Uses of Primers in Dentin Bonding Systems

Primers (uses, examples, generation)

The primer is used to displace residual moisture, thus creating a surface upon which the hydrophobic bonding resin can adhere.

The primer assists the adhesive to flow into and penetrate the etched tooth surface.

The primer often contains a hydrophilic portion that interacts with the moisture present in the tooth structure, as well as a hydrophobic end that provides bonding sites for the methacrylate monomers in the bonding resin.

For example, 2-HEMA and HEMA dissolved in acetone or alcohol. Dentin bonding agents are unfilled resins which have a role in formation and stabilization of hybrid layer (micromechanical attachment between resin and conditioned primed dentin).

Even though tags are formed into tubules, bond strength is mainly due to micro mechanical bonding of intertubular dentin.

Clinical longevity of dentin bonding system is not as long as enamel bonding due to high water content.

1st generation:

Uses glycerol-phosphoric acid dimethacrylate.

2nd generation:

Uses chloral substituted phosphate esters of various monomers.

3rd generation:

Three step procedure of conditioning, priming, bonding.

4th generation:

Relies on formation of hybrid layer. Called as self-etching primers as conditioning and priming are combined in one step.

5th generation:

Steps two and three are combined.

6th generation:

One step procedure as all three solutions is in one bottle.

7th generation:

Fluoride releasing bonding agents.