Though purely cosmetic, orthodontics allows you to get a perfect smile and to attain the correct bite that may or may not have any influence on your daily life. This does not belay the fact they there can be complications from such trivial a cosmetic procedure. Infection and weak gums can cause more damage if not seen early by the dentist and a good working relationship/collaboration of the two allows better treatment. Gums and underlying bone structures as well as age and the overall health of the person under treatment should also be kept in sight for any illness can greatly influence the overall outcome of the procedure.
It should not however dissuade you from getting treated for as with any endeavor, there are always risks. The aim by mentioning them is to make people aware of such complications allowing the best possible approach and treatment. It may also be sign of more serious health issues that are reflected by the teeth and gums and may need further medical attention.