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Dentistry Module 2 > Dental Materials > Flashcards

Dental Materials Flashcards

1
Q

Q1. What is the main function of dental composites.

A

Used for Restorative (filling) materials

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2
Q

Q2. Dental composites can be used to make impressions of the dental arches, how is this carried out?

A

Dental impressions are made by placing an appropriate material in a stock or custom dental impression tray, which is designed to roughly fit over the dental arches.

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3
Q

Q3. There are two types of dental impression trays, what are they?

A

Stock tray and custom dental tray (specific to patient)

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4
Q

Q4. What does a dental resin composite consist of?

A

Resin – fibres of high strength and elasticity

Filler – harder type microparticles (quartz/silica)

Coupling Agent – resin and filler chemically to form matrix

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5
Q

Q5. A dental resin composite without a filler would most likely result in what of the composite?

A

Without a filler the resin wears easily, exhibits high shrinkage and is exothermic.

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6
Q

Q6. The coupling agent connects the resin and filler chemically to form a matrix, what are the name of the two common microparticle fillers used?

A

Quartz and Silica

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7
Q

Q7. What is needed for the formation of a matrix between the resin and filler?

A

A coupling agent

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8
Q

Q8. The GDC invites patients to ask for a statement of manufacture certificate, failure to offer statement is a criminal offence. What must be presented on the statement?

A

Patients name and confirmation made for them

Prescribers name and registered address

Technicians name and registered address

Description of the appliances

Confirmation meets legal standards

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9
Q

Q9. The end user of the product will be given a leaflet on how to use the product, it is advisable if the process chain is what and why?

A

Process chain as short and possible

Assume idiot

Time pressures

Not a slave to technology

Simple and reliable

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10
Q

Q10. The oral environment must be taken in to consideration when dealing with dental composites, what will the dental composites be subjected to?

A

Loading to 6 Kg

On/off cyclical forces – fatigue

Chemicals

Temperature fluctuations in microseconds (ice cream -14°C/Coffee 60°C)

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11
Q

Q11. What is cyclical forces referred to as?

A

Chewing

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12
Q

Q12. Why is it important for restoration to function within minutes of placement?

A

It is not acceptable for a patient to not be able to eat/drink for a long period of time, the longer the time taken for the restoration to set may cause retardation of the composite.

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13
Q

Q13. What are the 5 common materials used by the dental team?

A

Gypsum materials (plaster)

Waxes (for dentures)

Alloys (blend of metallic elements)

Polymers

Ceramics

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14
Q

Q14. Tests used to characterise materials must meet standards, why?

A

To protect the user and patient

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15
Q

Q15. Who overlooks the standard of materials used?

A

British Standards Institution (BSI)

International Standards Organisations (ISO)

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16
Q

Q16. Pulling type force test is referred to as?

A

Tensile test

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17
Q

Q17. How is strain worked out?

A

Strain = change in length/original length

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18
Q

Q18. What is the expression of the formula σ = F / A?

A

σ = Stress

F = Newtons

A = mm²

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19
Q

Q19. Why is this test not recommended for brittle materials?

A

Brittle materials do not have a flat surface on the top or bottom, and will result in cracks forming, thus not giving a true recording.

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20
Q

Q20. A diametral tensile strength test would be used for what?

A

Useful for brittle materials where conventional tensile not applicable

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21
Q

Q21. What is the expression of the formula σ = 2F/πDL

A

σ = stress

2F = 2x newtons

Π = pie 3.14

D = diameter

L = length

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22
Q

Q22. What is this test referred to as?

A

Flexural test

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23
Q

Q23. What is the expression of the formula σ = 3FL/2bd2

A

σ = stress

3F = 3x newtons

D = depth

B = breadth

L = length between rollers (support separation)

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24
Q

Q24. The box highlighted red represents what?

A

The red highlight represents the material and its stiffness, it is highlighted to show that the material will remain intact under the right stress/strain measures

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25
Q

Q25. What does the purple highlight represent?

