Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

SBA Dentistry > Dental Materials > Flashcards

Dental Materials Flashcards

1
Q

Which of the following would be the most appropriate autoclave regimen to adequately sterilise forceps after the removal of a mandibular molar?
a. 110C for 8 mins
b. 112C for 15 mins
c. 115C for 8 mins
d. 115C for 15 mins
e. 121C for 15 mins

A

E. 121C for 15 mins
or 134C for 3 mins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

You are designing an occlusal rest seat on the mandibular first premolar for a partial CoCr denture. Which of the following best describes the optimal depth to which the marginal ridge should be reduced?
a. 0.5mm
b. 1.5mm
c. 2.5mm
d. 3.5mm
e. 4.5mm

A

B. 1.5mm
The marginal ridge must be lowered and rounded 1-1.5mm. The bulk of the metal has to be that thickness to prevent fracture. Any greater depth than this causes unnecessary damage to the tooth.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Which of the following metals reduces the amount of creep in an amalgam restoration the most?
a. Aluminium
b. Copper
c. Iron
d. Manganese
e. Vanadium

A

B. Copper.
Creep causes protrusion of amalgam out of the cavity; the protruded edges are unsupported and weak, and may further be weakened by corrosion. This leads to fracture and microleakage. High value copper amalgam has a lower value of creep.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Which of the following is used to increase wetting in dentine bonding systems?
a. Acetone
b. Carbon tetrachloride
c. H2O
d. Methylmethacrylate
e. Phosphoric Acid

A

A. Acetone
Acetone is the best agent for the wetting f dentine. Phosphoric acid is the etchant agent and the derivates of methylmethacrylate allow a variety of strength in the bond.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What does an enamel bonding agent consist of?
a. Unfilled resin
b. Filled resin
c. A mixture of resins, acetone and ethanol
d. Wetting agents or resins
e. Prime and bond mixture

A

A. Unfilled resin.
Enamel bonding agents consist of unfilled resin.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Etched enamel does not need ‘wetting’ before enamel bonding agents are applied. Why is ‘wetting’ not required?
a. Etched enamel has a high surface free energy
b. Etched enamel has low surface free energy
c. The enamel bonding agent has low surface tension
d. The negative charge in the enamel bonding agent is attracted to the positive calcium ions in the etched enamel
e. The negative charge in the enamel bonding agent is attracted to the positive fluoride ions in the etched enamel

A

A. Etched enamel has a high surface free energy.
The high surface free energy prevents the requirement for wetting. Fluids with a low surface free energy require wetting.
Surface free energy is the energy that would be necessary to increase the surface area of a solid. It is basically surface tension but for a solid.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the bond strength achievable using enamel bonding agents on etched enamel (1MPa = 1kg/mm2)?
a. 0.1 MPa
b. 5 MPa
c. 30 MPa
d. 80 MPa
e. 250 MPa

A

C. 30 MPa
A good bond strength that is achievable with enamel bonding agents is 30 MPa.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the approximate stress caused by the polymerisation contraction of composite when it is setting?
a. 0.1 MPa
b. 5 MPa
c. 30 MPa
d. 80 MPa
e. 250 MPa

A

B. 5 MPa.
The approximate stress caused by polymerisation contraction when setting is 5 MPa.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Which one of the following is not an advantage of an enamel bonding agent over a dentine bonding agent?
a. Decreased marginal leakage
b. Better colour stability
c. Increased bond strength
d. Easier to apply
e. Decreased moisture sensitivity

A

E. Decreased moisture sensitivity.
Decreased moisture sensitivity is not an advantage of an enamel bonding agent over a dentine bonding agent. Enamel bonding agents are extremely moisture sensitive.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Which one of the following statements is correct about a dentine primer?
a. It etches dentine
b. It increases the surface free energy (wets) dentine
c. It removes the smear layer
d. It bonds to composite
e. It conditions the dentine

A

B. It increases the surface free energy (wets) the dentine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Which one of the following is true about a dentine ‘conditioner’?
a. It thinly coats collagen fibrils with resin
b. It thickly coats collagen fibrils with resin
c. It bonds to composite
d. It raises the surface free energy of dentine
e. It removes the smear layer

A

E. It removes the smear layer
The main function of the conditioner is to remove the smear layer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the usual resin in enamel bonding agents?
a. HEMA (hydroxyethyl methacrylate)
b. Bis-GMA (bisphenol A glycidyl methacrylate)
c. PENTA (phosphonated penta-acrylate ester)
d. Dismethylmethacrylate
e. Polymethylmethacrylate

