Hey Genesis,
I am also a 3rd year dental student, and I will try my best to break this one down for ya.
First, chemically speaking, primers are composed of hydrophilic monomers and a solvent (acetone or ethanol). The point of the solvent is to dissolve the monomers and to displace water in the dentin surface. By displacing water, it "allows" the monomers to reach the exposed collagen.
Now lets talk about the other part of the primer, the monomer (usually HEMA). The monomer will contain both hydrophilic as well as hydrophobic properties. It has to be hydrophilic so it will have an affinity for exposed collagen fibers in the dentin tubules. It also must be hydrophobic so it is capable of binding to the hydrophobic adhesive resin.
Without the use of a primer, it would be impossible for the hydrophobic resin adhesive to bind to the hydrophobic dentin tubules. In other words, the objective of priming is to transform the hydrophilic dentin surface into a hydrophobic surface that allows the resin adhesive to penetrate. (...so it PRIMES the dentin ;-) )
You may be getting confused because there are different systems, some of which have the primer and adhesive resin in one bottle. These are known as two-step-etch-and-rinse (This is known as a fifth generation and an example is OptiBond Solo Plus). A primer is in a separate bottle in the Three step adhesives (This is known as a fourth generation adhesive and an example we use at our school is Scotchbond Multi-purpose).
I hope that helps a little.
-Bipster
There is so much information about it in my notes that i just dont get.It even has generations of priming and etching.
