1. Bonding
Adhesion:
Bonding between dissimilar materials through
chemical reaction of their atoms and
molecules.
Examples of adhesion:
Denture retention by the adhesive action of a thin
film of saliva between the soft tissue and the
denture base.
Cohesion:
Bonding between similar materials.
Examples of cohesion:
Bonding two pieces of pure gold together under
pressure, results from metallic bond
2. Types of Adhesion
Mechanical Adhesion
(Attatchment)
Chemical (True) Adhesion
- CH2 -
- CH2 - CH – CH2
Coo
Coo
Tooth structure
Restorative
material
Tooth structure
Restorative
material
3. Adhesive:
The material used to produce adhesion.
Adherent: or substrate is
substance to which the adhesive is applied.
N.B. For adhesion to take place,
** Materials being joined must be
in close (intimate) contact
** Adhesive must be applied in
the liquid state to produce a thin
layer.
4. Mechanisms (Types) of Adhesion:
Bonding by one of two mechanisms:
I. Mechanical adhesion (attachment):
By the flow and penetration of a liquid adhesive into
microscopic or sub-microscopic irregularities in the
surface of the adherend or substrate →
Mechanical Interlocking i.e. No actual bond
Examples:
Amalgam, composite,
zinc phosphate cement with the tooth.
