L5 dental ceramics Flashcards
Product made from non-metallic material by firing at a
high temperature
ceramic
white translucent ceramic material made by mixing KAOLIN (clay), QUARTZ (flint), and FELDSPAR
Dental porcelain aka ceramics
More quartz and kaolin = ___
More feldspar = ___
stoneware; glassy porcelain “feldspathic porcelain”
porcelain properties: (3)
- highly esthetic
- stronger; wear resistant
- impervious to oral fluids & biocompatible
PHYSICALPROPERTIES OF CERAMICS
- Intermediate density
- High melting point
- Low CTE
- Excellent flexural strength
mech properties of ceramics
- High modulus of elasticity,
- Compressive strength > tensile strength
chemical properties of ceramics
- Low chemical reactivity
- Low absorption and solubility
heating particles in order to fuse them
together
sintering
- sintering temp: 850-1100deg C
- for crown and bridge veneer ceramic
- for porcelain-fused to metal (PFM)
low fusing (sintering)
CERAMIC: crystal structure is —
GLASS: crystal structure is —
ORGANIZED; UNORGANIZED
___ is a type of glass with a Three dimensional network of silica
porcelain
BASIC CONSTITUENTS: FELDSPATHIC PORCELAIN
- feldspars
- quartz
- fluxes
- kaolin
- metal oxide
basic constituent
- MAIN BASE CONSTITUENT
- Fuses when it melts forming a glass matrix
- Contribute to glossy appearance but lack
strength; brittle
feldspars
basic constituents
- Remains unchanged during firing
- Present as a fine crystalline dispersion through the glassy phase
quartz
basic constituent
- Used to decrease sintering temperature
- Controls temperature
- Na, K, Ca - acts as this
fluxes
basic constituent
- Act as a binder
- We can do away with it because clay is not strong/not good
kaolin
basic constituent
- Provide wide variety of colors
metal oxide
- Most common type of porcelain restoration
- Also known as “Porcelain-Fused to Metal” (PFM)
metal ceramic restoration
parts of PFM that make up the dentin & enamel of porcelain (2)
- core “coping”
- opaque porcelain
part of PFM
- Cast metallic framework
- Must be 0.3mm THICK, at least in areas of the appearance zone, so it looks natural
- CHEAP BUT DIFFICULT TO FABRICATE
core “coping”
part of pfm
- First layer consists of porcelain modified with opacifying oxides
- Masks the darkness of the oxidized metal framework
- Metal-ceramic bond
- Best added in areas needed and readily seen–appearance zone
opaque porcelain
most impt req for good, long-term performance
metal ceramic bond
metal ceramic bond is a result of — by diffusion between
the surface oxide layer on the alloy and porcelain
chemisorption
what increases the bond strength of metal ceramic bond
Roughening of surface interface
what are resistant to oxidizing agents in metal ceramic bond
noble metal alloys
FAILURE OF METAL CERAMIC BONDING
- COHESIVE FAILURE
- ADHESIVE FAILURE
- MIXED F AILURE
type of failure in metal ceramic bonding
- Any combination of the previous failures
mixed failure
type of failure in metal ceramic bonding
- Porcelain-oxide, metal-oxide, metal-porcelain
adhesive failure
type of failure in metal ceramic bonding
- Porcelain-porcelain, metal-metal, oxide-oxide
cohesive bonding
REQS OF CERAMICS FOR METAL-CERAMIC RESTO:
- mimic natural teeth
- fuse at low temp
- have thermal expansion coefficient compatible with alloys
- compatible in oral environment
- have low abrasiveness
COMPOSITION OF CERAMICS FOR METAL-CERAMIC RESTORATIONS
- they are opacifiers
- silica
- alumina
- sodium oxide
- potassium oxide
advantage of gold with alloy
- non-corrosive
- ductile
- cheap but hars to make
advantage of porcelain
insulator so it would protect the pulp from harmful stimulus
PROCESSING OF PORCELAIN OVER METAL CORE
- condensation – to remove excess water
2.build-up - firing / sintering – to fuse porcelain particles
- glazing - to smooth surface
types of porcelain
- opaque porcelain – initial part that mask color of cement
- body / demtin porcelain – for COLOR or SHADE
- enamel porcelain – translucent; for INCISAL PORTION
stages of firing/sintering (3)
- LOW BISQUE STAGE
- MEDIUM BISQUE STAGE
- HIGH BISQUE STAGE
stages of firing
- Particles lack complete adhesion, low amount of shrinkage occur, and very porous.
- Ito yung initial firing when you put the porcelain restoration in the oven
low bisque stage
stages of firing
- Water evaporates with better cohesion to the powder particles and some porosity. Most of the firing shrinkage occurs in this stage.
medium bisque stage
stages of firing
- Fusion of particles to form a continuous mass, complete cohesion and no more shrinkage
high bisque stage
glazing types
- AUTO-GLAZING – rapid heating up to the fusion temperature for 1-2 minutes to melt the surface particles.
- ADD ON GLAZING – applying a glaze to the surface and re-firing
types of all-ceramic restoration
-alumina-based ceramic
- leucite-reinforced ceramic
type of all-ceramic restoration
- developed by McLean in 1965
- aluminous core ceramic used in the aluminous porcelain crown
- high modulus of elasticity and relatively HIGH FRACTURE TOUGHNESS, compared to feldspathic porcelains ⭐️
- All-porcelain crown
- Non-silica based
- Tough but not aesthetically pleasing
alumina-based ceramic
type of all-ceramic restoration
- 45% by volume tetragonal leucite
- higher flexural strength (104 MPa) and compressive strength ⭐️
- increased resistance to crack propagation ⭐️
- Silica-based
- Looks natural, may be translucent
leucite-reinforced ceramic
examples [silica/non-silica based]
- zirconia, alumina:___
- feldspathic, leucite, lithium disilicate: ___
silica; non-silica based
MACHINABLE ALL-CERAMIC MATERIALS types
- soft machining
- hard machining
type of machinable all-ceramic materials
- Requires milling of an enlarged restoration to compensate for sintering shrinkage ⭐️
- Some all-ceramic materials can also be machined in a partially sintered state and later fully sintered ⭐️
- Ceramics that are difficult to machine in the fully sintered state, such as alumina and zirconia
soft machining
hard machining types
- COMPUTER AIDED DESIGNING/ COMPUTER AIDED MILLING (CAD/CAM)
- CEREC AC, SIRONA DENTAL SYSTEM
cerec meaning
Chair-side Economical Restoration of Esthetic Ceramic
hard machining type
- The preparation is optically scanned and the image is computerized
- Restoration is designed with the aid of a computer
- Restoration is then machined from ceramic blocks by a computer-controlled milling machine
CEREC
type of hard machining
- Adjustments are easier
- Produce restorations in one office visit
cad/cam