A

B. Bis-GMA (bisphenol A glycidyl methacrylate).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

The solvent which is used to aid dentine wetting in dentine bonding systems is:
a. Water
b. Ethanol or acetone
c. CCl4 (carbon tetrachloride)
d. Ethylene
e. A low-molecular-weight resin

A

B. Ethanol or acetone
The solvent which is used to aid dentine wetting in dentine bonding systems is ethanol or acetone.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

The number of steps in dentine bonding is:
a. 1
b. 2
c. 3
d. 4
e. Varies

A

E. Varies
There are many different systems on the market for dentine bonding, so the number of steps is variable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the bond strength between dentine and composite when dentine bonding agents are used?
a. 1 MPa
b. 5 MPa
c. 100 MPa
d. 500 MPa
e. 1000 MPa

A

B. 5 MPa
The bond strength between dentine and composites when dentine bonding agents are used is 5 MPa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Which one of the following statements is true about the resin in a dentine bonding agent primer?
a. It is hydrophilic
b. It is hydrophobic
c. It is viscous
d. It has a high molecular weight
e. It has high surface tension

A

B. It is hydrophobic
The resins used in dentine bonding agent primers are hydrophobic

17
Q

What is the percentage of copper in a high copper dental amalgam alloy?
a. 2-12%
b. 12-32%
c. 32-52%
d. 52-70%
e. 70+%

A

B. 12-32%
The percentage of copper in a high copper dental amalgam alloy is between 12-32%

18
Q

Zinc is often used to improve the properties of amalgam. What happens to a zinc-containing low copper if moisture gets into it?
a. The alloy corrodes
b. The alloy contracts
c. The alloy is reduced
d. The alloy expands
e. None of the above

A

D. The alloy expands.
If a zinc-containing low copper alloy is invaded by moisture, it expands.

19
Q

Zinc is often used to improve the properties of amalgam. What happens to a zinc-containing high copper if moisture gets into it?
a. The alloy corrodes
b. The alloy contracts
c. The alloy is reduced
d. The alloy expands
e. None of the above

A

E. None of the above.
If a zinc-containing high copper alloy is invaded by moisture, there is hardly any change.

20
Q

Which one of these is a lathe-cut and spherical amalgam alloy mixture?
a. Hybrid
b. Admixed
c. Gamma 2
d. Non-gamma 2
e. Gamma 1

A

B. Admixed.
Admixed amalgam contains both lathe-cut and spherical-cut particles.

21
Q

Why is tin added to amalgam?
a. It decreases the reaction rate and gives adequate working time
b. It decreases corrosion
c. It scavenges water molecules
d. It increases filling strength
e. It decreases setting time

A

A. It decreases the reaction rate and gives adequate working time.

22
Q

What is the greatest disadvantage of using amalgam in posterior teeth?
a. Mercury toxicity
b. Poor aesthetics
c. Sound tooth tissue requires removal for retention
d. Increased incidence of cusp fracture
e. Decreased lifetime of restoration compared with other dental materials

A

C. Sound tooth tissues requires removal for retention.
As amalgam has no chemical bond to the tooth, it requires mechanical retention, therefore it requires further tooth removal to retain the restoration.

23
Q

How long does it take for amalgam to form a bond with the tooth?
a. 3 mins
b. 3 hours
c. 3 days
d. 3 weeks
e. 3 months

A

E. 3 Months.
Amalgam takes three months to form a bond with a tooth

24
Q

Which one of the following statements regarding the properties of casting gold alloys is correct?
a. The gold content increases on going from soft type I alloy to extra hard type IV alloy
b. The corrosion resistance increased going from a soft type I alloy to an extra hard type IV alloy
c. The strength increases going from soft type I alloy to an extra hard type type IV alloy
d. The ductility increases going from a soft type I alloy to an extra hard type IV alloy
e. None of the statements above are true

A

C. The strength increases going from soft type I alloy to an extra hard type type IV alloy.
Type I soft casting gold has 85% gold, whereas extra hard type IV alloys have only about 65%. This alters the properties of the alloy. The corrosion resistance and the ductility decrease going from a type I alloy to a type IV.

25
Q

What is the typical particle size in microfilled composite, in micrometers?
a. 0.04
b. 0.4
c. 4
d. 40
e. 400

A

A. 0.04 micrometers.

26
Q

What is different about a hybrid composite?
a. It is a mixture of composite and compomer
b. It includes a mixture of Bis-GMA and TEG-GMA (triethylene glycol-glycidyl methacrylate)
c. The filler particles are a combination of silicon dioxide and glass
d. It is a mixture of composite and glass ionomer
e. It contains both large and smaller filler particles

A

E. It contains both large and small filler particles.
Answer D defines a compomer. Almost all composites have silicon dioxide and glass filler particles, not just hybrid composites.