A

The purple highlight represents the outcome when the threshold for the stress/strain measures are overcome, this results in the material losing its elasticity.

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26
Q

Q26. What does the green highlight represent?

A

The green highlight represents the failure force, this is the force where the material is failing to carry out its function.

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27
Q

Q27. What does the yellow highlight represent?

A

The yellow highlight represents the ultimate tensile stress, this is where the material completely fails.

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28
Q

Q28. What is represented by yellow highlight?

A

The yellow highlight represents resilience, the energy absorbed by the material in undergoing plastic deformation up to the elastic limit.

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29
Q

Q29. What is represented by the red highlight?

A

The red highlight represents it ductile ability - able to be drawn out into a thin wire.

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30
Q

Q30. What is represented by the blue highlight?

A

The blue highlight is a measure of toughness, this is the total amount of energy a material can absorb up to the point of fracture.

High value = tough,

low value = brittle

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31
Q

Q31. What is being represented in this graph?

A

this graph represents fatigue. Application of cyclic loading for a defined number of cycles. Material will eventually fail/survive. Greater the cyclic stress the shorter the cycle.

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32
Q

Q32. What is being represented in this image?

A

The image represents shear bond strength. This test is to test the strength of adhesive and cohesive on materials

33
Q

Q33. What is Ra – arithmetic mean deviation of the surface profile.

A

This is the measure of the surface roughness which is done by a profilometer. The higher the Ra the rougher the material.

34
Q

Q34. What is the negative of having a high Ra (surface roughness)

A

A high Ra will increase the chance of more biofilms being present > this results in the development of periodontal disease.

35
Q

Q35. Why is it important to take thermal conductivity in to account when making materials?

A

Thermal conductivity is important so that patients can sense something is hot, so they don’t swallow the substance, the more material you have in your mouth (dentures) the less you will be able to naturally feel. Thermal conductivity allows the material to transfer heat through the material at a rate before it is ingested.

36
Q

Q36. Rheological properties, is also known as?

A

The study of materials flow properties. Such as

Composite in syringes, luting cements, veneer trial pastes and impression materials.

37
Q

Q37. What affects the viscosity of a material?

A

Rate of shear (the pressure being applied)

Time (the speed at which the material is coming out)

38
Q

Q38. The graph shows three rheological properties. Which line represents viscosity increase?

A

Dilatant represents viscosity increase. The material in the syringe must require an increase in shear rate to get the material out,

39
Q

Q39. The graph shows three rheological properties. Which line represents viscosity remains?

A

Newtonian represents viscosity remains: viscosity remains with constant applied pressure.

40
Q

Q40. The graph shows three rheological properties. Which line represents viscosity decreases?

A

Pseudoplastic represents viscosity decrease. Viscosity decreases with applied pressure and, unless setting, increases when pressure decreases.

41
Q

Q41. What is one of the negatives of poor corrosion resistance?

A

Release of toxic element.

42
Q

Q42. Why should thermal expansion and contraction be taken in to account in materials?

A

Increase in heat can result in expansion of the material and its properties which can result in the material to split. It is therefore important to match the material as closely as possible to the tooth substance being replaced.

43
Q

Q43. Materials are tested before they are used in the clinical environment, how many levels of testing are there and what are they?

A

Laboratory screening – asses acute systemic toxicity, irritational properties, carcinogenic potential

Limited laboratory in vivo usage testing

Human randomised controlled clinical trial

44
Q

Q44. What are the requirements for an ideal material?

A

Non-toxic

Non-irritant

Harmless to the dental pulp

No carcinogenic potential

No irritancy

45
Q

Q45. What is gypsum

A

A soft white or grey mineral consisting of hydrated calcium sulphate. Used in dentistry to make reproductions of impressions called casts, models or dies

46
Q

Q46. What is the purpose of creating a cast?

A

Purpose of a cast is used to plan treatment and to observe treatment progress.

47
Q

Q47. What Is a die?

A

A reproduction of a prepared tooth.

