Materials for indirect restoration Flashcards
for indirect restorations what should the choice of materials be
List 7 material requirements for materials for indirect restoration
Fit well onto prepared tooth
Occlusion with opposing dentition
Describe metals as a crown and bridge material
Gold shell crown next to an amalgam
Amalgam look unsightly
Gold - acceptable restorative material
Gold - highly valued as they signify wealth
Metal And allows in particular are options for indirect restorations
How do we choose materials for indirect restoration
Precious alloys more expensive than non precious
Low stress inlay
Material options would be very different
What are patients in LDI prescribe when they are prescribe a gold crown
Primarily gold with high proportions of silver and copper
Affect properties of materials
Each metal has specific function but also affects physical properties
What is the role of gold
Gold largest component
Dominates colour
Gold rings exchanged - timeless or would decay or degrade
what is the role of copper
White gold to yellow gold to whole variety of shades
Palette of colours
what is role of silver
Companies optimised alloys for crown and bridge work where they play around with composition
describe
Simple triangle
Phase diagram for gold alloys
Top = 100% gold
Bottom right = 100% copper
Bottom left 100% silver
White , whitish , yellowish ,redish
Composition of material is 1 star = yellow gold
for casting alloys
what is the base metals alloys
Tend to be stiffer
Mobile elasticity
Important we have stiff material when covering quadrant or anterior
what is the definition of material biocompatibility
Host centred definition
Patient centred
Dentistry in chairside affects patients
what are biocompatibility issues if material fro crown and bridge
Describe porcelain fused to metal
Second classification called porcelain fused to metals
Metal ceramics
Benefits of metal and benefits of aesthetic of a ceramic
Ceramic outer and alloy inner
Cement bridge in place
Restoration been around for a long time
Describe
Use metal ceramic restoration
Composition
Large gold content
Lager palladium content
Palladium cheaper option than gold
what is the role of indium
Bonding oxide - which porcelain bonds to alloys
what are properties of 1 star casting alloy and V delta SF alloy
Density is different
Metal ceramic restoration
Stable metal framework where we can bake a porcelain veneer
Alloy has or have higher melting temperatures to retain structure and rigidity and temperatures which the porcelain is baked on
How do they work?
Join between two
Achieve a good bond between metal and porcelain
Introduce mechanical retention
Roughen metal framework
Direct chemical bond
Mismatch of coefficient of thermal expansion
Ceramic compresses directly
why’s is it not ideal
Light does not pass through metal
Porcelain
Gum recedes and have grey line present of the gingival margin
what are the optical properties of ceramics vs metal
Image sums up why we are moving away from the metal in the mouth
Light doesn’t pass through metal
Better aesthetics
Get rid of metal and replace with ceramic
describe metal ceramic
Superficially
Aesthetics are perfectly adequate
Good restorations
describe all ceramic
New gold standard are all ceramic material
Absence of metals
Natural translucency and layering
Circle in bottom left
Bette properties - glass ceramics
Highly translucent
Very aesthetics
Infiltrate illumina frameworks
High tech engineering ceramics
Toughness of about 1
Toughness of 9/10
Mechanisms by with metals bend and deform are not present in ceramics
Red line - represent material being pulled apart
As the stress increases, reaches catastrophic failure
Ceramics don’t bend , they break
Strain is a fixed point
Ceramics are governed by flaws by cracks and imperfections
Can be introduced any stage in manufacturing process
Increase fracture toughness or reduce impact of critical flaw
Took glass rods and pull thema part = 45 MPa
Acid ethc to round of flaws and fill resin - strength could go up to 1700 mpA
why are ceramics better than glass
Cracks starts to propagate
Deviate propagation
Crack propagates through glass
what is aluminous porcelain properties
- Difference between ceramic and metal
- Metal coating on right has been replaced with luminous core
- Luminous quite opaque
what are glass ceramics
what is IPS e.MAX USED FOR
DESCRIBE THIS DIAGRAM
Produce fine crystal phase - glassy matrix
Powders
Blocks to pressing or putting it in a CAD CAm machine
Take fine powders and melt them
Not very tooth like , glassy at the moment
Controlled heat treatment
Brings to cylinders which are now tooth shades
Block suitable for cad cam machining
Indications
Limited bridge size
Aesthetics amongst highest of all
Strength in median range
Superior aesthetics
Very successful
Good track record
Describe the CAD/CAM process.
Taking impressions
Digital process extends to manufacturers
Use video fed into processor and sent to milling machine which mills restoration
Heat treated or straight back to patients
what is this
Cerac 3
Right - wand which goes into patient mouth to capture image
Fed into design software
Back right corner - milling machine
Software
Margins
Contact points
Bring in opposing occlusion
Library of typical designs
Make bits invisible
Happy with restoration , then mill it
what is this used for
Burs used in milling machine
Stacks of water spraying around
Square shape fo ceramic block ready to be milled
what is transformaiton toughening
Strength and toughness comes from transformation toughening
Zirconia nickname is ceramic steel
See that zirconia exists in different crystal phases
Pure zirconia as you cool it is monoclinic
Take advantage of this that you can play with the composition
Tetragonal phase can retain at low temperatures
Tetragonal constrained at low temperature
Extra energy into particle by advancing crack converts to monoclinic
Compressive forces oppose and counteract tensile forces on crack
Transformation toughening is described as in presence of energy of cracked front - zirconia particles transforms with slight expansion
list some core ceramics for indirect restorations
Technical ceramics
Use alumina and zirconia
LAVA or sircon
Lots of different zirconia type materials
Much stronger and use it in multi use bridges
Zirconia can see toughness and bend strength are higerh than others
Aesthetics good but nto as good as glass ceramics
Zirconia has excellent mehcncial properties and good aesthetics but glass ceramics have even better aesthetics for translucnecy
Material used in unit bridges particularly posteriorly … zirconia
Left - lithium disilicate
Right - zirconium oxide core with veneer
Glassy matrix with crystals- 400 mpa
Controlling crystal size - translucent material
Core is strong
Veneer is weak
Issues on delamination and bonding between core and porcelain
Unlike metals we don’t have those mechanisms to have a good bond strength
Zirconia monolithic restorations - wear away opposing dentition
Unusual to see zirconia core - likely to use monolithic material
