If I have a crack in my tooth will using whitening products make it worse?

It would not affect the tooth, the other tooth areas will look whiter, we have to do a Restoration that matches the color achieve by the whitening procedure.

Though it won't make the crack worse, per se, it can make the appearance of the crack look worse since the rest of the tooth will whiten. If the crack cannot be seen, whitening will have no impact. I hope this helps!