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BOARDs > Prosthodontics: Crown & Bridge > Flashcards

Prosthodontics: Crown & Bridge Flashcards

1
Q

Tooth Prep

A

Occlusal/Incisal reduction:
* Maintain Cuspal Anatomy

Functional Cusp Bevel:
* Secondary Plane
* maxillary: Lingual
* Mandibular: Buccal
* Posterior teeth Only

Axial Reduction
Margin/Finish Line

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2
Q

Occlusal Table

A

Traced from cusp tip to cusp tip

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3
Q

What do we do if theres a cavity interfering with this prep?

A

Remove All Decay
Core Build Up

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4
Q

3 Principles of Tooth Prep

A

Biologic: Health of Oral tissues

Mechanical: Integrity and durability of restoration

Esthetic: Appearance of restoration

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5
Q

Biologic Principle of tooth prep

A

Oral Tissues Health:

Mechanical Injury:
* thinnest gingival tissue: L Molars & B Premolars

Thermal Injury: How close to pulp
* use:
* Water spray
* sharp cutting instruments
* intermittent light pressure

Chemical Injury:
* soaked retraction cord
* certain cements

Bacterial Injury:
* leakage under crown

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6
Q

Mechanical Principle of Tooth Prep: Retention Form Vs Resistance Form

A

Most important principle

Retention Form:
* prevent removal of crown from long axis of tooth prep
* (what holds the crown on, trying to pull off)

Resistance Form:
* prevent removal of crown by apical, horizontal, or oblique forces(occlusal force)

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7
Q

Mechanical Principles of Tooth Prep: Taper

A

Aka Parallelism
*angle of convergence b/w opposite axial surfaces
* smaller the taper=more retention
* ideal= 6-10 degrees

Most operator control

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8
Q

Mechanical Principles of Tooth Prep: Height, Length, Width,

A

Height or Length:
* from occlusal/incisal to crown margin
* Incisors/premolars/Canines=3mm minimum
* Molars: 4 mm minimum

Width:
* MD or BL dimension of base

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9
Q

Mechanical Principles of tooth prep: Height to Base Ratio

A

Height is more important than width
* minimum ratio=0.4
* bigger ratio=taller prep=more tape
* smaller ratio= shorter prep, less retention

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10
Q

If you have a short clinical crown, what mechnical properties would you add to increase retention and resistance?

A

Buccal Grooves=Retention

Proximal Grooves=Resistance

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11
Q

What is the minimum metal thickness required for a Gold Crown?

A

Minimum Metal Thickness: (GOLD Crown)
* Margin=0.5 mm
* Non-contact areas=1.0 mm
* Contact areas=1.5 mm

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12
Q

What is the minimum porcelain thickness for an all ceramic crown?

A

Minimum Porcelain Thickness:
* 1.5 mm

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13
Q

What is the minimum and optimal PFM thickness?

A

Minimal PFM Thickness= Non-contact areas
* 1.5 mm (1.2 mm porcelain, 0.3 mm metal)

Optimal PFM Thickness= Contact Areas
* 2.0 mm (1.5 mm porcelain, 0.5 mm metal)

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14
Q

Reduction vs clearance

A

Reduction:
* amount of occlusal tooth structure removed
* Ideal=1.5-2 mm

Clearance:
* amount of space b/w prepped tooth and opposing
* ideal= 1.5-2 mm

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15
Q

Margin Location

A

Supragingival: Above gingival crest
* promotes periodontal health
* easier to clean

Equigingival:
* at the gingival crest

Subgingival:
* below the gingival crest
* more esthetic=anterior

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16
Q

What are the different types of margins?

A

Featheredge
Light Chamfer
Heavy Chamfer
Shoulder

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17
Q

Featheredge Margin

A
  • Best marginal seal
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18
Q

Light Chamfer Margin

A

0.3-0.5 mm wide

Used for:
* Gold Crowns
* wide gold collars of PFM crowns

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19
Q

Heavy Chamfer Margin

A

1-1.5 mm wide

Used for:
* PFM crowns
* some all ceramic crowns

Lab will onvercontour crown if not given enough room

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20
Q

Shoulder Margin

A

1.0-1.5 mm wide
* maximizes esthetics-no metal shows
* Aggressive prep:

Used for:
* porcelain of PFM restorations
* All ceramic crowns

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21
Q

3/4 and 7/8 Crowns

A

Hybrid b/w onlay and full crown
* conserves tooth structure
* Less margin close to gingiva
* Easier to seat during cementation
* normally gold, but rare now

