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Prostho 1 > Prostho 1 prelims > Flashcards

Prostho 1 prelims Flashcards

1
Q

Removing a substantial amount of enamel and dentin

A

Preparing the tooth

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2
Q

Biologic considerations of tooth Prep

A
  • Preservation of the tooth structure/ Pulpal considerations
  • Preservation of the periodontium/ Periodontal consideration
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3
Q

Mechanical consideration of tooth preparation

A

Provide retention and resistance form
Structural durability
Marginal integrity

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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

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5
Q

Quality of a preparation that prevents restoration from becoming dislodged by forces parallel to the path of placement

A

Retention

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6
Q

Causes of failure of crowns and FPD

A
  1. Dental caries
  2. Porcelain failure
  3. Lack of retention
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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
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8
Q

Forces that tend to remove the restoration along its path of placement

A

Lesser magnitude (magnitude of the dislodging forces)

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9
Q

Forces that tend to seat or tilt the restoration

A

Greater magnitude (magnitude of the dislodging forces)

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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)
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11
Q

Restoration move circumferentially around the prepared tooth

A

Twisting or rotational forces

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12
Q

Examples of lesser magnitude or path-of-insertion forces

A
  • Flossing
  • sticky food
  • gravity
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13
Q

Involves angle, degree of inclination, and line angles of tooth prearation

A

Geometry of the tooth preparation

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14
Q

Most fixed dental prosthesis depend on the ___ rather than on adhesion (cement) for retention

A

Geometric form of the preparation

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15
Q

Cement is effective only if the restoration has ___

A

Single path of placement

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16
Q

In terms of geometry, tooth preparation must be in what shape?

A

Cylindrical

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17
Q

what are 2 horizontal cross-sections of the prepared tooth that coincide?

A
  • Gingival margin
  • occlusoaxial line angle
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18
Q

Best retention form is achieved with frictional resistance and cement placed under ___?

A

Shear stress

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19
Q

Its ability to withstand being pulled appart

A

Tensile strength

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20
Q

These have a tensile strength 4-5 times higher than the filler metal itself

A

Brazed joints

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21
Q

Ability of a joint to withstand a forc parallel to the joint

A

Shear strength

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22
Q

As joint spacing decreases surface tension __ the tensile strength

A

increases

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23
Q

It is formed by 2 cylindrical surfaces constrained t slide along one another

A

Sliding pair

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24
Q

The elements are constrained if the curve that defines the cylinder is:

A
  • closed
  • shaped
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25
Q

These prevent movement at right angles to the axis of the cylinder

A

Closed and shaped curves

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26
Q

Maximum retention of a tooth preparation is achieved when:

A

Tooth preparation has near parallel wals

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27
Q

Is defined as the convergence of two opposing external walls of a tooth preparation as viewed in a given plane

A

taper

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28
Q

The angle formed by the extension of those planes occlusally/ incisally

A

Angle of convergence

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29
Q

Angle of the wall in relation to the long axis of the tooth

A

Inclination

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30
Q

RETENTION
Degree of angle of convergence:
Degree of inclination:
Degree of taper:

A

AC: 6 degrees
Inclination: 3 degrees
Taper: 3 degrees

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31
Q

Extra coronal walls angle of convergence best

A

15 degrees

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32
Q

As taper increases, freedom of movement ___ and retention ___

A

Increases, decreases

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33
Q

Divergence of opposing axial walls or wall segments in a cervico-occlusal direction

A

undercut

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34
Q

It prevents the withdrawal or seating of a wax pattern or casting

A

Undercuts

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35
Q

Those with greater coronal surface area provide more resistance to dislodgement

A

Surface area

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36
Q

These are concentrated around the junction of the axial and occlusal surfaces where cohesive failure occurs

A

Stress concentration

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37
Q

Solution for stress concentration

A

Sharp occlusoaxial line angles should be rounded

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38
Q

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

A

Type of preparation

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39
Q

Adding grooves or boxes _ retention

A

increases

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40
Q

Retention is __ if the restoration is roughened or grooved

A

increases

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41
Q

How to add grooves and roughness in the tooth preparation

A
  • Air-abrading the fitting surface with 50 um of alumina
  • acid-etching of the fitting with certain luting agents
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42
Q

For roughness,where does retention failure happen?

