Crown Preparations- margin design Flashcards
(118 cards)
1
Q
Parts of a crown preparation:
A
- axial wall
- interproximal wall
- finish line
- occlusal anatomy
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
3
Q
The design of the preparation ______ dictates the shape and bulk of restorative material in the marginal area of the restoration
A
finish line
4
Q
Types of finish line design include:
A
- knife edge
- chamfer (light and heavy)
- shoulder
- beveled should
5
Q
A chamfer finish line can be described as:
A
light or heavy
6
Q
Finish line design that is used primarily for full metal crowns only. (Especially gold crowns):
A
Knife edge
7
Q
Most conservative preparation design for the finish line :
A
Knife edge
8
Q
What may be used to create a knife edge finish line?
A
Flame or needle-shaped diamond bur
9
Q
The disadvantages of knife edge finish lines include:
A
- difficult to see finish line in an impression or scan
- metal can be thin & susceptible to distortion under heavy occlusal load
- often leads to an over-bulking of crown material to compensate for thinness along margin
- easy to miss creating distinct end of finish line and instead acial wall never terminates
10
Q
This image shows a knife edge finish line. What is the disadvantage to B?
A
Margin thin and susceptible to distortion
11
Q
This image shows a knife edge finish line. What is the disadvantage to C?
A
To compensate for thin marginal area, labs will overbulk crown at margin
12
Q
What are the indications for the use of knife edge margin finish lines?
A
- generally NOT indicated
- in certain instances like a tipped molar, a knife edge margin is possible to be conservative in an abnormal area
- must have an excellent lab technician
13
Q
In certain instances, like a tipped molar, a _____ margin is possible to be conservative in an abnormal area
A
knife edge
14
Q
Label the following types of margin finish lines:
A
(left to right)
1. shoulder
2. chamfer
3. knife edge
15
Q
What is required for a knife edge finish line?
A
An excellent lab technician
16
Q
What are the two types of chamfer margins?
A
- heavy chamfer
- light chamfer
17
Q
What types of crowns use a light chamfer?
A
Metal crowns & zirconia crowns
18
Q
What types of crowns use a heavy chamfer?
A
-Ceramic crowns
-Zirconia crowns
-Metal-ceramic crowns
19
Q
What type of bur can be used to create a chamfer finish line?
A
Round-end tapered diamond
20
Q
A heavy chamfer will work for what type of crowns?
A
Any type of crown
21
Q
When creating a chamfer margin finish line 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
22
Q
What are the advantages of a chamfer margin finish line? (5)
A
- chamfer is well suited to full metal crowns & zirconia crowns
- ease of seating & placing crown
- ease of detecting margin on impression/scan
- if full metal, chamfer is easy to wax & cast
- provides adequate thickness of restoration material at margin area
23
Q
A light chamfer is ______ deep in axial wall
A light chamfer produces a _____ degree margin with rounded internal angle
A
0.3-0.5 mm
30-45 degree margin
24
Q
A light chamfer produces a a ____ internal angle
A
Rounded
25
Type of margin finish line that combines knife edge burnish-ability with bulk of material for all metal crowns:
Chamfer
26
Label the parts of the following crown prep:
a) chamfer finish line
b) functional cusp bevel
c) planar occlusal reduction
d) rounded angles
e) axial reduction
27
the chamfer finish line promotes:
marginal integrity
28
the functional cusp bevel promotes:
structural durability
29
the planar occlusal reduction promotes:
structural durability
30
the rounded line angles promote:
structural durability
31
the axial reduction promotes:
retention and resistance
32
A heavy chamfer provides room for:
thicker ceramic margin
33
The ______ of the heavy chamfer decreases material stress in the margin area
internal rounded angle
34
What is the measurements of a heavy chamfer?
