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IODC > Materials > Flashcards

Materials Flashcards

1
Q

Ceramic restorations: What are ceramics?

A

Compounds of metallic and non-metallic elements:

most frequently oxides, nitrides and carbides.

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2
Q

Ceramic restorations: What are the traditional ceramics?

A 
China
Porcelain
Bricks
Tiles 
Glasses
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3
Q

Ceramic restorations: What is a ceramic building block made of?

A

Silica

Crystalline (tetrahedra structure) e.g. Quartz, Cristoballite
Amorphous e.g. Alumino-silicate glasses

usually a combo used - mixed oxide glass to strengthen properties

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4
Q

Ceramic restorations: What is dental porcelain primarily a mixture of?

A

Feldspar and quartz

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5
Q

Ceramic restorations: What is the composition of early dental porcelain?

A

Feldspar 73-85%, quartz 13-25%, Kaolin 0-4%

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6
Q

Ceramic restorations: How is feldspathic ceramic supported?

A

It is weak

Support using one of 3 methods:
Metal substructure – PFM
High strength ceramic substructure - zirconia?
Bond to the tooth and therefore use tooth as substructure. Resin Bonded Crown (DBC)

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7
Q

Ceramic restorations: How is metal ceramic produced?

A

Metal substructure – PFM Lost Wax Casting (Metal substructure) - make a mould of the wax, fill with molten metal etc

Ceramic Sintering (Ceramic veneer) with feldspathic ceramic

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8
Q

Ceramic restorations: Why is the ceramic overbuilt?

A

Shrinks in furnace

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9
Q

Ceramic restorations: What are the problems with metal ceramic production?

A

Space

  • 0.5mm for metal substructure
  • 1.0mm for ceramic veneer
  • people don’t cut as much tooth away as needed always

Aesthetics

  • Metal substructure prevents light transmittance
  • Often appear opaque, dead, grey
  • Metal margin can be seen
  • this is all a result of too little space cut away

Metal Ceramic Bond - weak
Metal Ceramic Junction - particularly weak where they meet
Metal Ceramic Compatibility* - check this in lab, need circumferential compressive stresses
Support for Ceramic*
- need to make sure TEC for ceramic and metal are the same to get good. bond

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10
Q

Ceramic restorations: How is the TEC of the ceramic and metal matched?

A

TEC of ceramic must be equal to or slightly less than that of the metal.
Metal = 13-14 ppm/°C
Ceramic = 8 ppm/°C
Therefore add Leucite (23ppm/°C)

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11
Q

Ceramic restorations: What are the indications for PFM?

A

Single unit restorations
Multiple unit bridges
Support for partial dentures

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12
Q

Ceramic restorations: What are the properties of a porcelain jacket crown?

A

Alumina reinforced core
Vita (Vitadur N)

Good aesthetics but opaque core
Strength 80 MPa  (anteriors only)
Tooth reduction
Non-adhesive
Pt foil technique therefore poor marginal fit

GONE

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13
Q

Ceramic restorations: What are the types of high strength ceramic substructure restorations?

A

porcelain jacket crown - 60s

Glass Infiltrated Materials (Early ‘90s)
Lanthanum
- comes in 3 varietie - spinel,l alumina, zirconia

Pure alumina substances
Examples:
Procera All-Ceram (Nobel Biocare)
Vita Al (Vita Zahnfabrik)

Zirconia e.g 3M Lava

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14
Q

Ceramic restorations: What was the strength of sp, al, zr?

A 
Strength (MPa)
PJC = 80-100
In-Ceram Sp = 280-300
In-Ceram Al = 350-380
In-Ceram Zr = 530-550
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15
Q

Ceramic restorations: What are the properties of Zirconia (high strength ceramic substructures)

A

Many available on the market
In-house milling is readily available
Stained prior to sintering
Various translucencies - 50%, high translucency = lower strength, shades A1-D4
Requires sintering after milling (10 hours)
mill it big - shrinks by about 25%
Extended sintering times for veneering ceramics
Can be used as monolithic material - all made from one

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16
Q

Ceramic restorations: What are the problems with the high strength of zirconia?

A

Abrasive to opposing teeth
Initial sintering time
Bond between veneering ceramic and zirconia
Large units have long sintering times
Adjusting / removing / Endodontic treatment

17
Q

Ceramic restorations: What are the indications for zirconia?

