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Fixed Prosthodontics I > Crown Preparations- Margin Design > Flashcards

Crown Preparations- Margin Design Flashcards

1
Q

Parts of a crown preparation: (4)

A
  1. axial wall
  2. interproximal wall
  3. finish line
  4. occlusal anatomy
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2
Q

A full coverage restoration can survive in the biologic environment of the oral cavity only if:

A

the margins are closely adapted to the surface finish line of the preparation

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3
Q

The design of the preparation ___ dictates the shape an bulk of restorative material in the marginal area of the restoration

A

finish line

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4
Q

Types of finish line designs include:

A
  1. knife edge
  2. chamfer (light & heavy)
  3. shoulder
  4. beveled shoulder
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5
Q

A chamfer finish line can be described as:

A

light or heavy

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6
Q

Finish line used primarily for full metal crowns only. (especially gold crowns):

A

knife edge

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7
Q

Most conservative preparation design for finish line:

A

knife edge

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8
Q

What types of burs may be used to create a knife edge finish line?

A

flame or needle-shaped diamond bur

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9
Q

The disadvantages of knife edge finish lines include:

A
  1. difficult to see the finish line in an impression or scan
  2. metal can be thin and is susceptible to distortion under heavy occlusal load
  3. often leads to an over-bulking of crown material to compensate for thinness along margin
  4. easy to miss creating distinct end of finish line and instead axial wall never terminates
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10
Q

This image shows a knife edge finish line. What is the disadvantage to B?

A

Margin is thin and susceptible to distortion

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11
Q

This image shows a knife edge finish line. What is the disadvantage to C?

A

To compensate for thin marginal area, labs all overbulk crown at margin

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12
Q

What are the indications for knife edge finish lines?

A
  1. Generally NOT indicated
  2. In certain instances like a tipped molar, a knife edge margin is possible to be conservative in an abnormal area
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13
Q

In certain instances like a tipped molar, a ____ margin is possible to be conservative in an abnormal area

A

knife edge margin

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14
Q

What is required for a knife edge margin?

A

An excellent lab technician

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15
Q

Label the following image: (left to right)

A
  1. shoulder margin
  2. chamfer margin
  3. knife edge
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16
Q

What are the two types of chamfer margins?

A
  1. heavy chamfer
  2. light chamfer
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17
Q

What type of crowns use a light chamfer?

A

metal crowns & zirconia crowns

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18
Q

What type of crowns would you use a heavy chamfer?

A
  • ceramic crowns
  • zirconia crowns
  • metal-ceramic crowns
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19
Q

What type of bur can be used to create a chamfer finish line?

A

round-end tapered diamond

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20
Q

A heavy chamfer will work for what type of crowns?

A

Any type of crown

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21
Q

When creating a chamfer axial depth more than 1/2 the bur, can create ____ of the margin which leave ___ likely to chip or break leaving an open and exposed margin

A

lipped edges, unsupported enamel

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22
Q

What are the advantages of a chamfer margin? (5)

A
  1. chamfer is well suited for full metal crowns and zirconia crowns
  2. ease of seating crown & placing of crown
  3. Ease of detecting margin on impression or scan
  4. If full metal, chamfer is easy to wax and cast
  5. provides adequate thickness of restoration material at margin area
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23
Q

A light margin chamfer is ___ deep into axial wall.

A light chamfer produces ___ degree margin with ____ internal angle

A

0.3-0.5

30-45 degrees; rounded

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24
Q

Type of margin finish line that combines a knife edge burnish-ability with bulk of material of all metal crowns:

A

light chamfer

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25
Q

Label the parts of the following crown prep:

A

A) chamfer finish line
B) functional cusp bevel
C) planar occlusal reduction
D) rounded angles
E) axial reduction

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26
Q

The chamfer finish line promotes:

A

marginal integrity

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27
Q

The functional cusp bevel promotes:

A

structural durability

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28
Q

The planar occlusal reduction promotes:

A

structural durability

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29
Q

The rounded line angles promote:

A

structural durability

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30
Q

The axial reduction promotes:

A

retention & resistance

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31
Q

A heavy chamfer provides room for:

A

thicker ceramic margin

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32
Q

The ___ of the heavy chamfer decreases material stress in the margin area.

A

internal rounded angle

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33
Q

What are the measurements of a heavy chamfer? (how deep)

A

1.0-1.2 mm deep

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34
Q

What bur is used to accomplish a heavy chamfer?

A

typically a large round-ended diamond bur

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35
Q

Label which chamfer is light and which is heavy:

A

left: light
right: heavy

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36
Q

A ___ margin design produces a close to 90 degree angle

A

shoulder

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37
Q

A shoulder margin design produces a close to ___ degree angle

A

90

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38
Q

A shoulder margin design is primarily used for ____ crowns and ____ crowns where thickness of material is important bur can also be used for ____ crowns

A

metal ceramic crowns and all ceramic crowns; zirconia

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39
Q

Modified shoulder produces a ___ angle

A

rounded

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40
Q

A shoulder margin is typically created with:

A

flat-end diamond burs

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41
Q

In a shoulder margin design, the angle of axial wall and finish line is close to 90 degrees and this functions to:

A

decrease stresses on restoration material

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42
Q

A shoulder margin design is used mostly for ____ and __ crowns

A

metal-ceramic & all ceramic

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43
Q

label the different margins shown:

A

left: shoulder margin
right: beveled shoulder

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44
Q

Some shoulder finish lines can include a bevel at a ___ degree angle

A

30-45

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45
Q

A shoulder with a bevel is often used for ___ & ___

A

inlays & onlays

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46
Q

What type of margin can be used for metal ceramic crowns where there is a metal collar?