A

Cement-restoration interface

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43
Q

Base meta alloys are better retained than less reactive materials with high gold content

A

Metal coping

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44
Q

Most retentive luting agent

A

Resin cement

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45
Q

Greatest to least luting agents

A

Resin cement, GIC, Zin phosphate/ Polycarboxylate, zinc oxide eugenol

46
Q

Least retentive luting agent

A

ZOE

47
Q

It resists dislodgement along an axis other than the path of placement
It enhances the stability of the restoration

A

Resistance form

48
Q

Artificial teeth magnitude or force

A

26 lbs

49
Q

Fixed bridge magnitude or force

A

54.5 lbs

50
Q

Natura teeth magnitude or force

A

150 lbs

51
Q

The restoration is loaded during eccentric contact between posterior teeth

A

Horizontal or oblique forces

52
Q

Tend to displace the restoration by causing rotation around the gingival margin

A

Lateral forces

53
Q

This prevents rotation of any areas of the tooth preparation placed in compression called __

A

Resistance areas

54
Q

Resistance take pace in the relationship between:

A
  • Axial wall taper
  • Axial wall height or preparation height
  • Preparation diameter
55
Q

Ratio of preparation diameter to axial wall height

A

PD < AWH

56
Q

Resistance decreases as:

A
  • taper increases
  • Preparation height is reduced
  • Preparation diameter increases
57
Q

Molar crown preparation axial wall height

A

At least 3-4 mm preparation height

58
Q

Molar crown taper degrees

A

6-10 degrees

59
Q

Retentive function of grooves and boxes

A
  • limits the path of placement
  • creates resistance areas
60
Q

Grooves and boxes are effective when:

A
  • it is perpendicular to the direction of the applied surface
  • u-shaped grooves or flared boxes (v-shaped not preferred)
61
Q

Ability of a fixed prosthesis to resist fracture, flexure, and loosening related to its thickness

A

Structural durability

62
Q

Bulk of the restoration must be confined to the space created by he tooth preparation to have

A
  • Harmonious occlusion
  • Normal axial contours
63
Q

All-ceramic incisal/ occlusal reduction

A

1.5-2 mm

64
Q

Metal-ceramic incisal/ occlusal reduction

A

Anteriors - 1.5 to 2 mm
Posterior nonfunctional - 1.5mm
Posterior functional - 1.5 to 2 mm

65
Q

Zirconia incisal/ occlusal reduction

A

Anteriors - 1.5 to 2 mm
Posterior nonfunctional - 1.5 mm
Posterior functional - 1.5 to 2 mm

66
Q

All cast metal incisal/ occlusal reduction

A

nonfunctional - 1 mm
Functional cusp - 1.5 mm

67
Q

Gold incisal/ occlusal reduction

A

Nonfunctional - 1 mm
Functional 1.5 mm

68
Q

The occlusal surface is not parallel with the occlusal table
- not necessary that the occlusal surfaces are reduced the same amount

A

Malposed tooth

69
Q

More occlusal surface needs to be prepared with the thickness requirement of the eventual restoration in mind

A

Supra-erupted tooth

70
Q

___ must be duplicated to produce adequate clearance without over shortening the preparation

A

Basic inclined plane pattern

71
Q

Common mistake in reduction where no resistance formed, and no preservation of tooth structure

A

Flat occlusal surface

72
Q

A common mistake where there is weak restoration due to thinking and no good functional morphology is achieved

A

Inadequate clearance

73
Q

___ on the functional cusp provide space for an adequate bulk of material n area of heavy occlusal load

A

Wide bevel (functional cusp bevel)

