ceramic
DESCRIPTION
TRANSCRIPT
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CERAMIC Dental Materials
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DEFINITIONS
• Ceramic –• An inorganic compound w/ non metallic properties
typically composed of metallic and non metallic elements
• Dental ceramic – • An inorganic compound w/ non metallic properties
typically composed of O2 and 1 or more metallic or semi metallic elements that is formulated to produce the whole part of a ceramic based dental prosthesis
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4 categories of ceramics
1. Silicate Ceramics2. Oxide Ceramics3. Nonoxide Ceramics4. Glass Ceramics
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Silicate Ceramics
• Amorphous glass phase with a porous structure• Main components:• SiO2• Small quantities of :• Al2O3• MgO• ZrO2
Dental porcelain
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Oxide Ceramics
• Principally contains: • Al2O3,MgO,ZrO2 with either no glass phase or
small content.
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Non oxide Ceramics
• Impractical for dental use• Why?• High sintering temp• Unesthetic color• opacity
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Glass Ceramics
• Are partially crystallized glass• Produced by nucleation and growth of crystals
in glass matrix phase
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Dental ceramics
• May consist primarily of :• Glasses , glass ceramics or highly crystalline
structures• Ceramics are more resistant to corrosion than plastic• Remain stable for a long period of time• Do not react with most liquids, gases • Excellent – fair fracture toughness• Zirconium dioxide > Flexural strength similar to steel
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Dental ceramics
• Biocompatible• Long term color stabbility• Wear resistance• Ability to be formed into precise shapes
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CLASSIFICATION OF DENTAL CERAMICS
Phillips Dental Materials
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Dental ceramics can be classified according to :
• Use or Indication- Anterior- Posterior- Crowns- Veneers- Post and cores- FPDs- Stain ceramics- Glaze ceramics
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• Composition- Pure alumina- Pure zirconia- Silica glass- Leucite-based glass ceramic- Lithia based glass ceramic
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• Processing method- Sintering- Partial sintering- Glass infiltration- CAD CAM- Copy milling
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• Firing temperature- Low fusing- Medium fusing- High fusing
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• Microstructure- Glass- Crystalline- Crystal containing glass
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• Translucency- Opaque - Tranlucent- transparent
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• Fracture Resistance
• Abrasiveness
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Metal Ceramic Prosthesis
• COMPOSITION OF DENTAL PORCELAINS• Most dental porcelains consist of • Kaolin• Silica• Feldspar• Glasses
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Glass modifiers
• Manufacturers employ glass modifiers to produce dental porcelains with different firing temperatures
Categories Firing temperatureHigh fusing 1300oC or aboveMedium fusing 1101 to 1300oCLow fusing 850 to 1100oCUltra low fusing < 850oC
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Feldspathic Porcelains
• Feldspar- main ingredient of classical metal ceramic porcelain. ( crystalline and opaque)
• Chemically designated as K2O.Al2O3.6SiO2
• These ceramics are called porcelains because they contain a glass matrix and one or more crystal phases.
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Other Additives
• B2O3 ( Boric Acid) – behaves like a glass modifier• Alumina – not a true glass modifier but can alter
softening temperature and viscosity• Pigmenting oxides – natural shade of tooth• Iron or nickel oxide – brown• Copper oxide – green• Titanium dioxide – yellowish brown• Manganese oxide – lavander• Cobalt oxide – blue• Opacity– zirconium oxide, tin oxide
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Esthetic potetial
Metal ceramic• 70% of all fixed restorations• Not the best esthetic choice• Dark line at facial margin
All Ceramic• Matches appearance of
adjacent natural tooth• More susceptible to
fracture• Ceramic margin
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Porcelain Condensation
• Supplied as a fine powder to be mixed with water or another vehicle and condensed into desired form
• Dense packing has 2 benefits:1. Lower firing range2. Less porosity• Packing may be achieved through1. Vibration2. Spatulation3. Brush technique
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Drying
• The restoration is placed in an open furnace to be dried.
• Until 480 deg C is reached• Drying stage – 5- 8 minutes• Ensures the remaining water is removed• Dries too quickly – spontaneous breakage • If wet structure is placed onto firing in hot
furnace – steam-crumble-explode
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Sintering of porcelain
• The purpose of firing :• To sinter the particles of powder together
properly to form the prosthesis.• Sintering – process of heating closely packed
particles to a specified temp to densify and strengthen a structure
• After porcelain is preheated, firing cycle is initiated.
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Overglazing and shading
• Natural glazed porcelain is much stronger than ground, rough, non glazed porcelain.
• Glaze – effective in reducing crack propagation within the outer surface.
• Stains and glazes
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Cooling of metal-ceramic prosthesis
• Sudden changes in temperature – fracture• Slow cooling followed by slow opening of
furnace door
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Benefits and drawbacks of metla ceramics
• Stronger and more durable than all ceramic crowns
• Permanent aesthetic quality• Fracture resistance• No abrasion wear• No staining along metal and veneer interface• Less tooth structure is removed to provide
proper bulk for the crown.
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Ceramics for Ceramic Metal Restorations
• 5 requirements:1. Must simulate appearance of tooth2. Fuse at low temp3. Must have compatible thermal expansion
with metals4. Must withstand oral environment5. Must not abrade opposing teeth
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Ceramics for ceramic metal restorations
• Ceramics are composed of crystalline phases in an amorphous , glassy vitreous matrix.
• Glass• They fuse at a lower temp , to prevent metal
from distorting
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ALL CERAMIC PROSTHESIS
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• Castable and machinable glass ceramics• Pressable glass ceramics• Slip cast All ceramic ceramics• Procera Allceram• CAD CAM ceramics
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GENERAL APPLICATIONS OF CERAMICS IN DENTISTRY
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• Ceramics are the best materials to match esthetic complexity of human teeth
• Used for ceramic metal crown• FPD• All ceramic resto• To fabricate denture teeth
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Ceramic metal crowns
• ADVANTAGE:• Better abrasion resistance• More durable• Better adhesion with resin cements
• DISADVANTAGES:• Occlusal adjustment is more difficult• Not for high stress areas
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All Ceramic Crowns, inlays , veneers
• Ceramic veneer – layer of ceramic bonded to the facial surface of a prepared tooth to cover any defaults.
• Custom made , fabricated in lab.