Technique To Strengthen Ceramic
- Ceramic brittle matter and have low tensile strength - this makes it chip of at certain clinical condition.
- Therefore necessary to strengthen ceramic to increase longevity.
1)MINIMISING THE EFFECT OF STRESS CONCENTRATION:
A)DESIGN OF PROSTHESIS:
- Select stronger and tougher ceramic
- Grinding of surface of ceramic restoration should be minimised
- Avoid sharp line angle in tooth preparation
2)DEVELOPMENT OF RESIDUAL COMPRESSIVE STRESS:
In post metal ceramic restoration :
- Metal should have more thermal coefficient of expansion than ceramic
- Induce compressive stress this can withstand fracture
- In all -ceramic : core ceramic have more thermal coefficient of expansion
3)MINIMISING NUMBER OF FIRING CYCLES:
- Repeated firing will result in : weaker and fragile ceramic
- If we reduce the number the number of firing we can strengthen ceramic
4)THERMAL TEMPERING :
- Ceramic is heated to a higher temperature ,once it reaches high temperature its quenched rapidly in silicone oil
- Outer skin will solidify
- Inner surface -molten and shrink :this will try to pull outer surface inward and induce reducial compression stress as outer surface is solidified early
5)ION EXCHANGE /CHEMICAL:
- Effective technique
- Surface of ceramic is composed of sodium
- If its placed in molten potassium nitrate bath and heated to 450 degree celsius for 30 minutes
- Potassium will replace sodium ion and potassium gets entrapped in previously occupied space of sodium ion and it will try to expand but since its constricted space this will in turn develop residual compressive stress.
AIM OF THIS POST :
Today we started with a small introduction to ceramic and we moved directly to see the techniques that can be used to strengthen ceramic firstly from the design of prosthesis ,development of residual compressive stress ,minimizing number of firing cycles ,thermal tempering and finally we learnt about ion exchange technique .hope you found this article to be useful ,if this helped you learn then please do let me know in the comment section below as this would motivate me to post more such content .do stay connected through instagram as well .