Physical Properties in dental biomaterial 1.pdf

Physical properties are fundamental characteristics that define how dental biomaterials behave under various conditions without involving chemical changes in the material's composition. These properties are intrinsic to the material's structure and directly influence its clinical performance, durability, patient comfort, and overall success in dental applications. Understanding physical properties enables dental professionals to select appropriate materials for specific clinical situations, predict material behavior during manipulation and service, and anticipate potential complications. This comprehensive summary explores the major physical properties relevant to dental biomaterials, including density, color and optical properties, thermal properties, electrical properties, surface properties, and dimensional stability.

1. Presented by
Kareem Youssef Ismaiel
Physical Properties

2. PHYSICAL PROPERTIES
Definition:-
•Properties that are not related force application.

Physical Properties describe the behavior of the material

3. Chapter Content
•Properties related to mass
• Thermal properties
• Electrical properties
•Optical properties

4. I. Properties related to mass:

Density (ρ):
It is defined as mass per unit
volume.
ρ= M/V = Mass/Volume
Units: g/????????????
3

5. Acrylic redin 1.2 gm/ ????????????
3
Fused porcelain 2.4 gm/ ????????????
3
Gold alloys 17 gm/ ????????????
3
Cobalt chromium alloys 8 gm/ ????????????
3
Density of some dental material

6. Dental considerations:
•Denture with lighter weight will help
in retension
_The upper denture is preferably made
from low density
-Base metal alloy is lighter than gold alloy

7. •During casting gold alloy which
have higher density than base
metal alloys is easier
Dental consideration

8. •Temperature:-
It is the properties which determines whether the system is in
thermal equilibrium with other system or not.
II. Thermal properties:
Temperature ≠ amount of heat

9. 1- Melting and freezing temperature
•It is the temperature at which the material
melts or freezes.
• Its Units are º K, F, C
Dental Importance:
Determining
-The melting method used in casting
.-Type of investment materials.

10. 2-Thermal conductivity
It is the quantity of heat in calories per second passing through a
body 1 cm thick with a cross-section of 1 ????????????
2
when the
temperature difference is 1 oC
Unites: Cal/sec/ ????????????
2
/ ( oC/cm)
•Metals are better conductor than non
metal.

11. DENTAL CONSIDERATIONS:
-Metallic denture base material conduct
heat better than non-metallic denture
base
Patient satisfaction by sensation of
temperature differences.

12. •Metalic restoration in deep cavities should
be preceded by a protective base to
protect dental pulp from thermal shock
Dental considerations:

13. Specific heat
It is the quantity of heat needed to raise the
temperature of one gram of the substance 1 oC.
Units: Cal/g/°C

14. DENTAL IMPLICATION
Because of low specific heat of gold alloy so prolonged
heating is unnecessary during casting to avoid evaporation of
the element of low melting point.

15. Thermal properties
Thermal diffusivity (Δ)
Its measure the rate which body of non-uniform
temperature reach equilibrium
Unites: ????????????
2
/sec

16. Dental consideration
1. For metallic restorative materials such as gold or crown or
dental amalgam filling, the low specific heat combined with
the high thermal conductivity create a thermal shock.

17. DENTAL CONSIDERATION
•2. Thermal diffusivity and thickness of a material governs its
insulating properties; So it is more important than conductivity.
-Thickness of remaining Dentin is very important to prevent
thermal pulp shock.

18. Thermal properties
Coefficient of thermal expansion (α):
Is the change of length (L final-L
original)per unit length for 1 oC change in
temperature.

19. DENTAL CONSIDERATIONS:
. Restorative materials should have close match of
coefficient of thermal expansion as the tooth
structure to avoid marginal leakage and percolation.

20. PERCOLATION
• IT is a way for bacteria to bypass your tooth's main layer of
protection the enamel to attack it from within.

21. MARGINAL LEAKAGE
Is the penetration of fluids, bacteria and ions into the space
existing between all restorative materials and cavity walls.

22. DENTAL CONSIDERATIONS:
2- In PFM close match in coefficient of
thermal expansion between Porcelain and
metal is important to allow compressive
bond
3-Close match of coefficient of thermal
expansion between artificial tooth and
denture base to avoid crazing dislodgment
of teeth.

23. Dental considerations:
4- . Wax pattern is subjected to
dimensional changes between working
temperature and room temperature. These
changes should be compensated (e.g. by
using investment with high α).

24. DENTAL CONSIDERATIONS:
5- Investment used with wax pattern
should have high α to compensate wax
pattern and solidified metal contraction
6- Casting metals is subjected to dimensional
changes between solidifying temperature and
room temperature. These changes should be
compensated.

25. Heat of fusion
•It is the amount heat in calories required to convert
one gram of the material from solid state to liquid
state at the melting temperature
Units: Cal/ g

26. Latentheat of fusion
•It is the heat in calories liberated when
one gram of the material changes from
liquid state to solid state.
Importance in dentistry:
-During casting, the metal must be heated 100 °C
more than its melting temperature for proper
casting.

27. III. Electrical properties:
•It is the ability of the material to transmit or resist electric
current.
• Dental considerations:
1. Testing pain threshold of various teeth (electric pulp tester)
2. Testing change in the alloy structure after heat treatment