It is common for patients with orthodontic appliances to sometimes suffer some kind of setback during treatment.
One of the most common is the debonding of a bracket. The solution is to re-bond the bracket in its correct position.
As the teeth are placed in their correct position, it is possible that the arch wire protrudes through the back, causing injuries to the mucosa. If that happens, it would be necessary to cut that excess arch wire.
It is common for the braces or tubes used in orthodontics to rub against the lips and cheek, causing small ulcerations, especially in the first days after placing the appliance. There are materials such as orthodontic wax, to place on top of the appliance in the affected area, and thus protect the mucosa from chafing.
In the case of patients with skeletal anchors, it may happen that some of them become loose and/or infected. If this occurs, the anchor should be repositioned, and the infection removed.