Biomedical Engineering Reference
In-Depth Information
FIGURE 7.8
The major shortcomings of current one-step adhesives.
Glass ionomer is the only material that has the self-adhering property. The pretreatment of dentin
surface with 10% or 20% polyacrylic acid (PAA) cleans the surface, removes the smear layer, and
decalcifies the dentin surface to a depth ranging from 0.5 to 1
m. The glass ionomer adhesive then
infiltrates and mechanically interlocks through the process of hybridization. In addition, a chemical
bond is formed through the ionic exchange between the carboxylic group of the PAA and the
calcium ions, which remain attached to the collagen fibrils [5] .
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7.4 Chemical compositions of contemporary adhesives
Retention of restoration and providing a perfect seal to cavity wall and margin are the prime aims
for the use of adhesives. Micromechanical bond to enamel and dentin is the primary mechanism of
adhesion to tooth structure, which is achieved by the infiltration of the resin monomer into the
acid-etching-created porosities and become interlocked upon its curing [5] . Another mechanism of
bonding is the ion exchange between the acidic monomers and calcium through adding specific
monomers, which are able to react with the hydroxyapatite (HAP) [15] . The adhesion of adhesives
is not only limited to tooth substrates but also it should provide excellent bond to the overlying
resin composite. The chemical compositions of the adhesive systems should provide components
that are able to achieve such goals ( Figure 7.9 ). Resin monomers, solvents, initiators, inhibitors,
and sometimes fillers are the main constituents of adhesive systems [16] .
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