48
Q

Q48. What is this CaSO4 2H2O?

A

Gypsum.

49
Q

Q49. What are three types of gypsum products?

A

Plaster

Stone

Improved stone

50
Q

Q50. What is calcination?

A

The process of heating a solid material to drive off chemically combined components such as H2O and CO2

51
Q

Q51. How do you make β dental plaster?

A

gypsum must be heated at 110/120 °c

52
Q

Q52. What are the characteristics of the dental plaster material?

A

Irregular shaped crystals

Very porous

Random shaped

53
Q

Q53. What are the two forms of plaster?

A

Type 1 gypsum = impression plaster

Type 2 gypsum = model plaster

54
Q

Q55. How do you make α dental stone?

A

Gypsum must be heated at 125°c with the presence of steam and pressure

55
Q

Q56. What are the characteristics of α dental stone/

A

More uniform shaped crystals

Denser than plaster

Larger crystals

Smoother particles

56
Q

Q57. What is type 3 gypsum?

A

Dental stone

57
Q

Q58. How do you make improved stone?

A

Gypsum along with calcium chloride (30% saturation) must be heated at 100 °c

58
Q

Q59. What are the characteristics of improved stone?

A

Very dense crystals

Cubic or rectangular crystals

Large crystals

59
Q

Q60. ADA specification – what are the 5 types of gypsum

A

Type 1 – impression plaster

Type 2 – model plaster

Type 3 – dental stone

Type 4 – dental stone high strength

Type 5 – dental stone, high strength, high expansion

60
Q

Q61. What are Gilmore needles commonly used for?

A

They are used for a surface penetration test, to measure the setting time of the gypsum material.

61
Q

Q62. The loss of surface gloss can be used as an indication for what?

A

Setting times.

Initial setting 5-7 minutes

Final set 30-45 minutes

62
Q

Q63. What is the name of a common retarder used?

A

Borax

63
Q

Q64. Will a higher water/powder ratio (creates a thinner mixture) result in a longer or shorter setting time?

A

Longer

64
Q

Q65. Name a common accelerator used for gypsum products.

A

Potassium sulphate

65
Q

Q66. Will a lower water/powder ratio (creates thicker mixture) result in a longer or shorter setting time?

A

Shorter

66
Q

Q67. What does increase mixing/decrease mixing of gypsum solution result in?

A

Increase mixing = shorter set time

Decreased mixing = longer set time

67
Q

Q68. What is hygroscopic setting expansion?

A

The expansion that occurs when gypsum sets while immersed in water

68
Q

Q69. What is normal setting expansion?

A

The expansion that occurs when gypsum sets in air.

69
Q

Q70. All gypsum products expand normally on setting, out of the 3 gypsum materials, which one expands the most?

A
  1. Plaster – 0.2% —-à 0.3%
  2. Stone – 0.08% —-à 0.10%
  3. High strength stone – 0.05% —–à 0.07%
70
Q

Q71. How does powder/water ratio affect the strength

A

High powder/water = strength

Powder/high water = decreased strength

71
Q

Q72. What occurs when the gypsum products reach dry strength?

A

The greatest surface hardness occurs

72
Q

Q73. Of the 3 materials used – which is the weakest to strongest

A

Plaster

Stone

Improved stone

73
Q

Q74. Surface detail reproduction: the impression materials viscosity must be what? to obtain less detail but can displace soft tissue.

A

High viscosity

74
Q

Q75. Surface detail reproduction: the impression materials viscosity must be what? To capture more detail but the tray won’t contain.

A

Low viscosity

75
Q

Q76. One of the requirements of impression material is for it to repel moisture on its surface, the materials ability to do this is known as?

A

Hydrophobicity

76
Q

Q77. Dimensional accuracy and stability – what type of trays may cause distortions on the impression material?

A

Flexible tray

77
Q

Q78. Give two examples of hydrocolloids used in the Dundee dental hospital

A

Alginate (irreversible)

Agar (reversible)

78
Q
A

Dentistry Module 2 (15 decks)

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