4: Adhesion and cohesion


Adhesion and cohesion

Figure 4.1 Adhesion and cohesion.


Figure 4.2 Adhesive and cohesive failures of cemented restorations.


Figure 4.3 Adhesion zone between adhesive and substrate (schematic).


Box 4.1 Molecular forces determining cohesive strength of an adhesive
1 The chemical bonds within the adhesive material
2 Chemical bonds due to cross-linking of the polymer(s) within a resin-based material
3 Intermolecular interactions between the adhesive molecules
4 Mechanical bonds and interactions between the molecules in the adhesive

Table 4.1 Basic types of adhesion

Type Characteristics
Specific Molecular attraction between contacting surfaces
Mechanical Adhesion through mechanical interlocking between adhesive and substrate surfaces
Effective Bonding between adhesive and substrate due to a combination of specific and mechanical adhesion

Table 4.2 Bond energies and bond lengths in adhesive forces

Average bond energy
Average bond length
Ionic bond 600 0.25
Covalent bond 550 0.15
Metallic bond 250 0.40

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Jan 1, 2015 | Posted by in Dental Materials | Comments Off on 4: Adhesion and cohesion
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