What are the problems of using steroids while having fixed orthodontic appliances?

None: The steroids usually have no effect on the orthodontic appliance. You may be more prone to infections however.

Specific meds matter: Please go over your specific questions about steroid use with your orthodontist. Certain steroids may effect the bone remodeling that must take place with orthodontic tooth movement. This issue would be a serious complication of orthodontic treatment. Take care..

Slowing down : Theoretically, steroids could slow down tooth movement. But, I have not observed it in 30 years.

Depends: If you need steroids to treat a disease under the guidance of your md then just keep your mouth extra clean to prevent gum inflamation.

Depends: Anabolic or cortico steroids, and why are they being taken, if for inflammatory disease, the usual precautions are in effect, however I have never observed any differences clinically in all of my years of practice. Osteoblastic/clastic activity may be mitigated, bone density changes may occur, and of course patient would be more prone to infection. But again, never have seen these as a problem.