cementing a PFM crown

Hi there,

I am going to be cementing a PFM crown to a preped tooth.
We have relyx at our dental school, which is a GIC.

Would anyone advise etching the the prep to open up the dentinal
tubules, so that the GIC can bond by micromechanical and chemical
bonding, or is this theory a load of crap?

What about having the fitting surface of the crown sandblasted,
ultrasonic and dipped in HF solution, then using a silane coupling
agent?

This is a lot of messing about because I would then have to etch the
tooth, use a dentine bonding agent and a chemical cured composite as a
sandwich between the dentine bonding agent and silane coupling agent.

And I guess this would have to be all done under rubber dam.

Any thoughts/ advice appreciated.

.