27
Q

What is the important property of a posterior composite?
a. It requires a single cure
b. It is dual cured
c. It is very heavily filled
d. It is very lightly filled
e. It flows easily during placement

A

C. It is very heavily filled.
Single or dual cure is not an important property of a posterior composite. The important property is that the composite is heavily filled so that it can withstand heavy occlusal forces placed on it. Lightly filled composites are more commonly used in the anterior region.

28
Q

Which one of the following materials should not be used with composites?
a. Kalzinol
b. Zinc phosphate
c. Vitrebond
d. Fuji glass ionomer
e. Poly-F

A

A. Kalzinol
Kalzinol prevents bonding of composite to enamel and dentine in a cavity

29
Q

What is the maximum thickness of a composite which can be cured by a curing light?
a. 0.5mm
b. 1mm
c. 2mm
d. 4mm
e. 6mm

A

C. 2mm
The maximum thickness that can be cured is 2mm. Any thicker than this and your composite will have a ‘soggy bottom’, and will not be stable as a restoration.

30
Q

Which one of the following events does not occur as a result of microleakage at the composite margin?
a. Secondary caries
b. Loss of the restoration
c. Sensitivity
d. Enamel fracture
e. Staining

A

D. Enamel fracture.
The restoration can debond and be lost as a result of microleakage. Also air and fluid leakage can lead to sensitivity and staining can occur especially if coloured foods leak around the margins.

31
Q

Which one of the following is not released from glass ionomer when it sets?
a. Zinc
b. Aluminium
c. Fluoride
d. Calcium
e. Sodium

A

A. Zinc
Zinc is not released from glass ionomer when it sets. All the others are released during the setting process.

32
Q

When fluoride ions leach out of glass ionomer, what replaces them?
a. Aluminium ions
b. Hydroxyl ions
c. Sodium ions
d. Carbonate ions
e. Silicate ions

A

B. Hydroxyl ions
Hydroxyl ions replace the fluoride ions which leach out of GI during the setting process

33
Q

Which one of the following statements about the curing of composites is true?
a. Exposure time of 2-3 seconds is needed for polymerisation with visible light
b. Before light activation, the base and catalyst are mixed
c. Lights of both blue and red wavelength are equally effective in polymerisation
d. Light from an argon laser will activate polymerisation
e. Light from a lithium laser will activate polymerisation

A

D. Light from an argon laser will activate polymerisation.
Light from an argon laser for usually between 20-40 seconds will cure composite

34
Q

Which one of the following composite fillers is radiopaque?
a. Quartz
b. Lithium aluminium silicate
c. Colloid silicate
d. Barium glass
E. Carbon fibre

A

D. Barium Glass
Barium is a radiopaque material and is used frequently in radiographic investigation (most commonly in barium enemas).

35
Q

What is the approximate percentage ratio of glass ionomer to resin in hybrid ionomers?
a. 80:20
b. 60:40
c. 50:50
d. 40:60
e. 20:80

A

A. 80% glass ionomer and 20% resin ionomer

36
Q

Which one of the following properties is higher for micro-hybrid composites than for micro-filled composites?
a. Modulus of elasticity
b. Water absorption
c. Thermal expansion
d. Creep
e. Polymeric shrinkage

A

A. Modulus of elasticity
An elastic modulus, or modulus of elasticity, is the mathematical description of an object or substance’s tendency to deform elastically (ie non-permanently) when a force is applied to it.

37
Q

Regarding adhesion of composite restorations to tooth structure, which one of the following statements is true?
a. Bonding forms a hybrid layer with enamel
b. Bonding to enamel is achieved by the application of an acid etchant followed by the application of a bonding agent and then composite resin
c. The bonding agent forms a micro-mechanical bond with the enamel but a chemical bond with the dentine
d. Most dentine-bonding agents bond better to a dry surface
e. Bonding occurs better without rubber dam

A

B. Bonding to enamel is achieved by the application of an acid etchant followed by the application of a bonding agent and then composite resin

38
Q

Which one one of the following statements applies to packable composites (bulk fill)?
a. Their depth of cure allows bulk polymerisation, which has been shown to be clinically effective
b. Their wear rate is dissimilar to that of amalgam
c. They are radiolucent
d. They have similar or slightly less polymerisation shrinkage than all-purpose composites
e. They exhibit more wear than compomers

A

A. Their depth of cure allows bulk polymerisation, which has been shown to be clinically effective

39
Q
A

SBA Dentistry (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions