Deck 13: Biomaterials

Question 1

Which of the following mixing methods is NOT used for dental materials?

A)Two liquids mixed through a mixing nozzle
B)Powder and liquid precapsulated and mixed in a triturator
C)Powder and liquid mixed on a mixing pad
D)Two liquids agitated together using a vibrating stirrer
E)Powder and water mixed together with a spatula in a mixing bowl

Answer 1

Two liquids agitated together using a vibrating stirrer

Question 2

Which phase of the dental amalgam is the strongest?

A)Sn-Hg
B)Ag-Cu
C)Cu-Sn
D)Ag-Hg
E)Ag-Sn

Answer 2

Ag-Sn

Question 3

What range of copper is involved in the composition of high-copper dental amalgam alloys?

A)0.1% to 0.5%
B)0.5% to 1%
C)1% to 5%
D)6% to 12%
E)12% to 30%

Answer 3

12% to 30%

Question 4

What is the Mohs' hardness value for enamel?

A)10
B)7
C)5-6
D)3-4
E)1

Question 5

What is the point at which loading begins to produce both plastic and elastic strain at the same time?

A)Fracture
B)Toughness
C)Fatigue
D)Modulus
E)Elastic limit

Question 6

What is the major advantage of high-copper dental amalgam restorations over low-copper dental amalgam restorations?

A)Better mechanical properties
B)Lower coefficient of thermal expansion
C)Greater polishability
D)Lower corrosion tendency
E)Lower thermal conductivity

Question 7

Which one of the following is BEST for pulpal insulation?

A)1 mm of calcium hydroxide liner
B)1 mm of remaining dentin thickness
C)3 mm of composite restoration
D)5 mm of dental amalgam restoration
E)Surface sealant over restoration

Question 8

Which method is recommended to minimize the escape of mercury vapor during amalgam mixing?

A)Mortar and pestle
B)Friction-fit capsule
C)Precapsulated alloy and mercury
D)Covered mixing arm on the triturator
E)None of the above

Question 9

Which one of the following is NOT associated with electrochemical corrosion events?

A)Plaque
B)Crevices
C)Stress
D)Passivation
E)Translucency

Question 10

Loading of a restoration beyond the material's elastic limit produces:

A)Only plastic deformation
B)Only elastic deformation
C)Fatigue fracture
D)Elastic and plastic deformation
E)Stress relaxation

Question 11

Which one of the following materials does NOT set by polymerization?

A)Flowable dental composite
B)Hybrid glass ionomer cement
C)Dental plaster
D)Polyvinyl siloxane impression material
E)Polysulfide impression material

Question 12

Why is the linear coefficient of thermal expansion important for restorative materials?

A)It predicts the mismatch in expansion and contraction at the interface of restorative materials
B)It predicts the loss in strength of a restorative material as the temperature increases
C)It indicates the insulating characteristics of a restorative material
D)It indicates the resistance to thermal degradation of a material
E)It indicates the amount of expansion and contraction on polymerization

Question 13

Which one of the following terms is NOT important for color matching?

A)Hue, Chroma, Value
B)Ambient lighting conditions
C)Surface gloss
D)Translucency
E)Imbibition

Question 14

Which one of the following is a rapid thermal conductor?

A)Dental enamel
B)Dentin
C)Dental amalgam
D)Dental composite
E)Zirconia all-ceramic inlays

Question 15

Engineering strain is computed as:

A)Change between the initial and final strain divided by the time
B)Area under the stress-strain curve
C)Load at yield divided by elastic deformation
D)Applied load divided by the total elastic deformation
E)Deformation divided by the original length of the object

Question 16

Engineering stress is computed as:

A)Applied load divided by original cross-sectional area of the object
B)Deformation divided by the volume of the object
C)Modulus multiplied by the plastic deformation
D)Difference between the total strain and plastic strain
E)Deformation divided by the original length

Question 17

What is mixing time?

A)Time elapsed from the start of mixing until the end of mixing
B)Time elapsed from the beginning of mixing until the beginning of setting
C)Time elapsed from the beginning of the working interval until the end of the setting interval
D)The working interval
E)The time required by the operator to handle and place a dental material

Question 18

What is another name for a material's modulus?

A)Stiffness
B)Elastic limit
C)Toughness
D)Fatigue resistance
E)Brittleness

Question 19

Which phase in dental amalgam restorations is MOST likely to corrode?

A)Ag-Hg
B)Ag-Sn
C)Ag-Sn-Cu
D)Sn-Hg
E)Cu-Sn

Question 20

Which of the following materials undergoes problematic imbibition?

A)Gold restorations
B)Dental sealant
C)Dental composite
D)Dental cement
E)Alginate impression material

Question 21

What is the primary filler component composite cement?

A)Aluminum oxide
B)Polymethylmethacrylate (PMMA)
C)Silica
D)Zinc oxide
E)Calcium oxide

Question 22

Which component of the dentin bonding system is MOST likely to cause skin sensitization in dental personnel?

A)Phosphoric acid
B)Hydroxyethyl methacrylate (HEMA)
C)Ethanol
D)Urethane dimethacrylate (UDMA)
E)Bisphenol A-glycidylmethacrylate (Bis-GMA)

Question 23

What is required to produce good bond strength to dentin?

A)Long conditioning (etching) times
B)Drying of dentin
C)Preapplication of chlorhexidine
D)Postcuring materials with visible light
E)Hybrid layer formation

Question 24

Which of the following restorations requires sur?face protection with non-petroleum based jelly during APF applications?

A)Porcelain ceramics
B)Amalgams
C)Dental sealants
D)Cast gold
E)Orthodontic wire

Question 25

Which one of the following is the main criterion for failure of a high-copper dental amalgam restoration?

A)Accumulation of black or green tarnish on exposed surfaces
B)Marginal ditching along occlusal margins
C)Creep of the restoration out of the cavity preparation in proximal areas
D)Wear facets along the occlusal contact areas
E)None of the above

Question 26

What is the melting temperature of the Ag-Hg matrix phase in a set dental amalgam restoration?

A)87°C
B)107°C
C)127°C
D)147°C
E)167°C

Question 27

How do self-etching bonding systems work?

A)Acidic monomers replace need for phosphoric acid etching
B)New monomers chemically adhere to hydroxyapatite
C)Phosphoric acid is mixed with other components of the bonding system
D)Chemical bonding to collagen replaces need for micromechanical bonding
E)Wetting agent helps adaptation and replaces need for micromechanical bonding

Question 28

What is the incidence of hypersensitivity to mercury from dental amalgam restorations in the general population?

A)1 per 1000 patients
B)1 per 50,000 patients
C)1 per 1 million patients
D)1 per 5 million patients
E)1 per 100 million patients

Question 29

What is the Occupational Safety and Health Administration (OSHA) limit for exposure to mercury vapor in air during a 40-hour workweek?

A)10 µg/m3
B)20 µg/m3
C)30 µg/m3
D)40 µg/m3
E)50 µg/m3

Question 30

What is the major problem associated with polishing a dental amalgam?

A)Creation of marginal ditching
B)Burnishing of surface corrosion products into the amalgam
C)Production of a grayish color
D)Localized melting of the amalgam with mercury smearing
E)Smearing amalgam onto enamel to cause staining

Question 31

Which one of the following dental cements does NOT include polymer as part of the matrix?

A)Zinc oxide-eugenol cement
B)Polycarboxylate cement
C)Glass ionomer cement
D)Resin-modified glass ionomer cement
E)Composite cement

Question 32

What is the MOST appropriate way to manage long-term wear or discoloration of posterior dental composite restoration surfaces?

A)Replace the composite with a dental amalgam
B)Repair the worn areas with resin-modified glass ionomer
C)Resurface the old composite with new composite
D)Replace the restoration with a new high-strength ceramic
E)Adjust the occlusion of the opponent tooth

Question 33

What is the principal reason for the shift away from dental amalgam use?

A)Toxicity of mercury to office personnel
B)Environmental concerns about ineffective mercury recycling from dental offices
C)Much improved mechanical properties of other esthetic materials such as composites
D)Patient hypersensitivity problems to mercury released from amalgams
E)Lower cost of procedures for alternative restorative materials

Question 34

Which one of the following is TRUE about pit-and-fissure sealants?

A)Uncured sealant along air-exposed surfaces will finish curing in 24 hours
B)Sealants should be filled to improve their mechanical properties
C)Tinted sealants are more useful than colorless ones
D)Sealant inspection is unnecessary after 2 years
E)Partial sealing of pits and fissures is better than no sealing at all

Question 35

Where are water-miscible acrylic monomers MOST likely to be found?

A)Polishing pastes
B)APF
C)Pit-and-fissure sealants
D)Dentin primers
E)Resin surface sealers

Question 36

Which one of the following procedures does NOT require etching with phosphoric acid solution?

A)Dental sealant
B)Ceramic orthodontic bracket attachment
C)Total-etch dentin bonding procedure
D)Self-etch dentin bonding procedure
E)Amalgam bonding procedure

Question 37

Which one of the following constituents may have a palliative action on the dental pulp?

