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BOARDs > Prosthodontics: Crown & Bridge > Flashcards

Prosthodontics: Crown & Bridge Flashcards

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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
Conical Pontic
Molars * similar to hygienic but slightly best esthetics
26
Modified Ridge-Lap Pontic
Anteriors * Good Esthetics
27
Ovate Pontic
Anteriors only * superior/best esthetics Requires: * surgery * good ridge
28
Bridge: Connector types
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
29
Bridge: Connectors
connect retainer to pontic PFM Bridges: 3 mm Height minmum
30
Tissue Management for impressions
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
31
What are the 2 categories of impression materials?
Aqueous Hydrocolloids * water based * mix powder w/water Non-aqeuous Elastomers: * not water based * do not mix powder w/water
32
What are the different Aqeous Hydrocolloid Impression Materials?
Agar=Reversive Hydrocolloid Alginate=Irreversible Hydrocolloid
33
Reverse Hydrocolloid
Aka Agar * Aqueous Hydrocolloid * High accuracy=duplicate casts Temp changes * Heat=softer * Cool=Hardens
34
Irreversible Hydrocolloid
Aka Alginate **Most Innaccurate** Setting time: **3-4 mins** * Pour w/gypsum **within 10 mins** Primary Ingredient: Diatomaceous earth Active Ingredient: Potassium Alginate
35
For Irreversible hydrocolloids, how do you increase or decrease setting time?
Decrease setting time * Hot water * Less water Increase Setting time: * cold water * more water
36
Imbibition vs Syneresis
Imbibition: Water Absorption Syneresis: Water Loss Avoid Both in Hydrocolloids (Alginate & Agar)
37
What are the different types of NOn-aqeous elastomers?
Polysulfide rubber Condensation Silicone Addition Silicone (PVS) Polyether
38
Polysulfide Rubber
**Water Byproduct** Moisture tolerant: * hydrophobic * Syneresis (most prone to drying out) 30-45 mins to pour up
39
Condensation Silicone
**Alcohol Byproduct** * shrinks impression when evaporated 30 mins to pour
40
Polyether
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
41
Addition Silicone
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
42
Gypsum
Mined as: **calcium-sulfate dihydrate** Manufactured w/heat to get rid of water= **Calcium-sulfate hemihydrate)** Type 1-5
43
Type 1 Gypsum
Impression Plaster * mount casts on articular
44
Type 2 Gypsum
Model Plaster Model for: * Mouth guards * essix retainers Study Models
45
Type 3 Gypsum
Dental Stone * Microstone * Removable prostheses * Diagnostic casts
46
Type 4 Gypsum
Dental Stone * High Strength/Low Porosity * Low expansion Best abrasion resistance Least expansion & Gauging water fabricate dies
47
Type 5 Gypsum
Dental Stone * High Strength * High Expansion Fabricate dies
48
Gauging Water
extra water needed to to get a workable mix f material does not chemically react with gypsum
49
Gypsum setting time & Mixing time
20 second vacuum mix or 30 sec hand spatual Setting time=45-60 mins
50
Noble Metals
Gold Platinum Palladium SILVER is not
51
Silver
Not Noble Metal * causes greening of porcelain
52
Gold
Noble Metal Tarnish corrosion resistance
53
Platinum
Noble Metal Strength * increases melting temp
54
Palladium
Noble Metal Strength
55
Metal Alloy
Combine 2+ metals * greater strength or corrosion resistance
56
High noble alloys vs Noble Alloys vs Base metal alloys
High Noble Alloys: * >/= 60% noble-->at least 40%=Gold Noble Alloys: * >/= 25% noble Base metal alloys: * < 25% noble
57
Type 1-4 Gold
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
How to decrease setting time in Gypsum?
HOt water Less water Use slurry water Increased spatula time
59
Compressive Strength
Resist fracture during compression Ex: Occlusal forces
60
Tensile strength
Reesist fracture during pulling
61
Flexural Strength
Resist fracture during bending
62
Fracture Toughness
resist crack propagation
63
What material has the best fracture toughness?
**Zirconia** Undergoes **fracture toughening** * normal tetragonal particles-->monoclinic particles=resist crack propagation
64
Modulus Of elasticity
aka Elastic MOdulus Measures stiffness or rigidity SLope=Stress/Strain **Steeper the sloper the stiffer the material**
65
Brittle
Fractures easily w/o substantial dimensional changes ex: Porcelain
66
What material is brittle?
Porcelain fractures easily w/o substantial dimensional changes
67
Ductility
Deforms easily under tensile strength ex; Wire
68
What dental material is a good example of Ductility
wire
69
Malleability
