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Prostho 3 > 2. > Flashcards

2. Flashcards

1
Q

The shape of the tooth restoration provides: (3)

A

Retention
stability
mechanical strength

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2
Q

Purpose of tooth preparation? (2)

A
  • esthetics

- function

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3
Q

What do we protect during tooth prep? (4)

A
  • adjacent teeth
  • periodontum
  • pulp
  • surrounding soft tissues
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4
Q

What do we need after tooth preparation? (3)

A
  • Biological seal
  • Adequate emergence profile
  • Respect for the biological width
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5
Q

Where do we start doing the preparations on the tooth?

A

supragingivally, and only at the end take it to the desired

height

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6
Q

How do you prevent the pulp from thermal harm? (4)

A
  • water cooling
  • Sharp burs
  • Gentle and intermittent techniques
  • Use of provisionals
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7
Q

How do you protect the pulp from mechanical harm? (3)

A
  • Getting into the pulp with the bur
  • Knowledge of the anatomy
  • Diameter of the burs
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8
Q

What is the biological seal?

A

The fit between the margins of the restoration and preparation

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9
Q

What is the purpose of the biological seal? (2)

A
  • prevents cement from
    dissolving
  • prevents penetration of
    bacteria
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10
Q

What is an adequate emergence profile?

A

Restoration reproduces the tooth’s contour

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11
Q

What is the advantage of an adequate emergence profile?

A
  • Prevents dental plaque gathering preventing caries/periodontal disease
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12
Q

How do we respect the biological width with preparation margins?

A

Should be at least 2mm away from the crest bone

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13
Q

How do we respect the biological width with the finish line?

A

Should never be more than 0.5-1mm under the sulcus

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14
Q

What is the consequence of not respecting the biological width? (3)

A
  • Chronic gingival inflammation
  • Periodontal disease
  • Bone resorption
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15
Q

What components are in the biological width and their size? (3)

A

Biological width (2mm):

  • Sulcus (0.5-0.6mm)
  • Epithelial attachment (1mm)
  • Connective tissue attachment (1mm)
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16
Q

What are the 5 mechanical principles?

A
  • Retention
  • Stability
  • Path of insertion
  • Structural strength
  • Finish line
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17
Q

Define retention

A

resist the forces of dislodgment along the path of placement

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18
Q

What does NOT provide retention except in porcelain veneers?

A

Cement

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19
Q

The essential element of retention is…

A

two opposing vertical surfaces in the same preparation

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20
Q

What does a cement do?

A

Only SEALS the interface between tooth and restoration

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21
Q

What does cement provide in porcelain veneers?

A

Retention

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22
Q

What type of retention do extracoronal restorations have?

A

External retention:

  • internal surface of restoration
  • external surface of preparation
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23
Q

What type of retention do intracoronal restorations have?

A

Internal retention:

  • External surface of restoration
  • Internal surface of preparation
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24
Q

What factors influence retention?

A
  • Magnitude of dislodging forces
  • Marginal adaptation
  • Cements
  • Morphology of the prep
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25
Q

What factors minimize crown retentiveness? (4)

A
  • Short teeth
  • No marginal adaptation
  • Cementation technique
  • Sticky food
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26
Q

What dislodging forces can influence retention?

A

Magnitude of vertical forces in occlusal directions

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27
Q

How can marginal adaption influence retention? (2)

A
  • proper adaptation gives friction and retention

- impression quality and lab procedure affects marginal adaptation

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28
Q

How do cements influence retention? (3)

A
  • increase retention by increasing friction
  • micromechanical bonding
  • there is NO chemical bonding
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29
Q

Whats the relation between friction and retention?

A

Directly proportional. Increasing one increases the other

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30
Q

What are the most important factors that influence retention? (2)

A
  • Marginal adaptation

- Morphology of the preparation

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31
Q

What factors of tooth preparation influence retention? (4)

A
  • Slight conicity
  • Volume
  • Type of restoration
  • Unique path of insertion
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32
Q

How is conicity related to retention?

A

Inversely proportional

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33
Q

What is the ideal conicity situation?

A

Most retentive preparation is no conicity with parallel walls

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34
Q

What is the purpose of giving conicity to the preparation?

A
  • Allows insertion and complete sealing of restoration

- Provides aqeduqate retention/friction

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35
Q

Why should tooth preparation in conicity be kept minimal? (3)

A
  • Adverse effect on retention
  • Preserves as much tooth as possible
  • Limits the number of paths that a restoration can be removed
36
Q

How many degrees do we prepare the tooth’s conicity?

A

3 degrees on each side

37
Q

How do we prepare the tooth’s conicity? (3)

A
  • Use tapered diamond bur
  • Hold it parallel to the path of insertion
  • Converge in occlusal direction
38
Q

How does volume relate to retention? (2)

A
  • Directly proportional

- More surface = more friction= more retention

39
Q

How does height relate to retention?

A

More height = more retention

40
Q

If a tooth is short, how can we maximize height? (3)

A
  • Move the finish line apically
  • Preparing the occlusal surface as little as possible
  • Build boxes and guiding grooves
41
Q

How does diameter relate to retention? (2)

A
  • More diameter=more friction=more retention

- If a tooth is too narrow, can build boxes and guiding grooves in the proximal surfaces

42
Q

External or internal retention: PFM crown?

A

External

43
Q

External or internal retention: Inlay?

