Force control, stop mechanism, regulating structure of removable arch adjustment appliance

A removable arch adjustment appliance comprising:

• a removable shell having a plurality of cavities shaped to receive a corresponding plurality of teeth of a patient's dental arch, the removable shell including an interior surface configured to apply forces to the teeth therein to reposition misaligned teeth within the patient's dental arch according to a stage of a treatment plan;
• and
• a transpalatal element comprising a sheet of material coupled to the removable shell, the sheet of material shaped to follow the contours of the patient's palate and arranged to span the patient's palate, wherein the sheet of material includes folds extending a length of multiple of the plurality of cavities in an anterior to posterior direction, wherein the folds have folding radiuses that are configured to provide a non-linear force that expands a space between posterior teeth on each side of the patient's jaw or palate.