A)HEMA
B)Calcium hydroxide
C)Bis-GMA
D)4-Methacryloxyethyl trimellitate anhydride (4-META)
E)Eugenol

Question 38

What is TRUE about the dentin smear layer?

A)50- to 100-micron-thick debris layer
B)Composed mostly of collagen and water
C)Dissolved by acid etching during bonding procedures
D)Easily removed with air-water spray
E)Effectively seals dentin

Question 39

Which event does not alter the aesthetics of existing composite restorations?

A)Whitening techniques
B)Extensive tea exposure
C)Acidulated phosphate fluoride (APF) application
D)Tobacco use
E)Gum chewing

Question 40

Which restorative material is most often substituted for dental amalgam in posterior restoration applications?

A)All-ceramic
B)Dental composite
C)Hybrid glass ionomer
D)Direct gold
E)Atraumatic restorative technique (ART) material

Question 41

Why does die stone require less water for mixing than plaster?

A)Die stone powder particles pack more efficiently
B)Die stone undergoes a different reaction from that of stone
C)Die stone powder particles are less porous and imbibe less water
D)Die stone chemical reaction generates less heat and requires less cooling
E)Die stone contaminants are minimized by adding less water

Question 42

What ions on tooth structure permit glass ionomer chemical adhesion?

A)Aluminum ions
B)Calcium ions
C)Fluoride ions
D)Carboxylic acid ions
E)Hydrogen ions

Question 43

Which application typically requires the strongest gypsum material?

A)Orthodontic model
B)Master cast
C)Repairing casts
D)Removable die
E)Denture fabrication

Question 44

In high-gold casting alloys, which element produces a protective oxide on the surface of the molten alloy during the casting process?

A)Au
B)Zn
C)Ag
D)Cu
E)Pd

Question 45

What is the principal advantage of phosphate bonded investment (PBI) over gypsum bonded investment (GBI)?

A)More stability at higher temperatures
B)Stronger
C)Less setting expansion
D)Faster reacting
E)Lower cost

Question 46

How much "water of reaction" is required for the actual setting of 100 g of calcium sulfate hemihydrate powder?

A)12 mL
B)18 mL
C)24 mL
D)32 mL
E)50 mL

Question 47

What is the karatage of an alloy that is 80% gold (Au) by weight?

A)8 karat
B)12 karat
C)16 karat
D)19 karat
E)22 karat

Question 48

What is the chemical composition of gypsum powder that is to be mixed with water to form models?

A)Calcium phosphate
B)Calcium chloride
C)Calcium sulfate hemihydrate
D)Calcium carbonate
E)Calcium fluoride

Question 49

Why should molten wax application onto dies be accomplished slowly and in thin layers when creating a casting pattern?

A)Careful use minimizes porosity
B)This promotes wetting of the wax on the dies
C)This avoids distortion from thermal contraction during wax cooling
D)This has a tendency to sag because of low modulus
E)This has susceptibility to water absorption

Question 50

What pattern does the fluoride-release from glass ionomers follow?

A)Rapid decrease to a low level after 24 hours
B)Rapid decrease over 7 to 14 days
C)Decrease after 30 days
D)Increase after many months
E)No release after 1 year

Question 51

What are the primary components of an investment material?

A)Matrix, binder, and accelerators
B)Water and two powders
C)Two liquid reactants and powder
D)Matrix, filler, and modifier
E)Two pastes

Question 52

What is the major difference between plaster and stone powders?

A)Hydration state
B)Color
C)Crystal structure
D)Powder particle packing
E)Sterilization techniques

Question 53

Which one of the following materials does NOT release fluoride?

A)Traditional glass ionomer
B)Resin-modified glass ionomer
C)ART restorations
D)Provisional restorations
E)Compomer

Question 54

Which one of the following impression materials is typically mixed by extrusion through a disposable nozzle?

A)Alginate
B)ZOE
C)Polyvinyl siloxane
D)Silicone
E)None of the above

Question 55

What is the goal for the design of MOST dental inlay waxes?

A)High hardness
B)Low cost
C)Low melting temperature
D)Complete pyrolysis on heating to carbon dioxide (CO2) and (H2O)
E)Low coefficient of thermal expansion

Question 56

Which of the following choices is MOST similar to a compomer?

A)Polycarboxylate
B)Glass ionomer
C)Zinc phosphate cement
D)Composite
E)Giomer

Question 57

What is the role of paraffin in MOST dental waxes?

A)Increases tackiness
B)Increases hardness
C)Increases thermal stability
D)Acts as main low-melting component
E)Reduces thermal expansion

Question 58

Which impression material is a hydrogel?

