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.
- It derives its present name from the old Italian porcellana (cowrie shell)
- 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
- 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
- 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)
- Most important properties are:
- Flexural strength
- Co-efficient of thermal expansion
- Miscellaneous properties
- 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
- 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
- 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
- Its surface accumulates more plaque than a glazed surface
- Crown margins tend to accumulate plaque, hence harder to clean
They are thin pieces of the material used to recreate the natural look of teeth.
- 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