Prostho 1 prelims Flashcards
(112 cards)
1
Q
Removing a substantial amount of enamel and dentin
A
Preparing the tooth
2
Q
Biologic considerations of tooth Prep
A
- Preservation of the tooth structure/ Pulpal considerations
- Preservation of the periodontium/ Periodontal consideration
3
Q
Mechanical consideration of tooth preparation
A
Provide retention and resistance form
Structural durability
Marginal integrity
4
Q
Objective of tooth preparation
A
Finished tooth prep should be able to accommodate fixed prosthesis that will not incur mechanical failure such as dislodgement/ removal of the prosthesis, and breakage or fracture
5
Q
Quality of a preparation that prevents restoration from becoming dislodged by forces parallel to the path of placement
A
Retention
6
Q
Causes of failure of crowns and FPD
A
- Dental caries
- Porcelain failure
- Lack of retention
7
Q
Factors to consider when assessing retention for a given Fixed restoration:
A
- Magnitude of the dislodging forces
- geometry of the tooth preparation
- roughness of the fitting surface of restoration
- materials being cemented
- Film thickness of the luting agent
8
Q
Forces that tend to remove the restoration along its path of placement
A
Lesser magnitude (magnitude of the dislodging forces)
9
Q
Forces that tend to seat or tilt the restoration
A
Greater magnitude (magnitude of the dislodging forces)
10
Q
Types of occlusal forces (dislodging forces)
A
- Tipping forces (great magnitude - 150 lbs biting force)
- Twisting or rotational forces (great magnitude - 150 lbs)
- Path-of-insertion forces (lesser magnitude)
11
Q
Restoration move circumferentially around the prepared tooth
A
Twisting or rotational forces
12
Q
Examples of lesser magnitude or path-of-insertion forces
A
- Flossing
- sticky food
- gravity
13
Q
Involves angle, degree of inclination, and line angles of tooth prearation
A
Geometry of the tooth preparation
14
Q
Most fixed dental prosthesis depend on the ___ rather than on adhesion (cement) for retention
A
Geometric form of the preparation
15
Q
Cement is effective only if the restoration has ___
A
Single path of placement
16
Q
In terms of geometry, tooth preparation must be in what shape?
A
Cylindrical
17
Q
what are 2 horizontal cross-sections of the prepared tooth that coincide?
A
- Gingival margin
- occlusoaxial line angle
18
Q
Best retention form is achieved with frictional resistance and cement placed under ___?
A
Shear stress
19
Q
Its ability to withstand being pulled appart
A
Tensile strength
20
Q
These have a tensile strength 4-5 times higher than the filler metal itself
A
Brazed joints
21
Q
Ability of a joint to withstand a forc parallel to the joint
A
Shear strength
22
Q
As joint spacing decreases surface tension __ the tensile strength
A
increases
23
Q
It is formed by 2 cylindrical surfaces constrained t slide along one another
A
Sliding pair
24
Q
The elements are constrained if the curve that defines the cylinder is:
A
- closed
- shaped
25
These prevent movement at right angles to the axis of the cylinder
Closed and shaped curves
26
Maximum retention of a tooth preparation is achieved when:
Tooth preparation has near parallel wals
27
Is defined as the convergence of two opposing external walls of a tooth preparation as viewed in a given plane
taper
28
The angle formed by the extension of those planes occlusally/ incisally
Angle of convergence
29
Angle of the wall in relation to the long axis of the tooth
Inclination
30
RETENTION
Degree of angle of convergence:
Degree of inclination:
Degree of taper:
AC: 6 degrees
Inclination: 3 degrees
Taper: 3 degrees
31
Extra coronal walls angle of convergence best
15 degrees
32
As taper increases, freedom of movement ___ and retention ___
Increases, decreases
33
Divergence of opposing axial walls or wall segments in a cervico-occlusal direction
undercut
34
It prevents the withdrawal or seating of a wax pattern or casting
Undercuts
35
Those with greater coronal surface area provide more resistance to dislodgement
Surface area
36
These are concentrated around the junction of the axial and occlusal surfaces where cohesive failure occurs
Stress concentration
37
Solution for stress concentration
Sharp occlusoaxial line angles should be rounded
38
These have various retentive values that correspond fairly closely to the total surface area of the axial walls with restrictive taper, as long as other factors are kept minimal
Type of preparation
39
Adding grooves or boxes _ retention
increases
40
Retention is __ if the restoration is roughened or grooved
increases
41
How to add grooves and roughness in the tooth preparation
- Air-abrading the fitting surface with 50 um of alumina
- acid-etching of the fitting with certain luting agents
42
For roughness,where does retention failure happen?
