PORCELAIN

Porcelain is a white ceramic containing glass with a glazed surface or white , translucent ceramic that is fired to a glazed state. It is used for construction of crown and bridge. If it is used alone for making crowns, they are called porcelain jacket crowns (PJC).

INTRODUCTION TO CERAMICS

• Derived from a Greek word :keramos
• Keramos literally means burnt stuff or a material produced by burning or firing.
• Ceramics are solid inorganic compounds with various combinations of ionic or covalent bonding
• Ceramics are formed from non-metallic materials fired at a high temperature
• They have more complex crystal structure than metals
• Historically ceramic was used initially for making denture teeth
• Dental ceramics are Hard, Brittle , Incombustible ,Corrosion resistant AND Stable  meaning they do not react with liquids, gases ,alkalis and acids
• Poor conductors of heat and electricity
• They are Light(in general lighter than metals)
• The first fabricated ceramic consisted mainly of kaolin ; such ceramic was weak , porous and opaque
• Kaolin was then blended with silica and feldspar to give extra strength and translucency
• Such materials were given the name porcelain
• Porcelain refers to ceramics composed mainly of kaolin , silica (quartz) and feldspar fired at high temperature.
• In dentistry porcelain is used for making Artificial teeth, Crown, Bridge and veneers.

ETYMOLOGY

• It derives its present name from the old Italian porcellana (cowrie shell)

BRIEF HISTORY

• Porcelain can informally be referred to as “china” or “fine china” in some English-speaking countries, as China was the birthplace of porcelain making
• It was used to make artistic objects and decoration pieces

COMPOSITION

• It contains crystalline ingredients held together in a clear liquid like glass structure.
• Availability :bottle
• Presentation : Fine powder
• Dental porcelain is manufactured from three primary ingredients:

1.Kaolin or china clay(Al2O3.2SiO)2 2H2O

2.Silica( SiO2) in the form of quartz

3.feldspar(K2o.Al2O3.6SiO2)(potassium alumino-silicate)

CLASSIFICATION

• Traditional porcelain are classified according to their fusion temperature as:
• High fusing: 1300-1400
• Used to make denture teeth
• Medium fusing:1093-1260
• Used to fabricate jacket crowns (PJC)
• Low fusing:850-1100
• Used to make the material fused to metal crowns (PFM)

PROPERTIES

• Most important properties are:
• Flexural strength
• Brittleness
• Co-efficient of thermal expansion
• Hardness
• Color
• Miscellaneous properties

BRITTLENESS

• • It is very rigid ,hard and brittle material.
  • Traditional it has
  • Low value of tensile strength:20-40MPa
  • High value of compressive strength:350-550MPa

                                                                                                                         

COLOR

• It was developed for dental use because of its super aesthetics
• Available in range of shades and various levels of translucency
• Aesthetics qualities of porcelain do not deteriorate with time
• Displays excellent color stability
• Matching ceramic color to existing teeth is very critical
• Matching is accomplished using shade guide

MISCELLANEOUS PROPERTIES

• It is completely insoluble in oral fluids and is very resistant to chemical attack
• It is unaffected by the wide variation of pH in the mouth
• It is extremely well tolerated by oral tissues.
• It is Inert and has no interaction with surrounding tissues, completely biocompatible

MAINTENANCE

• Its surface accumulates more plaque than a glazed surface
• Crown margins tend to accumulate plaque, hence harder to clean

PORCELAIN VENEERS

They are thin pieces of the material used to recreate the natural look of teeth.

NEW ADVANCEMENTS

• Zirconium crowns are being used, they are :-
• (1) Extraordinarily tough
• (2)Very strong, can withstand wear and tear.
• 3) from an aesthetic point it is clear and very similar to a natural tooth and reflects light the same way
• (4) Less tooth removal
• (5) Zirconium crowns won’t corrode
• (6) No Metal fuse