Deforms easily under compressive stress ex: gold
70
What dental material is a good example of malleablity
Gold deforms easily under compressive stress
71
Percentage Elongation
Can be burnished * contact stress > Yield strength * ex: Gold
72
What material is a good example of percentage elongation?
Gold Can be burnished * contact stress > Yield strength
73
Coefficient of Thermal Expansion
change in size per temp change * Higher CTE=more tendency to change **C**omopsite> Met**O**l> **T**ooth> C**e**ramic
74
Desirable Mechanical Properties of a dental material
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
Provisional Crown Fabrication
3 M's 1. Method: 2. Mold: 3. Material:
76
Provisional Crown Fabrication: Method
Direct: * made **in patients mouth** Indirect: * **on a cast** * prefabricated
77
Provisional Crown Fabrication: Mold
Prefabricated Crown: Different materials: * polycarbonate * aluminum * Stainless steel Cellulose acetate crown form * transparent plastic material Putty or shim
78
Provisional Crown Fabrication: Material
PMMA: * indirect method * exothermic PEMA: * not common Bis-Acryl Composite * Direct method
79
Provisional Cements
Contain Eugenol: * inhibits polymerization of resin REMOVE as much as possible
80
When making a PFM crown, what must be present for the porcelain to bond to the alloy/metal?
Monomolecular oxidative layer
81
PFM Crown: Porcealin Layers
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
PFM Crown: Porcelain-Metal Junction
Anterior teeth: Lingual * only metal present * conserve tooth structure **occlusal contacts >/= 1.5 mm away from porcealin-metal junction**
83
PFM Failures
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
All Ceramic Crowns: Types
Glass-infiltrated Ceramics Ceramics w/no glass content
85
All Ceramic Crowns: Glass-infiltrated ceramics
etched w/**hydrofluoric acid** * treated w/**silane**coupling agent * bonded to tooth
86
All Ceramic Crowns: Ceramics w/No Glass content
Zirconia or alumina * luted to tooth with cement
87
Porcelain Veneer Prep
**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
Maryland Bridge
Aka Resin-bonded bridge * minimal prep * PFM or porcelain * bopnd to adjacent teeth can experience **Debonding**
89
Munsell Color System
* **Hue** * **Chroma** * **Value**
90
Hue
Color Family * red, blue, grreen etc
91
Chroma
color saturation or intensity * dull graying blue or more vibrant pure blue
92
Value
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
Metamerism
color appears different under different lighting
94
Fluorescence
Object emits visible light when in UV light
95
Opalescence
Translucent material * Reflected light=appears blue * transmitted light=red/orange
96
How to select proper shade and color for crowns?
1. Chroma=Cervical 1/3 of crown 2. Value=middle 1/3 of crown (most important) 3. Hue=incisal 1/3 of crown
97
Characterization of a restoratoin
Reproduce natural defects * can add more color and make darker but not reverse Types: * Staining * Glazing
98
Staining vs Glazing
Staining: * Lose Fluorescence * Increase Metamerism * **Decreases VALUE**=make darker Glazing: * surface porcelain fill in defects
99
Crown Delivery Steps
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
Luting Agents
Aka Cements 6 types: * Zinc Oxide Eugenol * Zinc Phosphate * ZInc Polycarboxylate * Glass Ionomer * RMGI * Resin
101
Luting Agent: Zinc Oxide Eugenol
Temp cement * soothes pulp * Eugenol=inhibits polymerixation of resin
102
Luting Agent: Zinc Phosphate
Gold Standard * Phosphoric acid=**irritates pulp** * exothermic rxn: mix on child glass slab
103
Luting Agent: Zinc Polycarboxylate
Calcium Chelation * minimal pulp irritation
104
Luting Agent: Glass Ionomer
Adheres to enamel and dentin * **releases Fl**
105
Luting Agent: RMGI
most commmon used today * Higher strength and lower solubility than GI Do NOT use with all ceramic crowns * except zirconia
106
Resin Cement
Most compressive strength * bonds to dentin Light cure, chemical cure or dual cure * **light cure=more color stable than dual cure**
107
What are the possible crowns used today?
Zirconia (Ceramic but no silica (Glass)) Metal: (PFM or Gold) Lithium Disilicate (aka emax; glass ceramic) Feldspathic porcelain (Veeners)
108
What crowns do we use RESIN Cement vs Luting Cement?
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
Ditching a die
expose margin of prep
110
Die spacer
room for cement
111
Why do long span PFM bridges fail?
Fracture * due to porcelains low ductility

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