(How deep)
1.0-1.2mm deep
35
What bur is used to accomplish a heavy chamfer?
typically a large round-ended diamond bur
36
Label which chamfer is light and which is heavy:
Left- light
Right- heavy
37
A ______ margin design produces a close to 90 degree angle
shoulder
38
A shoulder margin design produces a close to _____ degree angle
90
39
A shoulder margin design is used primarily for ______ crowns and ______ crowns where thickness of material is important but can also be used for ___ crowns
metal ceramic & all ceramic; zirconia
40
A modified shoulder produces a _____ angle
rounded
41
A shoulder margin is typically created with:
flat-end diamond burs
42
In a shoulder margin design, the angle of the axial wall and finish line is close to 90 degrees and this functions to:
decrease stresses on restoration material
43
A shoulder margin designs primarily used for _____ and ____ crowns
metal-ceramic & all ceramic
44
Label the different margins shown:
Left: shoulder margin
Right: beveled shoulder
45
Some shoulder finish lines can include a bevel at a _____ degree angle
30-45
46
A shoulder with a bevel is often used for _____ and _____
inlays and onlays
47
What type of margin can be used for metal ceramic crowns where there is a metal collar?
beveled shoulder
48
A beveled shoulder margin allows for _____ of metal to ensure marginal fit
adaptability
49
Significant roughness of preparation finish line can prevent:
close adaptation of crown margin
50
Rough margin = ______ = _____
plaque accumulation; recurrent decay
51
Finish line designs vary based on: (3)
1. restoration material
2. location in the mouth
3. desired results
52
The type of tooth preparation in which the finish line forms a 90-degree angle with the unprepared tooth surface:
shoulder
53
The advantage of this margin includes:
-less distortion of crown margins
-provides adequate bulk
-good crown contours
-can attain good esthetics
shoulder
54
The disadvantages of this margin includes:
-marginal adaptation can be affected
-more tooth structure needs to be removed
shoulder
55
Indications of this type of margin include:
-all ceramic crowns
-PFM crowns
shoulder
56
This type of margin is similar to a shoulder but has a bevel placed at the border:
beveled shoulder
57
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 posterior margin for metal-ceramic crowns with a supra gingival margin
beveled shoulder
58
The advantages of this type of margin include:
-to get proper marginal adaptation
-the bulk of the material in border
beveled shoulder
59
The disadvantages of this type of margin include:
-more tooth structure is removed
-less conservative approach
-preparation should be extended apically
beveled shoulder
60
A finish line design for tooth preparation in which the gingival aspect meets the external axial surface at an obtuse angle:
chamfer
61
Indications for this type of margin include:
-cast metal restorations
-lingual margin of metal-ceramic restorations
chamfer
62
Advantages of this type of margin include:
-conservative tooth prep
-good marginal adaptation
-provides bulk to the restoration
chamfer
63
Disadvantages of this type of margin include:
-technique sensitive
-any defect in fabrication can lead to unsupported tip of the crown
chamfer
64
Similar to chamfer finish line but comes with a 90 degrees cavosurface angle with a large radius rounded internal angle:
heavy chamfer
65
In cases of metal restorations using a chamfer margin, a ____ is added to the finish line
bevel
66
Indications for this type of margin include:
-ceramic crowns
-metal crowns with a bevel
heavy chamfer
67
Advantages for this type of margin include:
-best finish line for a ceramic crown
heavy chamfer
68
Disadvantages for this type of margin include:
-technique sensitive
-little discrepancy can lead to the formation of a lip or unsupported fragile enamel
heavy chamfer
69
Also considered a thin-edge margin or feather-edge:
knife edge
70
Indications for 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
knife-edge/feather-edge
71
Advantages for this type of margin include:
-conservative
-helps in preserving tooth structure
-ideal for marginal adaptation
-useful in gold & metal crowns/restorations as it lets you burnish it to a fine finish
-considered an ideal finish line
knife-edge/feather-edge
72
Disadvantages for this type of margin include:
-distinct or proper finish is not visible
-waxing
-polishing and casting become critical
-overcontouring of restorations to obtain a bulk is a usual complication
knife-edge/feather-edge
73
Crown preparation concerns:
Scientists seem to oscillate back and forth as to whether heat produced during a crown preparation will:
kill the pulp
74
Crown preparation concerns:
It is agreed that the _____ becomes irritated and inflamed during _____
pulp; crown preparations
75
Crown preparation concerns:
A rise in the pulp temperature by ____ degrees significantly increases the chance of _____
10 degrees; pulpal necrosis
76
Crown preparation concerns:
Because of the concerns with overheating the pulp during a crown preparation we should: (7)
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 hand piece, an assistant can use air and small amounts of water to help keep tooth cool.
