properties of dental materials

Question 1

Heat of fusion is the

Answer 1

heat in calories/joules required to conduct 1gm of material from solid to liquid state at melting temperature.
L=q/m where q=total heat absorbed, m=mass of substance melted

Question 2

physical properties of dental materials

Answer 2

properties not concerned with the application of force:
1. temperature related
2. electrical
3. optical

Question 3

thermal conductivity and where it is significant

Answer 3

how much heat can pass through 1cm of material, in 1 sec, with a temperature increase of 1C. It is important for denture bases and metal fillings.

Question 4

Specific heat and where it is significant

Answer 4

the amount of heat needed to raise the temperature of 1gm of a material by 1C

Question 5

thermal diffusivity

Answer 5

the measure of transient heat-flow and is defined as thermal conductivity (K) divided by the product of the specific heat (Cp) and the density (P)

Question 6

thermal expansion and its applications

Answer 6

the change in length per unit length of a material for 1C change in temperature

-wax patterns –> increasing the coefficient of expansion affects the accuracy of rest
- decrease in volume on cooling of alloy needs to be compensated
- investment and polymorphism of silica
- marginal percolation/leakage