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22
Q

Crown: Occlusal Schemes

A

Occlusal Point contacts=broad and flat
* prevent wear

Cusp-marginal ridge: seen in
* class 1 occlusion
* unworn teeth

Cusp-fossa:
* class II malocclusion

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23
Q

Hygienic Pontic

A

Aka Sanitary
* Posterior Mandible

Good Hygiene: 2mm space b/w pontic and ridge
* Requires enough VDO/restorative space

Poor Esthetics: Not recommended for anteriors

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24
Q

Saddle Pontic

A

Aka Ridge-Lap
* never use

Bad Hygiene

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25
Q

Conical Pontic

A

Molars
* similar to hygienic but slightly best esthetics

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26
Q

Modified Ridge-Lap Pontic

A

Anteriors
* Good Esthetics

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27
Q

Ovate Pontic

A

Anteriors only
* superior/best esthetics

Requires:
* surgery
* good ridge

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28
Q

Bridge: Connector types

A

Rigid:
* either cast in 1 piece or soldered together

Nonrigid:
* can put together and take apart (puzzle pieces)
* use= No common path of insertion b/w abutments

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29
Q

Bridge: Connectors

A

connect retainer to pontic

PFM Bridges: 3 mm Height minmum

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30
Q

Tissue Management for impressions

A

Fluid Control: Saliva & GCF
* cotton rolls, suction
* Antisialogogues (atropine)

Tissue Displacement:
Retraction cords-stretch circumferential periodontal fibers
Impregnated cords: promote hemostasis
* AlCl=Hemodent
* FeSO4: Viscostat
* Epinephrine
Electrosurgery:
* contraindicated: pacemakers or insulin pumps
* electrode can’t contact teeth

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31
Q

What are the 2 categories of impression materials?

A

Aqueous Hydrocolloids
* water based
* mix powder w/water

Non-aqeuous Elastomers:
* not water based
* do not mix powder w/water

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32
Q

What are the different Aqeous Hydrocolloid Impression Materials?

A

Agar=Reversive Hydrocolloid
Alginate=Irreversible Hydrocolloid

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33
Q

Reverse Hydrocolloid

A

Aka Agar
* Aqueous Hydrocolloid
* High accuracy=duplicate casts

Temp changes
* Heat=softer
* Cool=Hardens

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34
Q

Irreversible Hydrocolloid

A

Aka Alginate
Most Innaccurate

Setting time: 3-4 mins
* Pour w/gypsum within 10 mins

Primary Ingredient: Diatomaceous earth
Active Ingredient: Potassium Alginate

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35
Q

For Irreversible hydrocolloids, how do you increase or decrease setting time?

A

Decrease setting time
* Hot water
* Less water

Increase Setting time:
* cold water
* more water

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36
Q

Imbibition vs Syneresis

A

Imbibition: Water Absorption

Syneresis: Water Loss

Avoid Both in Hydrocolloids (Alginate & Agar)

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37
Q

What are the different types of NOn-aqeous elastomers?

A

Polysulfide rubber
Condensation Silicone
Addition Silicone (PVS)
Polyether

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38
Q

Polysulfide Rubber

A

Water Byproduct

Moisture tolerant:
* hydrophobic
* Syneresis (most prone to drying out)

30-45 mins to pour up

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39
Q

Condensation Silicone

A

Alcohol Byproduct
* shrinks impression when evaporated

30 mins to pour

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40
Q

Polyether

A

Very stable, but easily influenced by water and humidity
* Hydrophilic
* Imbibition (swell up with water(

Very stiff-easy to break teeth on cast

60 mins to pour

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41
Q

Addition Silicone

A

aka PVS (Polyvinyl Siloxane)
No Byproducts

Best of everything:
* fine detail, elastic recovery, dimensional stability

  • inhibited by sulfur in latex gloves and rubber dam

60+ mins to pour

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42
Q

Gypsum

A

Mined as: calcium-sulfate dihydrate

Manufactured w/heat to get rid of water= Calcium-sulfate hemihydrate)

Type 1-5

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43
Q

Type 1 Gypsum

A

Impression Plaster
* mount casts on articular

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44
Q

Type 2 Gypsum

A

Model Plaster

Model for:
* Mouth guards
* essix retainers

Study Models

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45
Q

Type 3 Gypsum

A

Dental Stone

  • Microstone
  • Removable prostheses
  • Diagnostic casts
46
Q

Type 4 Gypsum

A

Dental Stone
* High Strength/Low Porosity
* Low expansion

Best abrasion resistance
Least expansion & Gauging water
fabricate dies

47
Q

Type 5 Gypsum

A

Dental Stone
* High Strength
* High Expansion

Fabricate dies

48
Q

Gauging Water

A

extra water needed to to get a workable mix f material

does not chemically react with gypsum

49
Q

Gypsum setting time & Mixing time

A

20 second vacuum mix or 30 sec hand spatual

Setting time=45-60 mins

50
Q

Noble Metals

A

Gold
Platinum
Palladium

SILVER is not

51
Q

Silver

A

Not Noble Metal
* causes greening of porcelain

52
Q

Gold

A

Noble Metal

Tarnish corrosion resistance

53
Q

Platinum

A

Noble Metal

Strength
* increases melting temp

54
Q

Palladium

A

Noble Metal

Strength

55
Q

Metal Alloy

A

Combine 2+ metals
* greater strength or corrosion resistance

56
Q

High noble alloys vs Noble Alloys vs Base metal alloys

A

High Noble Alloys:
* >/= 60% noble–>at least 40%=Gold

Noble Alloys:
* >/= 25% noble

Base metal alloys:
* < 25% noble

57
Q

Type 1-4 Gold

A

Type 1: 98-99% Gold (Pure Gold)
* soft
* Class V restorations ONLY

Type 2: 77% gold
* Medium
* onlays

Type 3: 72%
* Hard
* Crowns

Type 4: 69%
* Very hard
*RPD castings
* Post & Core
*Clasps
* Bridges

58
Q

How to decrease setting time in Gypsum?

A

HOt water
Less water
Use slurry water
Increased spatula time

59
Q

Compressive Strength

A

Resist fracture during compression
Ex: Occlusal forces

60
Q

Tensile strength

A

Reesist fracture during pulling

61
Q

Flexural Strength

A

Resist fracture during bending

62
Q

Fracture Toughness

A

resist crack propagation

63
Q

What material has the best fracture toughness?

A

Zirconia

Undergoes fracture toughening
* normal tetragonal particles–>monoclinic particles=resist crack propagation

64
Q

Modulus Of elasticity

A

aka Elastic MOdulus

Measures stiffness or rigidity
SLope=Stress/Strain

Steeper the sloper the stiffer the material

65
Q

Brittle

A

Fractures easily w/o substantial dimensional changes

ex: Porcelain

66
Q

What material is brittle?

A

Porcelain

fractures easily w/o substantial dimensional changes

67
Q

Ductility

A

Deforms easily under tensile strength

ex; Wire

68
Q

What dental material is a good example of Ductility

A

wire

69
Q

Malleability

A

Deforms easily under compressive stress

ex: gold

70
Q

What dental material is a good example of malleablity

A

Gold

deforms easily under compressive stress

71
Q

Percentage Elongation

A

Can be burnished
* contact stress > Yield strength
* ex: Gold

72
Q

What material is a good example of percentage elongation?

A

Gold

Can be burnished
* contact stress > Yield strength

73
Q

Coefficient of Thermal Expansion

A

change in size per temp change
* Higher CTE=more tendency to change

Comopsite> MetOl> Tooth> Ceramic

74
Q

Desirable Mechanical Properties of a dental material

A

High Yield Strength:
* does not permanently deform

High Elastic MOdulus:
* does not flex

Casting Accuracy:
* gold is more accurate than base meetal

CTE close to tooth (11.4)

Biologic Compatability

Corrosino Resistance

Minimal wear of oopposing dentition

75
Q

Provisional Crown Fabrication

A

3 M’s
1. Method:
2. Mold:
3. Material:

76
Q

Provisional Crown Fabrication: Method

A

Direct:
* made in patients mouth

Indirect:
* on a cast
* prefabricated

77
Q

Provisional Crown Fabrication: Mold

A

Prefabricated Crown: Different materials:
* polycarbonate
* aluminum
* Stainless steel

Cellulose acetate crown form
* transparent plastic material

Putty or shim

78
Q

Provisional Crown Fabrication: Material

A

PMMA:
* indirect method
* exothermic

PEMA:
* not common

Bis-Acryl Composite
* Direct method

79
Q

Provisional Cements

A

Contain Eugenol:
* inhibits polymerization of resin

REMOVE as much as possible

80
Q

When making a PFM crown, what must be present for the porcelain to bond to the alloy/metal?

A

Monomolecular oxidative layer

81
Q

PFM Crown: Porcealin Layers

A

IN to Out

Opaque Porcelain:
* masks dark oxide color
* porcelain-metal bond

Body/Dentin Porcelain:
* most of the shade
* builds up most of crown

Insical/Enamel porcelain:
* most translucent layer

82
Q

PFM Crown: Porcelain-Metal Junction

A

Anterior teeth: Lingual
* only metal present
* conserve tooth structure

occlusal contacts >/= 1.5 mm away from porcealin-metal junction

83
Q

PFM Failures

A

Adhesive Failures (B/w different materials)

Cohesive Failures: (B/w samer materials)
* porcelain-porcelain= VOIDS
* oxide-oxide if oxide layer is TOO THICK
* metal-metal never happens

84
Q

All Ceramic Crowns: Types

A

Glass-infiltrated Ceramics

Ceramics w/no glass content

85
Q

All Ceramic Crowns: Glass-infiltrated ceramics

A

etched w/hydrofluoric acid
* treated w/silanecoupling agent
* bonded to tooth

86
Q

All Ceramic Crowns: Ceramics w/No Glass content

A

Zirconia or alumina
* luted to tooth with cement

87
Q

Porcelain Veneer Prep

A

Intra-enamel prep: all in eaneml layer; only facial surface

Gingival 1/3 reduction: 0.3 mm
Facial Reduction: 0.5 mm
Incisal Reduction: 1-2 mm

Incisal edge: Shoulder Butt Joint (90)
Gingival margin: Chamfer

88
Q

Maryland Bridge

A

Aka Resin-bonded bridge
* minimal prep
* PFM or porcelain
* bopnd to adjacent teeth

can experience Debonding

89
Q

Munsell Color System

A
  • Hue
  • Chroma
  • Value
90
Q

Hue

A

Color Family
* red, blue, grreen etc

91
Q

Chroma

A

color saturation or intensity

  • dull graying blue or more vibrant pure blue
92
Q

Value

A

Lightness or darkness
* most important

measured from 0(Black) to 100 (white)
* more towards 100=Light version of color
* More towards 0=Dark version of color

93
Q

Metamerism

A

color appears different under different lighting

94
Q

Fluorescence

A

Object emits visible light when in UV light

95
Q

Opalescence

A

Translucent material
* Reflected light=appears blue
* transmitted light=red/orange

96
Q

How to select proper shade and color for crowns?

A
  1. Chroma=Cervical 1/3 of crown
  2. Value=middle 1/3 of crown (most important)
  3. Hue=incisal 1/3 of crown
97
Q

Characterization of a restoratoin

A

Reproduce natural defects
* can add more color and make darker but not reverse

Types:
* Staining
* Glazing

98
Q

Staining vs Glazing

A

Staining:
* Lose Fluorescence
* Increase Metamerism
* Decreases VALUE=make darker

Glazing:
* surface porcelain fill in defects

99
Q

Crown Delivery Steps

A
  1. Shade (esthetics)=confirm the sahde is what you selected
  2. Proximal Contacts: Open-send back; Heavy-adjust
  3. Margins
  4. Fit
  5. R&R Form
  6. Occlusion
  7. Contour (anatomical)
  8. Cement
100
Q

Luting Agents

A

Aka Cements

6 types:
* Zinc Oxide Eugenol
* Zinc Phosphate
* ZInc Polycarboxylate
* Glass Ionomer
* RMGI
* Resin

101
Q

Luting Agent: Zinc Oxide Eugenol

A

Temp cement
* soothes pulp
* Eugenol=inhibits polymerixation of resin

102
Q

Luting Agent: Zinc Phosphate

A

Gold Standard
* Phosphoric acid=irritates pulp
* exothermic rxn: mix on child glass slab

103
Q

Luting Agent: Zinc Polycarboxylate

A

Calcium Chelation
* minimal pulp irritation

104
Q

Luting Agent: Glass Ionomer

A

Adheres to enamel and dentin
* releases Fl

105
Q

Luting Agent: RMGI

A

most commmon used today
* Higher strength and lower solubility than GI

Do NOT use with all ceramic crowns
* except zirconia

106
Q

Resin Cement

A

Most compressive strength
* bonds to dentin

Light cure, chemical cure or dual cure
* light cure=more color stable than dual cure

107
Q

What are the possible crowns used today?

A

Zirconia (Ceramic but no silica (Glass))

Metal: (PFM or Gold)

Lithium Disilicate (aka emax; glass ceramic)

Feldspathic porcelain (Veeners)

108
Q

What crowns do we use RESIN Cement vs Luting Cement?

A

Resin Cement: chemical bond dentin-bond-resin-silane-silica
* Lithium dilicate (emax)= dual cure resin cement
* Feldspathic porcelain (veneers)=light-cure resin cement

Luting Cement: (GI or RMGI)
* Zirconia (cermica but no silica/glass)
* Metal (PFM or Gold)

109
Q

Ditching a die

A

expose margin of prep

110
Q

Die spacer

A

room for cement

111
Q

Why do long span PFM bridges fail?

A

Fracture
* due to porcelains low ductility

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