Adhesive agents are used to bond restorative materials. Dental adhesives provide retention to composite fillings or composite cement. In addition to withstanding mechanical forces, and particular shrinkage stress from the lining resin composite, a good adhesive also should be able to prevent leakage along the restorations' margins. Failure of restorations occurs more often due to inadequate sealing, with subsequent discoloration of the cavity margins, than due to loss of retention. Dental adhesives are based on a twofold adhesion. First, the adhesive adheres to enamel and dentin, and second, the adhesive binds the lining resin composite.
As for the bond to enamel and dentin, micromechanical adhesion is assumed to be the prime bonding mechanism. This is achieved by an exchange process by which inorganic tooth material is replaced by resin monomers that become interlocked in the retentions upon curing. Diffusion and capillarity are the primary mechanisms to obtain micro-mechanical retention.
However, recent self-etch adhesives with a mild PH do not completely expose collagen anymore. An additional mechanism of ionic bonding of acidic monomers and calcium in hydroxyapatite is established. Prolink Universal is such!
