Group 2 presentation thermal properties.pdf

Thermal properties of materials

1. Group 2 presentation ;thermal
properties
GROUP MEMBERS
CYNTHIA GITHINJI
NICE NJAMBI
FRANCIS

2. THERMAL PROPERTIES
THIS TOPIC FOCUSES ON RESPONSE OF MATERIALS TO TEMPERATURE
CHANGES
TEMPERATURE CHANGES CAN BE MEASURED by thermometers
,thermocouple ,and tactile sense .
Temp changes may occur during the setting reaction of some
materials during cavity preparations and also the oral environment is
exposed to both hot and cold foods in a cyclic manner
Thermal conductivity –is the quantity of heat passing through a
body one centimeter thick ,within a cross section of one square
centimeter when the temperature difference is one degree
centigrade .its represented in the units of watts /m/s/degree
centigrade.

3. Thermal diffusivity
It’s the rate at which a solid with non uniform temperature reaches a
state of equilibrium .
Its calculated as thermal diffusivity =thermal conductivity /specific
heat capacity times density .units are mm^2/sec
This parameter is important since;
A)prosthesis in the mouth are exposed to non steady state due to
eating and drinking hot or cold substances
B) a 5.5 degrees Celsius Increase in temperature is capable of
causing pulp damage

4. Linear coefficient of thermal
expansion COTE
This is the change in the length per unit of a material when the
temperature Is raised by one degree kelvin .

5. Question 1
Which is not a thermal property in dental biomaterials ?
A)thermal conductivity
B)glass transitional temperature
C)thermal diffusivity
D)specific heat
E)coefficient of thermal expansion

6. Question 2
Cote of dental materials should
A )Waxes demonstrate the lowest COTE
B)is a measure of change in length per unit length for a 1 degree
Celsius change in temperature
C)dental ceramics exhibit the highest cote value
D)should ideally be higher than that of dental tissues
E)none of the above

7. Any questions ?
Thank you for your time