ceramic
What inorganic material is made from metals and non-metals united by ionic and/or covalent bonds?
- high young's modulus and high melting points (strong covalent and/or ionic bonds)
- limited electrical and thermal conductivity (absence of electronic cloud due to directional bond)
- low thermal shock resistance (coefficients of thermal expansion and t
What are the general properties of ceramic?
inert - has no interaction with surrounding soft tissue (biocompatible)
What are the biological properties of dental porcelain?
it does not adhere chemically to dental cements
What are the interfacial properties of dental porcelain?
it is not soluble in oral fluids and resist acid attach; both hydrofluoric acid and stannous fluoride can cause an increase in surface roughness
What are the chemical properties of dental porcelain?
brittle - low DTS and fracture toughness; hard, can cause wearing of opposing dentition
What are the mechanical properites of dental porcelain?
low thermal diffusivity; coefficient of thermal expansion similar to that of enamel and dentin
What are the thermal properties of dental porcelain?
excellent esthetic and color matching; difficult to be stained
What are the esthetic properties of dental porcelain?
-sensitive manipulation technique, requiring skilled operator and special equipment
- firing shrinkage always occurs, so operator should build up the restoration to a bigger size that allows shrinkage
What is the practicability of dental porcelain?
1. inlays and onlays
2. esthetic laminates (veneers) over natural teeth
3. all ceramic - single and short span bridges
4. as veneer for cast metal crowns and FPD (metal ceramics)
5. denture veneers (for complete denture and partial denture use)
6. orthodo
Applications of ceramics in prosthetic dentistry:
- biocompatible as it is chemically inert
- excellent esthetic
- thermal properties are similar to those of enamel and dentin
What are the advantages of dental porcelain?
- high hardness - abrasion to antagonist natural dentitions and difficult to adjust and polish
- low tensile strength so it is brittle material
What are the disadvantages of dental porcelain?
application, fabrication method, and crystalline phase
What is the Craig Classification of porcelain based on?
- metal-ceramic: crowns, fixed partial prostheses
- all-ceramic: crowns, inlays, onlays, veneers, and fixed partial prostheses
- additionally, ceramic orthodontic brackets, dental implant abutments, and ceramic denture teeth
What are the different applications of porcelain under the Craig classification?
- sintered porcelain: leucite, alumina, fluoroapatite
- cast porcelain: alumina, spinel
- machined porcelain: zirconia, alumina, spinel
What are the different fabrication methods of porcelain under the Craig classification?
- glassy (or vitreous) phase
- crystalline phases
What are the different phases of porcelain under the Craig classification?
1. high-fusing >1300 C (>2372deg F)
2. medium-fusing 1100-1300 C (2013-2372deg F)
3. Low-fusing 850-1100 C (1562-2012deg F)
4. ultra-low fusing <850 C (<1562deg F)
What are the different fusion temperatures of porcelain under the Anusavice classification?
1. atmospheric firing
2. vacuum firing (lower % porosity)
What are the different methods of firing of porcelain under the Anusavice classification?
1. Core porcelain (used to form basal layer of jacket crown)
2. dentin or body porcelain (more translucent, used to build the body of crown)
3. enamel porcelain (most translucent, used to form the incisal edges
What are the different types of porcelain according to their clinical applications under the Anusavice classification?
1. feldspars - mixtures of K2O, Al2O3, 6SiO2 and Na2O, Al2O3, fuses when melts forming a glass matrix
2. quartz - SiO2; remains unchanged during firing, present as a fine crystalline dispersion through the glassy phase
3. fluxes - used to decrease sinteri
What are the basic constituents of feldspathic porcelain?
PFM
What kind of crown has been the gold standard for 50+ years?
metal-coping and porcelain (veneer)
What are the two components are PFM crowns?
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T/F: Porcelain to metal bond is chemical and mechanical.
- stronger than porcelain crowns
- can be used for constructing long-span bridges
- good esthetic and less liable to staining
- high wear resistance
- long term clinical durability (2.3-7.5 years)
- less preparation is required in comparison to all-cerami
What are the advantages to a PFM crown?
