39: Manipulation and properties of porcelain


Manipulation and properties of porcelain

Figure 39.1 Effect of surface condition and firing regimen on porcelain strength.


Box 39.1 Condensation methods for porcelain slurries
Blotting with a brush or 2 × 2 gauze
Mechanically, by vibration or tapping—latter not recommended
Addition of dry powder to surface
Water addition (gravitation method)—not recommended

Table 39.1 Factors in sintering

Sintering factor Effect
Temperature Determines glass flow and firing shrinkage.
Glass viscosity Lower viscosity improves flow of glass during sintering.
Particle size Range of particle sizes reduces void space; smaller particle sizes increase interparticle contact and more uniform surfaces; affects firing shrinkage.
Surface tension High surface tension increases flow and bridge formation during sintering.
Air pressure Increases density by removing air in voids under reduced pressure.

Table 39.2 Stages in firing of porcelain

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Firing stage Effect of firing
Low bisque Removal of organic matter but minimal shrinkage
Medium bisque Flux flow and shrinkage
High bisque Complete vitrification and surface smoothing
Jan 1, 2015 | Posted by in Dental Materials | Comments Off on 39: Manipulation and properties of porcelain
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