74
Q

Plays an important role in securing adequate thickness of the prosthesis
2 plane/ phases in reduction meet

A

Axial reduction

75
Q

All ceramic axial reduction

A

Facial - 0.8 to 1 mm (2 planes)
Lingual - cingulum - 0.8 to 1 mm
- lingual fossa (occlusion) 1 mm

76
Q

Meta ceramic axial reduction

A
  1. 25 mm minimum
    1.5 mm when possible
77
Q

All cast metal or gold alloy axial reduction

A

Cervically - 0.3 to 0.5 mm
Towards occlusal - 0.7 to 1 mm

78
Q

Restoration can survive in the biologic environment if the margins are closely adapted to the cavosurface finish line to the preapration

A

Marginal integrity

79
Q

Degree of seating of the restoration

A

Marginal adaptation

80
Q

Results to marginal opening

A

Failure to seat

81
Q

Configuration of the preparation finish line dictates the:

A
  • Shape
  • bulk of restorative material in the margin of the restoration
82
Q

It should not be wider than half of the bur used to form it

A

Chamfer

83
Q

Combines an acute edge with a nearby bulk of metal and exhibits least stress to avoid cement failure

A

Chamfer

84
Q

It is preferred for laminate veneer restoration and also for cast metal restoration

A

Chamfer

85
Q

Burs used in chamfer

A

Round-end diamond or torpedo diamond

86
Q

It provides 90 degrees cavo-surface angle with a large-radius rounded internal angle

A

Deep chamfer/ heavy chamfer

87
Q

It provides better support for a ceramic crown Nathan the conventional chamfer but not as good as the shoulder

A

Deep chamfer/ heavy chamfer

88
Q

Finish line for ceramic crown and can be beveled for metal restoration

A

Deep chamfer/ heavy chamfer

89
Q

Bur for Deep chamfer/ heavy chamfer

A

Round-end diamond

90
Q

Junction of the tooth preparation and tooth surface

A

Cavo-surface

91
Q

90 degrees cavo-surface angle and internal angle

A

Shoulder

92
Q

Require more destruction of tooth structure other than finish line and the 90 degrees internal line angle concentrates stress and conducive to coronal fracture

A

Shoulder

93
Q

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

A

Shoulder

94
Q

Not used as a finish line for cast metal restorations

A

Shoulder

95
Q

Bur for Shoulder

A

Flat-end tapered diamond

96
Q

Cavo-surface angle is 90 degrees and shoulder width is lessened by the rounded internal angle

A

Radial shoulder

97
Q

Good support for ceramic restoratin

A

Radial Shoulder

98
Q

Not used for cast metal restoration finish line

A

shoulder and radial Shoulder

99
Q

Initial instrumentation of the ledge

A

Flat-end tapered diamond

100
Q

Small-radius rounded internal angle

A

End-cutting parallel-sided carbide finishing bur

101
Q

Finishing bur

A

Specially modified bin-angle chisel

102
Q

Possible to create an acute edge of metal at the margin

A

Shoulder with a bevel

103
Q

Shoulder with a bevel utilization on the finish line

A
  • 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
Q

Flat bevel finish line

A

Narrow - 0.3 to 0.5 mm
Finishing bevel perpendicular to the path of insertion of the restoration

105
Q

May be used where function is heavy and esthetic requirements are minimal

A

Contrabevel

106
Q

Permits acute margin of meta at the margin

A

knife-edge and chisel

107
Q

Used on the lingual surface of the mandibular posterior teeth

A

chisel

108
Q

Permitted the most complete seating of crown

A

shoulder

109
Q

Range of bevel degree

A

30 to 45 degrees

110
Q

0.5 mm above the gingival crest and most favorable reaction to gingiva

A

Supragingival

111
Q

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

A

Equigingival

112
Q

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

A

Subgingival or intracrevicular

Prostho 1 (1 decks)

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