35 fair hurst cw loc kwood pe ring le rd twiggs sw.
Compressive strength of dental ceramics.
For a metal the compressive strength is near that of the tensile strength while for a ceramic the compressive strength may be 10 times the tensile strength.
However the tensile strength of dental porcelain is very low 20 60 mpa.
This imparts brittle nature to the ceramics 23 24 25 and tend to fracture under tensile stresses.
It has similar thermal conductivity and coefficient of thermal expansion to enamel and dentine and exhibits high compressive strength.
Even the pressure strength of dental ceramics are between 350 550 mpa the draw strength value is 20 60 mpa.
More recently the flexural strength has been reported as 240 mpa compared with a value of 115 mpa for alumina reinforced porcelain oilo 1988.
In addition the surface microcracks caused by various reasons during manufacturing are the starting sites of catastrophic fracture.
In fact the elastic modulus of enamel is about three times greater than that of dentin and depending on the study considered it can be as much as seven times higher.
Alumina for example has a tensile strength of 20 000 psi 1138 mpa while the compressive strength is 350 000 psi 2400 mpa.
Note that the proportional limit ultimate compressive strength and elastic modulus of enamel are greater than the corresponding values for dentin.
Dental ceramics possesses very good resistance to the compressive stresses however they are very poor under tensile and shear stresses 1 11 22.
Compressive strength is therefore a useful property for the comparison of dental amalgam resin composites and cements and for determining the qualities of other materials such as plaster and investments.
Fatigue of dental ceramics in a simul ated oral environmen t j dent res.
Dental porcelain has very stable chemical properties and outstanding esthetics which are unlikely to be influenced by time.
Typical values of compressive strength of some restorative dental materials are given in table 5 1.
65 7 993 997 jul 1986.
Ceramics materials are used in modern dentistry in a variety of different applications including fillings crowns veneers implants and dental brackets.
A value of 152 mpa has been quoted for the modulus of rupture of dicor glass ceramic dentsply international york pn usa adair and grossman 1984.
