What bonding attachments to crowns might my dentist use for Invisalign?

If the crown is ceramic or porcelain, then the surface can be roughened, and then etched with hydrofluoric acid. After that one can bond attachments to the crown just as one would with regular tooth enamel.

Bonding to dental porcelain is a sometimes thing.  I have had great success with roughing up porcelain, using a strong acid etch (hydroflouric) and over curing the bonding agent and composite.  Even with the success I have had, I still have attachments come off sometimes.  There is no good answer here. Slow meticulous work is required.  Good luck!

Bonding to crowns is a challenge.  We can rough up the surface and etch with HF gel.  But it is always tenuous.  SOmetimes they last, sometimes they don't.

Bonding to porcelain is very challenging when simply placing something "passively", so the durability is even worse with moving teeth, as pressure or torque is placed in an effort to move the teeth.  More traditional methods are more effective (brackets) or doing the case without buttons on the crown.  The best method is to use a diamond bur to remove the outer gloss of the crown to get the bonding agent to bond better, perhaps even using air abrasion.  Several bonding agents would then be used, but with a very pessimistic outlook.  I would try to do the case without buttons on this tooth or simply redo the crown, but during treatment use a temporary crown that has buttons on it.