Adhesion or cohesion includes an adherend, adhesive, and intervening interface. Adhesive
joints may include one or more interfaces. Adhesion science focuses on understanding
the materials properties associated with formation of the interfaces, changes in the
interfaces with time, and events associated with failure of the interfaces.
The key principles for good interface formation are creation of a clean surface, generation
of a rough surface for interfacial interlocking, good wetting of the substratum by
the adhesive/cohesive materials, adequate flow and adaptation for intimate interaction,
and acceptable curing when phase changes are required for final joint formation.
Much more effort is needed in the future to carefully assess each of these using available
testing methods that attempt to characterize the energetics of the interfaces. Bonding
involves potential contributions from physical, chemical, and mechanical sources but
primarily relies on micro-mechanical interaction for success. Characterization of
the interface before adhesion, during service, and after failure would be much more
useful for future investigations and remains as a great challenge.
Scientists should more rigorously apply techniques such as comprehensive contact angle
analysis (rather than simple water wettability) for surface energy determination,
and AFM in addition to SEM for surface texture analysis.
Copyright 2009 Academy of Dental Materials. Published by Elsevier Ltd. All rights