A

beveled shoulder

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47
Q

A beveled shoulder allows for ____ of metal to ensure marginal fit

A

adaptability

48
Q

Significant roughness of preparation finish line can prevent:

A

close adaptation of crown margin

49
Q

Rough margin = ____ = ____

A

plaque accumulation; recurrent decay

50
Q

Finish line designs vary based on: (3)

A
  1. restoration material
  2. location in the mouth
  3. desired results
51
Q

The type of tooth preparation in which the finish line forms a 90-degree angle with the unprepared tooth surface:

A

shoulder

52
Q

The advantage of this type of margin includes:

  • less distortion of crown margins
  • provides adequate bulk
  • good crown contours
  • can attain good esthetics
A

shoulder

53
Q

The disadvantages of this margin includes:

  • marginal adaptation can be affected
  • more tooth structure needs to be removed
A

shoulder

54
Q

Indications of this type of margin include:

  • all ceramic crowns
  • PFM crowns
A

shoulder

55
Q

This type of margin is similar to a shoulder but has a bevel placed at the border:

A

beveled shoulder

56
Q

Indications of this type of margin include:

  • gingival finish line on the proximal box of inlays or onlays
  • occlusal shoulder of onlays and mandibular three-quarter crowns
  • the finish line for extremely short walls
  • the facial margin of posterior metal-ceramic crowns with a supragingival margin
A

beveled shoulder

57
Q

The advantages of this type of margin include:

  • to get proper marginal adaptation
  • the bulk of the material in border
A

beveled shoulder

58
Q

The disadvantages of this type of margin include:

  • more tooth structure is removed
  • less conservative approach
  • preparation should be extended apically
A

beveled shoulder

59
Q

A finish line designs for tooth preparation in which the gingival aspect meets the external axial surface at an obtuse angle:

A

chamfer

60
Q

Indications for this type of margin include:

  • cast metal restorations
  • lingual margin of metal-ceramic restorations
A

chamfer

61
Q

Advantages of this type of margin include:

  • conservative tooth prep
  • good marginal adaptation
  • provides bulk to the restoration
A

chamfer

62
Q

Disadvantages of this type of margin include:

  • technique sensitive
  • any defect in fabrication can lead to unsupported tip of the crown
A

chamfer

63
Q

Similar to chamfer finish line but comes with a 90 degrees cavosurface angle with a large radius rounded internal angle:

A

heavy chamfer

64
Q

In cases of metal restorations using a heavy chamfer margin, a ___ is added to the finish line

A

bevel

65
Q

Indications of this type of margin include:

  • ceramic crowns and metal crowns with a bevel
A

heavy chamfer

66
Q

Advantages of this type of margin include:

  • best finish line for a ceramic crown
A

heavy chamfer

67
Q

Disadvantages of this type of margin include:

  • technique sensitive
  • little discrepancy can lead to the formation of a lip or unsupported fragile enamel
A

heavy chamfer

68
Q

Also considered a thin-edge or feather-edge margin:

A

knife-edge

69
Q

Indications of this type of margin include:

  • young patients
  • metal restorations
  • MOD onlay
  • inaccessible areas
  • when the finish line extends to the cementum
  • the lingual surface of mandibular posterior teeth
  • pin ledge 3/4 quarter crown
A

knife-edge/feather-edge

70
Q

Advantages of this type of margin include:

  • Conservative
  • Helps in preserving tooth structure
  • Ideal for marginal adaptation
  • Useful in gold and metal crowns/restorations as it lets you burnish it to a fine finish
  • considered an ideal finish line
A

knife-edge/feather-edge

71
Q

Disadvantages of this type of margin include:

  • distinct or proper finish is not visible
  • polishing and casting become critical
  • overcontouring of restorations to obtain a bulk is a usual complication
A

knife-edge/feather-edge

72
Q

Crown preparation concerns:

Scientists seem to oscillate back and forth as to whether heat produced during a crown preparation will:

A

kill the pulp

73
Q

Crown preparation concerns:

It is agreed that the ___ becomes irritated and inflamed during ___.

A

pulp; crown preparation

74
Q

Crown preparation concerns:

A rise in the pulp temperature by ___ degrees significantly increases the chance of ____.