A

Changing indications

Strength:
Allows multiple units
less tooth reduction: Monolithic

Aesthetics: Substructure & veneer

Combination work: Support for RPD

18
Q

Ceramic restorations: What are the resin bonded restorations (bond ceramic onto tooth structure)?

A 
Veneers
Dentine bonded crowns
Inlays 
Onlays 
Partial Crowns
19
Q

Ceramic restorations: What materials are used for resin bonded restorations?

A

Feldspthic ceramics
Vita VM7 or Vita MkII CAD material (150 Mpa)

Leucite glass ceramic
e.g IPS Empress and EmpressCAD (180 Mpa)

Newist? - Lithium Disilcate
IPS e.max press and e.maxCAD (400-500MPa)
Shofu LD GC,LiSi press

20
Q

Ceramic restorations: how do resin bonded restorations bond to the tooth?

A

Acid etch bond to enamel
Resin in the middle
HF etch and/or SILANE
Restoration on top

or

total etch wet dentine bonding
resin in middle
HF etch and/or SILANE
Restoration on top

21
Q

Ceramic restorations: What are the lab problems with resin bonded crowns?

A

Refractory Model Production - still relying on sintering process
Duplication of die may compound errors
Lack of supporting structure results in fragile restoration, particularly the margins.

22
Q

Ceramic restorations: What are the limitations of resin bonded crowns?

A

Material is quite weak

Single units only*
Weak, therefore anterior region only*

23
Q

Ceramic restorations: What type of crown lithium disilicate? (iPS e.max)

A

Resin bonded

24
Q

Ceramic restorations: What are the properties of Lithium Disilicate?

A 
Strength: 400 Mpa
Pressed or milled
Substructure for veneer
Monolithic
Resin bonded
Formed using the lost wax process - pressing technique rather than casting
Bonds to the tooth
Provides structural integrity
25
Q

Ceramic restorations: What are the preparation requirements of lithium disilicate?

A

No sharp corners

1.0 -1.5mm reduction

26
Q

Digital dentistry: What can computer aided design be used for?

A

Complete dentures
not as popular for RPD
Models for orthodontics, Invisalign
Articulation

27
Q

Shade assessment: What are the factors of an aesthetic restoration?

A

Shape
Colour
Surface Texture
Translucency

28
Q

Shade assessment: How do you communicate shape of tooth to the lab?

A 
Study cast
Use adjacent teeth
photo
diagnostic wax up - best way (shows Shape & Aesthetics, Tooth Reduction
Occlusal Contacts, OVD)
29
Q

Shade assessment: How do you communicate colour of restoration to the lab?

A 
Subjective Shade Assessment
Colour perceived is determined by:
The Illuminant
The Object
The Observer

Therefore can challenging

Objective Shade Assessment - not as good

  • Shade vision (X-rite) Digital image
  • Vita Easy Shade (Vita) Colourimeter
  • Ikam (DCM) Digital image
  • Beyond (Beyond) Digital image
  • Shade eye (Shofu) Colourimeter
  • Shade scan (Cynovad) Digital image
30
Q

Shade assessment: What are the complications of communicating colour to the lab?

A 
Lighting conditions
Distracting strong colours
Colour variation within individual tooth
Translucency variation
Surface reflection
Individual colour perception
31
Q

Shade assessment: how can you describe colour?

A

Munsell System
Hue
Chroma
Value

32
Q

Shade assessment: What are differences between classic shade guide and 3D shade guide?

A

classic
Shades do not cover entire colour space
Not evenly distributed

3d
Equal distribution
Logical construction

33
Q

Shade assessment: How do you communicate surface texture?

A

Photo

Study cast

34
Q

Shade assessment: What is the munsell system of colour?

A

Hue - colour family - use L and R tabs
Chroma - colour saturation (how pigmented) - work down value group
Value - lightness or darkness of colour - work across value groups

35
Q

Shade assessment: Shade taking tips?

A 
Hydrated teeth
Switch off operating light
Multiple light source – daylight corrected
Multiple opinions
Work quickly
36
Q

Shade assessment: EXAM QUESTION Why do we need to communicate with the lab well?

A

Planning – Wax-up? Occlusion?
Patient communication
Pre-operative impression
Working Impression
Opposing Impression - see occlusal contacts
Inter occlusal record - to locate two models together
Lab card. - design features of restoration
Shade: Shape Translucency, Surface texture

IODC (8 decks)

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