Cement-restoration interface
43
Base meta alloys are better retained than less reactive materials with high gold content
Metal coping
44
Most retentive luting agent
Resin cement
45
Greatest to least luting agents
Resin cement, GIC, Zin phosphate/ Polycarboxylate, zinc oxide eugenol
46
Least retentive luting agent
ZOE
47
It resists dislodgement along an axis other than the path of placement
It enhances the stability of the restoration
Resistance form
48
Artificial teeth magnitude or force
26 lbs
49
Fixed bridge magnitude or force
54.5 lbs
50
Natura teeth magnitude or force
150 lbs
51
The restoration is loaded during eccentric contact between posterior teeth
Horizontal or oblique forces
52
Tend to displace the restoration by causing rotation around the gingival margin
Lateral forces
53
This prevents rotation of any areas of the tooth preparation placed in compression called __
Resistance areas
54
Resistance take pace in the relationship between:
- Axial wall taper
- Axial wall height or preparation height
- Preparation diameter
55
Ratio of preparation diameter to axial wall height
PD < AWH
56
Resistance decreases as:
- taper increases
- Preparation height is reduced
- Preparation diameter increases
57
Molar crown preparation axial wall height
At least 3-4 mm preparation height
58
Molar crown taper degrees
6-10 degrees
59
Retentive function of grooves and boxes
- limits the path of placement
- creates resistance areas
60
Grooves and boxes are effective when:
- it is perpendicular to the direction of the applied surface
- u-shaped grooves or flared boxes (v-shaped not preferred)
61
Ability of a fixed prosthesis to resist fracture, flexure, and loosening related to its thickness
Structural durability
62
Bulk of the restoration must be confined to the space created by he tooth preparation to have
- Harmonious occlusion
- Normal axial contours
63
All-ceramic incisal/ occlusal reduction
1.5-2 mm
64
Metal-ceramic incisal/ occlusal reduction
Anteriors - 1.5 to 2 mm
Posterior nonfunctional - 1.5mm
Posterior functional - 1.5 to 2 mm
65
Zirconia incisal/ occlusal reduction
Anteriors - 1.5 to 2 mm
Posterior nonfunctional - 1.5 mm
Posterior functional - 1.5 to 2 mm
66
All cast metal incisal/ occlusal reduction
nonfunctional - 1 mm
Functional cusp - 1.5 mm
67
Gold incisal/ occlusal reduction
Nonfunctional - 1 mm
Functional 1.5 mm
68
The occlusal surface is not parallel with the occlusal table
- not necessary that the occlusal surfaces are reduced the same amount
Malposed tooth
69
More occlusal surface needs to be prepared with the thickness requirement of the eventual restoration in mind
Supra-erupted tooth
70
___ must be duplicated to produce adequate clearance without over shortening the preparation
Basic inclined plane pattern
71
Common mistake in reduction where no resistance formed, and no preservation of tooth structure
Flat occlusal surface
72
A common mistake where there is weak restoration due to thinking and no good functional morphology is achieved
Inadequate clearance
73
___ on the functional cusp provide space for an adequate bulk of material n area of heavy occlusal load
Wide bevel (functional cusp bevel)
74
Plays an important role in securing adequate thickness of the prosthesis
2 plane/ phases in reduction meet
Axial reduction
75
All ceramic axial reduction
Facial - 0.8 to 1 mm (2 planes)
Lingual - cingulum - 0.8 to 1 mm
- lingual fossa (occlusion) 1 mm
76
Meta ceramic axial reduction
1. 25 mm minimum
1.5 mm when possible
77
All cast metal or gold alloy axial reduction
Cervically - 0.3 to 0.5 mm
Towards occlusal - 0.7 to 1 mm
78
Restoration can survive in the biologic environment if the margins are closely adapted to the cavosurface finish line to the preapration
Marginal integrity
79
Degree of seating of the restoration
Marginal adaptation
80
Results to marginal opening
Failure to seat
81
Configuration of the preparation finish line dictates the:
- Shape
- bulk of restorative material in the margin of the restoration
82
It should not be wider than half of the bur used to form it
Chamfer
83
Combines an acute edge with a nearby bulk of metal and exhibits least stress to avoid cement failure
Chamfer
84
It is preferred for laminate veneer restoration and also for cast metal restoration
Chamfer
85
Burs used in chamfer
Round-end diamond or torpedo diamond
86
It provides 90 degrees cavo-surface angle with a large-radius rounded internal angle
Deep chamfer/ heavy chamfer
87
It provides better support for a ceramic crown Nathan the conventional chamfer but not as good as the shoulder
Deep chamfer/ heavy chamfer
88
Finish line for ceramic crown and can be beveled for metal restoration
Deep chamfer/ heavy chamfer
89
Bur for Deep chamfer/ heavy chamfer
Round-end diamond
90
Junction of the tooth preparation and tooth surface
Cavo-surface
91
90 degrees cavo-surface angle and internal angle
Shoulder
92
Require more destruction of tooth structure other than finish line and the 90 degrees internal line angle concentrates stress and conducive to coronal fracture
Shoulder
93
Finish line of choice for all-ceramic crown
Wide-edge provides resistance to occlusal forces and minimizes stress that might lead to fracture of porcelain
Also used for metal-ceramic crowns
Shoulder
94
Not used as a finish line for cast metal restorations
Shoulder
95
Bur for Shoulder
Flat-end tapered diamond
96
Cavo-surface angle is 90 degrees and shoulder width is lessened by the rounded internal angle
Radial shoulder
97
Good support for ceramic restoratin
Radial Shoulder
98
Not used for cast metal restoration finish line
shoulder and radial Shoulder
99
Initial instrumentation of the ledge
Flat-end tapered diamond
100
Small-radius rounded internal angle
End-cutting parallel-sided carbide finishing bur
101
Finishing bur
Specially modified bin-angle chisel
102
Possible to create an acute edge of metal at the margin
Shoulder with a bevel
103
Shoulder with a bevel utilization on the finish line
- proximal box of inlays and onlays
- occlusal shoulder of onlays and mandibular 3/4 crowns
- facial finish line of metal-ceramic restorations where gingival esthetics are not critical
- good finish line for preparations with extremely short walls
104
Flat bevel finish line
Narrow - 0.3 to 0.5 mm
Finishing bevel perpendicular to the path of insertion of the restoration
105
May be used where function is heavy and esthetic requirements are minimal
Contrabevel
106
Permits acute margin of meta at the margin
knife-edge and chisel
107
Used on the lingual surface of the mandibular posterior teeth
chisel
108
Permitted the most complete seating of crown
shoulder
109
Range of bevel degree
30 to 45 degrees
110
0.5 mm above the gingival crest and most favorable reaction to gingiva
Supragingival
111
Placed at the crest of the gingiva but can have site of recurrent decay as it rapidly collects plaque and the margin is rough and easily harbors bacteria
Equigingival
112
0.5 mm beneath the gingival crest with the indications of esthetics, cervical erosion, caries extending below gingiva crest, and short or broken down crowns
Subgingival or intracrevicular
