It depends on whether you're discussing orthodontic treatment (braces
) or corrective jaw (orthognathic) surgery.
With braces, depending on whether teeth are extracted, it may take 18-24 months, if it's done right. Avoid speedy braces! if you're talking about surgery, it takes about 3 hours, but is still done in conjunction with orthodontic treatment, so the total treatment time is about the same.