Can wearing a mouth guard mess up your tooth alignment?

Highly Unlikely: A guard which fits adequately & is worn only a few hours a day (or night) cannot move your teeth. However, an ill-fitting (non-professional) guard can move your teeth, especially if it's worn a significant amount of time. Guards which don't cover all your teeth in one arch or which don't have contact will all opposing teeth can cause some movement also if worn too much. Get a professional one.

Yes: A mouthguard should be custom fit to your dentition or it will exert forces on the teeth that could result in minor tooth movement. These problems occur when new dental work occurs after a pre-existing mouth guard is being used. It is best to bring in your existing night guard to have your dentist evaluate how it fits.

YES and NO: A custom mouthguard made by a dentist would take this under consideration. Otc mouthguards are playing with fire.

Yes: OTC appliances can play havoc w occlusion. Partial coverage ill fitting, or improperly made/adjusted appliances can destabilize teeth. See your Dentist.

Yes: if not developed by a dentist or orthodontist they can fit improperly and thus cause teeth to shift. You should see one of these professionals