77
The main cause of postoperative inflammation or necrosis of the pulp is probably the injury of ______, a tissue in direct functional and physiological connection with the pulp
dentin
78
Margin design instrumentation:
For the preparation, what is used? (3)
1. high-speed handpiece
2. air/water spray
3. diamond burs
79
Margin design instrumentation:
For finishing the preparation, what is used? (3)
1. slow-speed handpiece
2. fine diamond burs (possibly some carbide burs)
3. hand instruments
80
Margin design instrumentation:
For caries removal of the crown preparation, what is used? (2)
1. slow-speed with 2, 4 or 6 round bur
2. spoon excavators
81
Burs that function to remove enamel and dentin by grinding it away:
diamond burs
82
Burs that function to remove tooth by shearing it away:
carbide burs
83
______ burs are most efficient, 2-3x faster than _____ burs
diamond; carbide
84
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
Carbide burs
85
_____ can be used to help smooth finish lines
hand instruments
86
Hand instruments that can be used to help smooth finish lines include: (4)
1. chisel
2. hatchet
3. hoe
4. margin trimmer
87
Advantages of full metal crowns:
Gold and many metal crowns are:
soft metals
88
Full metal crowns are _____ to opposing teeth
gentle
89
Advantages of full metal crowns:
metal is strong so:
material can be quite thin
90
Describe the preparations involving a full metal crown:
very conservative preparations
91
Advantages of full metal crowns:
Metals have some antibacterial properties making:
recurrent decay less likely
92
Describe the effects of most gold and full metal crowns on the gingiva:
gentle
93
______ crowns are very durable even if worn through or with an endo access
metal crowns
94
In metal crown if the contact is missing:
you can add material to the contact to re-establish it
95
List the disadvantages of full metal crowns:
ESTHETICS
96
Discuss the margin design for a full metal crown preparation:
Can use knife-edge margin, but usually a light chamfer is recommended (0.3-0.5 mm)
97
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
6 to 10; 20
98
In a full metal crown preparation, axial walls can be reduced as little as ___ but can be reduced more if needed
0.5 mm
99
Discuss the occlusal reduction in a full metal crown preparation:
uniform occlusal reduction depth of 1.0 to 1.5mm following tooth anatomy
100
Nothing is _____ in dentistry except for our tools
sharp
101
In a full metal crown preparation, line angles and corners need to be rounded to prevent:
pressure points and possible fracturing of a restorative material
102
In a full metal crown preparation, rounded preparations make the:
crown fabrication process easier
103
In a full metal crown preparation, prepared surfaces and finish line are smoothed with a fine grit diamond bur, what does this ensure?
Preparation walls are scored, but with a smoother more consistent shape for seating and longevity of the restoration
104
Full metal crown summary:
A) Chamfer finish line: _____
B) Axial reduction: _____
C) Total occlusal taper: _____
D) Occlusal clearance: _____
E) _____ of all line angles
A) 0.3-0.5mm
B) as little as 0.5mm
C) 6-10 degrees
D) 1.0-1.5mm
E) rounding
105
Label the various tooth preparations:
(Left to right)
Metal or all-zirconia
PFM
All-ceramic
106
A relatively new material that is tooth-colored and ceramic-like:
zirconia
107
Zirconia is considered _____ free
metal
108
Zirconia can have similar properties to:
metal
109
Zirconia can be described as very:
hard and tough
110
Compare the appearance of zirconia to natural teeth:
less translucent
111
What material is seen in the following crown?
Zirconia
112
The original zirconia that was very tough and very ugly:
Bruxir
113
Why have new iterations of zirconia been created?
to make zirconia more esthetic
114
What is the problem with making new iterations of zirconia that are more esthetic?
In order to make them more esthetic the strength of the zirconia is reduced
115
Depending on the type of zirconia crown, the preparation can be:
as minimal as a full metal crown prep or as extensive as an all ceramic crown prep
116
Zirconia is rapidly changing still so what is extremely important?
knowing which kind of zirconia your lab is using so you can prep appropriately
117
The more esthetic your zirconia is, the more ______ will be needed
reduction
118
