Although there are many orthodontic issues Invisalign can fix, there are some issues it can't. For instance, if teeth need to be severely straightened, Invisalign may not be able to do that. In addition, if gaps are too big, Invisalign may not be able to fix that either. There are other issues that Invisalign may not be able to fix, which is why it is best to consult with an orthodontist to determine what is the best course of action.