true about elastomeric impression ?
A. Single mix materials have higher viscosity
B. Shear thinning is related to viscosity of mono phase impression material
C. Improper mixing of material can cause permanent deformation of impression
D. Putty wash technique of impression reduces dimensional change of setting

# Linear contraction of elastomeric impression with passage of time is highest in :
A. Addition silicone
B. Polysulphide
C. Polyether
D. Condensation silicone

# The process of changing the rubber base product or liquid polymer to a rubber like material is generally known as :
A. Boiling
B. Condensation
C. Vulcanisation
D. Chain lengthening

# Which of the following is true about agar hydrocolloid impression material ?
A. Liquefies between 71-100 degree centigrade
B. Solidifies between 50-70 degree centigrade
C. facilitates fabrication of metal dyes
D. cannot register fine surface details

# Alginates are made dust free by adding :
A. Glycol
B. Glycerol
C. Glutamic acid
D. Alcohol

# Which one of the following increases the strength and reduce viscosity of agar hydrocolloid impression material ?
A. Borax
B. Water
C. Sulfates
D. Carbonates

# The role of magnesium chloride in zinc oxide eugenol impression paste is :
A. Retarder
B. Modifier
C. Plasticizer
D. Accelerator

# The water powder ratio of alginate is :
A. 100 ml of water to 60 gms of powder
B. 40 ml water to 40 gms of powder
C. 40 ml of water to 15 gms of powder
D. 15 ml water to 40 gms of powder

# To make the vinyl polysiloxane hydrophilic, the following is added :
A. Mineral oil
B. Surfactant
C. Water
D. Plasticizer

# Best impression material to be used for securing impressions after crown preparation:
A. Alginate
B. Agar
C. Elastomer
D. ZnO paste

# Dimensional stability of hydrocolloid impressions can be achieved by :
A. Using less water powder ratio
B. Storing the impression under water
C. Prolonged manipulation
D. Using humidor

# Which of the following is correct regarding chemical setting of condensation silicone:
A. Polymerization occurs with repeated elimination of small molecules
B. Polymerization occurs with elimination of single byproduct
C. By condensation of repeated molecules of monomers
D. Condensation does not occur at all

# Which of the following is correct glass transition temperature of impression compound ?
A. 43.5 degree centigrade
B. 39 degree centigrade
C. 65 degree centigrade
D. 100 degree centigrade

# Which of the following is used as surface hardener in impression material ?
A. 2% potassium sulfate
B. 0.2% potassium sulfate
C. 2% sodium sulfate
D. 4% potassium sulfate

# A technique of combining reversible and irreversible hydrocolloid that could bond to irreversible hydrocolloid is known as:
A. Injecting technique
B. Laminate technique
C. Immersion technique
D. Tempering technique

# Which of the following best describes the working time of impression material?
A. After the start of appearing elastic properties of impression material
B. The time from start of mixing till just before the start of appearing elastic properties of impression material
C. Loss of luster of impression material
D. None of the above

# Minimum flow of type I impression compound at mouth temperature is :
A. 4%
B. 6%
C. 8%
D. 10%

# Which of the following is correct arrangement of impression material regarding linear contraction in ascending order ?
A. Addition silicone < Polyether < Polysulfide < Condensation silicone
B. Addition silicone < polysulfide < Polyether < condensation silicone
C. Condensation silicone < Polyether < polysulfide < Addition silicone
D. Condensation silicone < Polysulfide < Polyether < Addition silicone

# Polysulfide material is routinely not recommended because of :
A. Unpleasant odor and taste
B. Low accuracy
C. Least permanent deformation
D. Highest curing shrinkage

# Disadvantage of polysulfide as an impression material :
A. High cost
B. materials leaching out
C. Stretching leads to distortion
D. Difficulty in cast pouring

# Hydrocolloid material shows all except :
A. Hysteresis
B. Imbibition
C. Recrystallization
D. Syneresis

# Impression material which has a high incidence of air porosity is :
A. Alginate impression material
B. Impression compound
C. Zinc oxide eugenol impression paste
D. Polyether impression material

