You can get a hardened sample of the materials without having any placed into your teeth. You can ask for composite and bond and ask that they be a hardened sample so you can do an oral allergy test on them.

It's called a cheek and gum test. You place the material/s into the mouth between cheek and gum and keep it there for an extended period of time per day. Even if it's just an hour or a couple of hours or so and do this daily for a time and check for reactions.

It may not be full proof, but it's one way of doing it.

You could do it your way too I suppose....see what the dentist thinks. Unfortunately there is the bonding/lining to take into account also. Not just the composite.

I would be inclined to get whatever biocompatiblity tests I could if I were you. Blood serum tests, EAV (voll) testing, whatever combination and that way you can see which material/s show up compatible on most/all tests. There will often be some contradictions, but it does narrow things down.

Again, I have no idea how accurate these tests really are and do they tell the full story? Probably not, but it's at least an avenue you can try.