A)Alginate
B)Zinc oxide-eugenol (ZOE)
C)Polysulfide
D)Polyether
E)Polyvinyl siloxane

Question 59

What is the chemical composition of set gypsum products?

A)Calcium sulfate trihydrate
B)Calcium sulfate dihydrate
C)Calcium sulfate monohydrate
D)Calcium sulfate unhydrated
E)Calcium sulfate hemihydrate

Question 60

Which of the following applications is MOST typical for an ART material?

A)Class III aesthetic restorations
B)Class II restorations
C)Class IV restorations in permanent teeth
D)Liner under composite restorations
E)Temporary restoration

Question 61

What are the three principal components of dental porcelains?

A)Silica, calcium oxide, and alumina
B)Alumina, zinc oxide, and calcium fluoride
C)Alumina, potassium oxide, and calcium oxide
D)Calcium oxide, magnesium oxide, and chromium oxide
E)Silica, alumina, and potassium oxide

Question 62

What does NOT harm the protective titanium dioxide surface on dental implants?

A)APF application
B)Scaling with metal instruments
C)Use of polishing agents
D)Abrasive dentifrices
E)Dental floss

Question 63

What level of chromium is required in steel alloys to produce effective passivation?

A)10-14%
B)14-18%
C)18-28%
D)28-40%
E)>40%

Question 64

What is NOT TRUE for feldspathic porcelain?

A)Excellent translucency
B)Relatively low coefficient of thermal expansion
C)Ductile
D)Used to veneer most dental porcelains
E)High hardness

Question 65

What element is responsible for producing the corrosion resistance of stainless steel instruments?

A)Cr
B)Fe
C)C
D)Co
E)Ni

Question 66

In high-gold casting alloys, which element is primarily responsible for hardness?

A)Ag
B)Cu
C)Zn
D)Au
E)Pd

Question 67

What is the general incidence of nickel sensitivity in men?

A)30%
B)25%
C)20%
D)10%
E)Lower than in women

Question 68

What events contribute to a relatively high nickel sensitivity level in women?

A)Greater contact with metal coinage
B)Contact dermatitis from nickel-based jewelry
C)Greater contact with stainless steel
D)Genetic differences
E)Less protective skin and hair during contact

Question 69

What component is involved with very-high-strength dental ceramics?

A)Silica
B)Silicon carbide
C)Potassium oxide
D)Chromium oxide
E)Zirconia

Question 70

What is the primary monomer involved in denture base fabrication?

A)HEMA
B)EMA
C)Bis-GMA
D)MMA
E)UDM

Question 71

Why are acrylic resin teeth popular for denture fabrication?

A)Light weight
B)Excellent wear resistance
C)Ease of cleaning
D)Easily bonded to denture base
E)Best esthetics

Question 72

Mouth protectors should be cleaned with:

A)Dilute chlorhexidine solutions
B)Ultrasonic agitation in baking soda solutions
C)Dilute chlorine bleach in water
D)Denture-cleaning solutions
E)Cool soap-and-water solutions

Question 73

Which one of the following terms is NOT specifically related to soldering?

A)Filler metal
B)Brazing
C)Joining
D)600 to 650 fine
E)Precious metal content

Question 74

Which application does NOT use gold alloys?

A)Cast alloy crown
B)Cast alloy bridge
C)Partial denture framework
D)Cast post and core
E)Implant

Question 75

Which is TRUE of all traditional dental cements?

A)Precapsulated
B)Endothermic reactions
C)Acid-base reactions
D)Good esthetics
E)High strength

Question 76

Which of the following dental materials CANNOT cause nickel sensitivity?

A)Dental amalgam
B)Stainless steel crowns
C)Some PFM alloys
D)Some partial denture framework alloys
E)Some orthodontic wires

Question 77

What component of dental porcelain contributes primarily to aesthetics?

A)Alumina
B)Silica
C)Potassium oxide
D)Chromium oxide
E)Titanium oxide

Question 78

Which one of the following materials practi?cally CANNOT be fabricated using CAD/CAM procedures?

A)Dental composite
B)Dental porcelain
C)Gold alloys
D)Zirconia
E)Alumina

Question 79

Which one of the following dental cement compositions requires staged additions of powder to the liquid during mixing on a chilled glass slab to control the reaction?

A)Compomer cement
B)Polycarboxylate cement
C)Resin-modified glass ionomer cement
D)Zinc phosphate cement
E)Universal cement

Question 80

What is the major problem for tissue conditioners over the first few days?

A)Increased hardness
B)Discoloration
C)Bad taste
D)Loss of bonding
E)Fungal growth