# A laminate impression technique utilizes:
A. Syringe agar and chilled tray alginate
B. Syringe agar and tray agar
C. Syringe agar and impression compound
D. Chilled alginate and impression compound

# Putty wash technique:
A. light body and putty used at the same time
B. putty used first and light body used second
C. light body first and putty later
D. None of the above

# Dimensional stability of elastomeric impression material can be given in descending order as :
A. Polysulphide > Polyether > Condensation silicone > addition silicone
B. Polyether > condensation silicone > polysulphide > addition silicone
C. Addition silicone > polyether > polysulphide > Condensation silicone
D. Addition silicone > condensation silicone > polysulphide > polyether

# The monophase elastomeric material can be used as both tray and syringe material because it has :
A. a long setting time
B. it is economical
C. pseudo plastic properties
D. better recording of tissues

# Which of the following component acts as an accelerator in ZOE impression paste ?
A. Zinc sulphate and zinc chloride
B. Zinc chloride and eugenol
C. Zinc sulphate and eugenol
D. Glycerine

# The relative hardness of elastomers is determined using :
A. Rockwell tester
B. Barcol indenter
C. Knoop pyramid
D. Shore durometer

# By product of condensation reaction between silicone base and alkyl silicate in presence of tin octate :
A. Ethyl alcohol
B. Glycol
C. Acetate
D. Propanolol

# Rough surface of elastomeric impression results from ? ( Two answers correct )
A. Inadequete mixing
B. Air bubbles
C. Too rapid polymerization
D. Imcomplete polymerization caused by premature removal from mouth

# Which of the following impression material requires a hardener ?
A. Agar
B. Alginate
C. Elastomers
D. Impression compound

# Most rigid elastomer is :
A. Polyether
B. Polysulphide
C. Addition silicone
D. Condensation silicone

# Most mucostatic among the following is :
A. Impression compound
B. Alginate
C. ZOE paste
D. Elastomer

# Most ideally elastic among the following is :
A. Polyether
B. Addition silicone
C. Polysulphide
D. Condensation silicone

# The ranking of tear strength from the lowest to highest of all impression materials generally as follows :
A. Hydrocolloids, silicones, polyether, polysulphide
B. Silicones, hydrocolloids, polyether, polysulphide
C. Polysulphide, hydrocolloids, silicones, polyether
D. Hydrocolloids, polyether, silicones, polysulphide

# Which one of the following impression materials is elastic, sets by a chemical reaction and is catalysed by chloroplatinic acid ?
A. Condensation silicone
B. Polyether
C. Polysulphide
D. Polyvinyl siloxane

# The impression material with lowest viscosity is :
A. Plaster of paris
B. Agar agar
C. Zinc oxide eugenol
D. Elastomers

# Rough and irregular surface produced on the impression is because of :
A. Improper application of pressure during impression making
B. Air incorporated during mixing
C. Too rapid polymerization
D. Presence of moisture in impression area

# Final product in alginate is:
A. Sodium alginate
B. Potassium alginate
C. Trisodium phosphate
D. Calcium alginate

# Which of the following impression materials is easy to pour and difficult to remove the stone cast from the impressions?
A. Addition silicone
B. Condensation polysilicone
C. Polyether
D. Polysulphide

# Dustless alginate is produced by :
A. Reducing the diatomaceous earth
B. Adding heavy metal salts
C. Coating with dihydric alcohol
D. altering the matrix

# "Two in one stage" impression materials include:
A. Zinc-oxide eugenol impression paste
B. Hydrocolloid impression material
C. Elastomeric impression material
D. All of the above

# Alginate fillers are derived from ?
A. Calcium sulfate
B. sodium phosphate
C. potassium alginate
D. diatomaceous earth

# In case of addition silicones, what should be done for better cast?
A. apply ketone over tray
B. apply chloroform over tray
C. add flavoring agent to prevent bad odour
D. delay pouring of the cast

# A dentist can best control the setting time of alginate impression material without altering its properties by:
A. Using perforated tray
B. Altering water :powder ratio
C. Reducing the rate of mixing
D. Altering the temperature of the water

# The elastomer having the longest curing time is :
A. Polysulphide
B. Polyether
C. Addition silicone
D. Condensation silicone