A

10 degrees; pulpal necrosis

75
Q

Crown preparation concerns:

Because of the concerns with overheating the pulp during a crown preparation we should: (7)

A
  1. use lots of water
  2. use sharp burs
  3. use light pressure
  4. use high speed
  5. use diamond burs
  6. avoid desiccation of the teeth
  7. if visibility is compromised, with an assistant, with water off from the handpiece, an assistant can use air and small amounts of water to help keep tooth cool
76
Q

The main cause of postoperative inflammation and necrosis of the pulp is probably the injury of ____, a tissue in direct functional and physiological connection with the pulp

A

dentin

77
Q

Margin design instrumentation:

For the preparation what is used? (3)

A
  1. high-speed handpiece
  2. air/water spray
  3. diamond burs
78
Q

Margin design instrumentation:

For finishing the preparation, what is used? (3)

A
  1. slow-speed handpiece
  2. fine diamond burs (possible some carbide burs)
  3. hand instruments
79
Q

Margin design instrumentation:

For caries removal of the crown preparation, what is used? (2)

A
  1. slow-speed with 2, 4, or 6 round bur
  2. spoon excavators
80
Q

Burs that function too remote enamel and dentin by grinding it away

A

diamond bur

81
Q

Burs that function to remove tooth by shearing it away:

A

carbide burs

82
Q

___ burs that are most efficient, 2-3 time faster than ___ burs

A

diamond; carbide

83
Q

What type of bur is being described?

-Cut precision prep features with smooth surfaces

  • Often used to place extra retentive features in a crown preparation such as a seating groove
A

carbide burs

84
Q

___ can be used to help smooth finish lines:

A

hand instruments

85
Q

Hand instruments that can be used to help smooth finish lines include: (4)

A
  1. chisel
  2. hatchet
  3. hoe
  4. margin trimmer
86
Q

Advantages of full metal crowns:

gold and many metal crowns are:

A

soft metals

87
Q

Full metal crowns are ____ to opposing teeth

A

gentle

88
Q

Advantages of full metal crowns:

Metal is strong so:

A

material can be quite thin

89
Q

Describe the preparations involving a full metal crown:

A

very conservative preparations

90
Q

Advantages of full metal crowns:

metals have some antibacterial properties making:

A

recurrent decay less likely

91
Q

Describe the effects of most gold and full metal crowns on the gingiva:

A

gentle

92
Q

_____ crowns are very durable even if warn through or with an endo access

A

metal crowns

93
Q

In a metal crown, if the contact is missing:

A

you can add material to the contact to re-establish it

94
Q

List the disadvantages of full metal crowns:

A

ESTHETICS

95
Q

Discuss the margin design for a full metal crown preparation:

A

Can use knife edge margin but usually a light chamfer is recommended (0.3-0.5mm)

96
Q

In a full metal crown preparation, axial walls are reduced to create a tapered wall between ___ to ___ degrees ideally, but can have TOC up to ___ degrees

A

6-10; 20

97
Q

In a full metal crown preparation, axial walls can be reduced as little as ____, but can be reduced more if needed.

A

0.5mm

98
Q

Discuss the occlusal reduction in a full metal crown preparation:

A

uniform occlusal reduction depth of 1.0-1.5 mm following tooth anatomy

99
Q

Nothing is ___ in dentistry, except for our tools

A

sharp

100
Q

In a full metal crown preparation, line angles and corners need to be rounded to prevent:

A

pressure points and possible fracturing of a restorative material

101
Q

In a full metal crown preparation, rounded preps make the:

A

crown fabrication process easier

102
Q

In a full metal crown preparation, prepared surfaces and finish line are smoothed with a fine grit diamond bur, what does this ensure?

A

preparation walls are scored but with a smoother more consistent shape for seating and longevity of the restoration

103
Q

Full metal crown summary:

A) Chamfer finish line:

B) Axial reduction:

C) Total occlusal taper:

D) Occlusal clearance:

E) ____ of all line angles

A

A) 0.3-0.5 mm
B) as little as 0.5mm
C) 6-10 dgrees
D) 1.0-1.5 mm
E) Rounding

104
Q

Label the various tooth preparations: (left to right)

A

Metal or All-Zirconia
PFM
All-Ceramic

105
Q

A relatively new material that is tooth-colored and ceramic-like:

A

zirconia

106
Q

Zirconia is considered _____ free

A

metal

107
Q

Zirconia can have similar properties to:

A

metal

108
Q

Zirconia can be described as:

A

very hard and tough

109
Q

Compare the appearance of zirconia to natural teeth:

A

less translucent

110
Q

What material is seen in the following crown?

A

zirconia

111
Q

The original zirconia that was very tough and very ugly:

A

bruxir

112
Q

Why have new iterations of zirconia been created?

A

to make zirconia more esthetic

113
Q

What is the problem with making new iterations of zirconia that is more esthetic?

A

In order to make them more esthetic, the strength of zirconia is reduced

114
Q

Depending on the type of zirconia crown, the preparation can be:

A

as minimal as a full metal crown prep or as extensive as all ceramic crown prep

115
Q

Zirconia is rapidly changing still so what is extremely important?

A

knowing which kind of zirconia your lab is using so you can prep appropriately

116
Q

The more esthetic your zirconia is, the more ____ will be needed

A

reduction

117
Q
A

Fixed Prosthodontics I (13 decks)

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