- sufficient metal bulk (0.3mm) is required for proper rigidity
- metal display could result at the thin marginal area
- using opaque porcelain is essential to overcome the metal color
4. special properties of the metal coping are required for proper resu
What are the disadvantages to PFM crowns?
1. has metling temperature higher than the porcelain firing temp (to avoid sagging at the time of porcelain firing)
2. able to form an oxide layer that provides the chemical bond to porcelain (presence of indium or tin in high noble allows is essential fo
What are the requirements of the metal coping on a PFM crown?
-infiltration (flow) of the fused ceramic into the surface irregularities of the metal coping
-sandblasting of the metal surface using plastic beads during waxing are important for this issue
What allows for the mechanical bonding of porcelain to the metal copings?
- ionic bond between the metal oxide layer and the opaque porcelain
- metal degassing is important for oxide formation removing the surface contaminants and greases
- thin oxide layer (in case of noble alloys) provides stronger bond that the thick one (in
What allows for the chemical bonding of porcelain to the metal copings?
as a result of higher metal contraction
-fused porcelain will be sucked (attracted) more strongly into the metal surface irregularities
-residual compressive stresses will be developed in and strengthen the porcelain
What role does the coefficient of thermal expansion mismatch play in the bonding of porcelain to the metal copings?
certain metal system (electro-forming) requires the application of specific bonding paste before building up the porcelain
What role does the application of a special bonding agent play in the bonding of porcelain to the metal copings?
-powder/liquid buildup
-pressing
-cad-cam milling
-3-D printing
What are the 4 processing methods of PFM crowns?
powder - finely ground ceramic and coloring oxide modifiers
liquid - distilled water and modeling liquid
What are the components used in the powder/liquid buildup?
-laying technique - cervical, body, then incisal
-built up as a wet slurry
-condensation - remove excess water, eliminate voids, establish form
Describe the process used in the powder/liquid buildup?
fuses ceramic particles and reduces air (higher strength, increased translucency)
What happens when the ceramic is fired in an oven under vacuum during the powder/liquid buildup?
similar to "lost wax" for metal
-wax pattern, investing mold, burnout, casting under heat/pressure, and then finishing
Describe the process of the pressed ceramics technique.
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T/F: In the pressed ceramics technique, after you wax up a full contour of a crown, you invest it with a sprue (investing mold).
T
T/F: During the burnout part of the pressed ceramics technique, you melt out and get rid of all of the wax that has been invested.
T
T/F: In sequence, the Cad-Cam milling process goes: imaging, then restorative design, and then milling
T
T/F: In the cad-cam milling process, milling is done by removal, so you can shave down a block using a milling unit.
-automated, computer controlled
- two opposing diamond abrasives do the work
- copious water cooling
- milling cycle is about 10-15 minutes, depending on the material and restoration
Describe how a milling device works when milling a crown:
T
T/F: 3-D printing is done by adding and the most common way to do it is by stereolithography, where a laser point comes down from the top and cures resin in layers.
-location (anterior or posterior because posterior is subject to greater forces and needs to be thicker)
-length of the span (only 1 to 2 pontics long)
-connectors (metal can be 2x2mm, while ceramic must be 4x4mm because it is more brittle)
-large vs. sma
What are the important considerations for FDP/bridges?
- type of restoration (crown vs. veneer)
-supporting surface (enamel, dentin, composite)
-type of ceramic
-expected occlusal load
What are additional considerations for FDP/bridges?
resin bonding and conventional
What are the two luting strategies?
-strong, rigid support
-increased retention for non-retentive designs
-complicated, multistep procedure
-technique sensitive
-materials have limited shelf life
-expensive
veneers, inlays, onlays
-lithium disilicate (e-max)
-conventional retention form, mi
Resin bonding:
-adequate support for stronger materials
-increased retention not needed for most crowns
-simple, familiar technique
-materials less sensitive, expensive
-higher strength materials
-tooth prep highly supportive
-lower expected stresses
-zirconia
Conventional luting strategy: