The science of dental materials involves a study of the composition and properties of materials used in dentistry and the way in which these materials interact with the environment in which they are placed

1. Dr. Aiser Kareem
Lecture One
Dental Materials Science
Adhesion

2. What is Dental Materials Science?
• The science of dental materials
involves a study of the composition
and properties of materials used in
dentistry and the way in which these
materials interact with the
environment in which they are placed

3. Dental materials may be used in
three phase of dental treatment:
Prevention
Restoration
Rehabilitation

4. Prevention
1. Materials of brushing and flossing.
2. Fluoride therapy.
3. Fissure sealants.

5. Restoration
a-Filling materials (temporary filling, silver filling, tooth colored filling, gold
inlay, ceramic inlay).

6. b-Materials have soothing and promote healing of the
pulp (calcium hydroxide).

7. c-Root canal treatment (solutions used to clean the
canal, materials which fill the canal like gutta percha,
and sealing paste)

8. d-Crown and onlay.
e-Post and core.
f-Cements.
g-Model of teeth to fabricate restorations (gypsum
products).
h-Impression materials.

9. Rehabilitation
a-Artificial teeth (acrylic, porcelain).
b-Implant (titanium screw).
c-Fixed partial denture materials.
d-Cements.
e-Removable partial denture materials (metal
framework and plastic (acrylic) denture base, or
made entirely of plastic).

10. Forms of matter
Change of state
Matter exists in three forms (solid, liquid, and gas).
The difference in form is mainly due to different in
force that held the atoms together (bonds).

11. Atoms are held together by some forces. These
interatomic bonding forces that hold atoms
together are cohesive forces.
Interatomic bonds may be classified as:
1- Primary bonds.
2- Secondary bonds.

12. Primary bonds
These are chemical in nature.
Ionic bonds: these are simple chemical bonds, resulting from mutual attraction
of positive and negative charges; the classic example is sodium chloride.

13. Covalent bonds: in many chemical compounds, two valence electrons are
shared. The hydrogen molecule is an example of this bond.

14. Metallic bonds: results from the increased spatial extension of valence-
electron wave functions when an aggregate of metal atoms is brought close
together. This type of bonding can be understood best by studying a metallic
crystal such as pure gold. Such a crystal consists only of gold atoms. Like all
other metals, gold atoms can easily donate electrons from their outer shell and
form a "cloud" of free electrons. The contribution of free electrons to this
cloud results in the formation of positive ions that can be neutralized by
acquiring new valence electrons from adjacent atoms.

15. 2.Secondary bonds
In contrast with primary bonds, secondary bonds weaker bonds may be said
to be more physical than chemical, they do not share electrons. Instead,
charge variations among molecules or atomic groups induce polar forces that
attract the molecules.

16. Since there are no primary bonds between water and glass, it is
initially difficult to understand how water drops can bond to an
automobile windshield when they freeze to ice crystals. However, the
concepts of hydrogen bonding and Van Der Waals forces (two types
of bonds that exist between water and glass) allow us to explain this
adhesion phenomenon.

17. Van Der Waals forces: this is due to the
formation of dipole. In the symmetric atoms (e.g.
inert gas) a fluctuating dipole is formed, i.e.
within an atom there is accumulation of electrons
in one half leading to a negative polarity and on
the other half a positive polarity. This attracts
other similar dipoles. A permanent dipole is
formed within asymmetrical molecules, e.g. water
molecule.

18. @dr.aiser_kareem