A

Internal

44
Q

Define stability (2)

A
  • to be firm/steady

- resist displacement by horizontal or rotational stresses

45
Q

What factors influence stability? (3)

A
  • Magnitude and direction of the force
  • Geometry of dental preparation
  • Physical properties of the cement
46
Q

What forces interfere with stability? (2)

A
  • Tangenital forces

- Forces due to interferences /pre maturities

47
Q

What factors of tooth preparation affect stability? (4)

A
  • Adequate conicity
  • lateral boxes and grooves
  • length : mesiodistal width
  • length : faciolingual width
48
Q

The MORE conical is the preparation, there

will be a higher probability for the restoration to …

A

Rotate

49
Q

How does conicity relate to stability?

A

More conicity = less stability

- more removal paths

50
Q

How does no conicity relate to insertion?

A

No insertion

51
Q

When do we use lateral boxes and grooves?

A

When the conicity, height of diameter is not the recommended value

52
Q

What are lateral boxes and grooves used for?

A

To reduce the freedom of displacement of the restoration

53
Q

When do we prepare a box?

A

when there is not enough height. On the M and D surfaces

54
Q

When / where do we prepare a groove? (4)

A
  • When there is a lack of height and a wide M-D distance.
  • Parallel to the insertion path.
  • One groove
  • In Buccal if lower molars, In Palatal if Upper molars
55
Q

The length of a tooth must be great enough to…

A

Interfere with the arc of displacement

56
Q

Stability: A higher preparation will prevent…

A

The rotation of the restoration

57
Q

Stability: The length of the axial wall must be high enough to … (2)

A

Counter the length of the rotational radius

- depends on mesio-distal diameter

58
Q

What kind of stability will a narrower preparation have?

A

More stability due to a shorter rotational radius

59
Q

What Length to Facio-Lingual Width Ratio is needed? (2)

A
  • 0.4

- 4mm height for 10mm wide

60
Q

What is the importance of a length:facio-lingual width ratio on stability? (2)

A
  • movements in a buccolingual sense
  • (ex: lateral movements of
    the jaw in a group function situation)
61
Q

Define path of insertion (2)

A
  • SPECIFIC DIRECTION the PROSTHESIS IS PLACED ON
    THE ABUTMENT TEETH OR IMPLANT
  • Unique imaginary line determined before starting the preparation
62
Q

What is the ideal path of insertion?

A

Parallel to the long axis of the tooth

63
Q

The path of insertion is given by…

A

the preparation of the axial walls

64
Q

The PATH OF INSERTION must be considered in two dimensions: (2)

A

FACIO-LINGUALLY

MESIO-DISTALLY

65
Q

Path of insertion: facio-lingually? (2)

A
  • Important in the anterior sector.

- path of insertion parallel to the long axis of the tooth.

66
Q

What happens if the tooth preparation is too buccally inclined? (2)

A
  • overcontoured restoration OR

- Unesthetic due to a lack of volume of the ceramics

67
Q

What happens if the tooth preparation is too palatally inclined? (2)

A
  • mechanical issues due
    to a very short preparation OR
  • biological issues for invading the pulp chamber
68
Q

How should the path of insertion be mesio-distally?

A

Parallel to the adjacent teeth so they don’t interfere with the insertion

69
Q

Abutments in bridges should all be…

A

parallel to each other

70
Q

What do we do if the abutment tooth of a bridge is inclined? (3)

A
  • Follow the inclination of the abutments that are not inclined.
  • May need endodontic treatment
  • Orthodontic treatment
71
Q

If you do not have a correct visual of the path of insertion is means..

A

There are retentive areas to correct

72
Q

Structural strength depends on…?

A

Repescting and removing the correct volumes

73
Q

What are the parameters to achieve structural strength? (3)

A
  • Occlusal reduction
  • Functional cusp bevel
  • Axial reduction
74
Q

What is important to remember with occlusal reduction in regards of structural strength? (2)

A
  • Have correct volume, respecting the anatomy of the tooth.

- Must provide enough space for the material.

75
Q

What happens when the occlusal surface is too flat?

A

Areas too close to the pulp and other areas with lack of space for the material

76
Q

What is the functional cusp bevel thickness for PFM?

A

2mm

77
Q

What is the functional cusp bevel thickness for gold?

A

1.5mm

78
Q

What happens if the restoration material is not thick enough? (2)

A
  • Perforation in the metallic crown

- fracture of ceramic in PFM crowns

79
Q

What happens if the functional cusp bevel is thick enough but there is not enough prosthetic space? (2)

A

Pre-maturities and interferences

80
Q

If you overcontour the axial surface, what will occur? (2)

A
  • strengthens the restoration

- negative effect on the periodontum

81
Q

Occlusal reduction of metallic crowns? (2)

A

Functional cusp: 1,5mm

Non-Functional cusp: 1mm

82
Q

Occlusal reduction of metal-porcelain crowns? (2)

A

Functional cusp: 2mm

Non-Functional cusp: 1,5mm

83
Q

Occlusal reduction of all ceramic crowns? (2)

A

Functional cusp: 2mm

Non-Functional cusp: 2mm

84
Q

Axial reduction of gold crowns?

A

1mm (0.5 chamfer)

85
Q

Axial reduction in anterior PFM crowns? (4)

A

Labial reduction: 1,2-1,5mm
Lingual Concavity: 1mm
Lingual Reduction: 1mm (o,5 chamfer)
Proximal 1mm

86
Q

Axial reduction in posterior PFM crowns? (3)

A

Buccal reduction: 1,2-1,5mm
Lingual reduction: 1-1,5mm (0,5 chamfer if metallic finishing)
Proximal: 1-1,5mm (0,5 chamfer)

87
Q

Axial reduction in all ceramic crowns? (3)

A

Buccal reduction: 1,2-1,4mm (1mm shoulder)
Lingual: 1mm
Proximal 1,2-1,4mm

Prostho 3 (11 decks)

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