The big majority of orthodontics in Britain is carried out with fixed appliances this achieves excellent alignment of the teeth but is often followed by relapse. I think orthodontists are embarrassed about relapse but believe that by retaining the result afterwards they remove the problem.
To prevent re-crowding, the teeth must be held in position by one of the many types of retention available, and the British Orthodontic Society has recently recommended that every orthodontic patient should be advised that they will need to wear a retention appliance for the rest of their life. This can require more work than the treatment itself. There are also concerns about food retention and gum damage with fixed wires, especially if subsequent restorative work is required. Experience suggests that removable retainers are usually dis-guarded within a decade or two. There are clearly problems ahead and who will pay for this?
Concern has recently been expressed recently by periodontists (ref if poss) about the consequences of long-term retention of expanded dental arches. Many orthodontists do this to avoid extractions. The teeth are held in position but the soft tissue forces of the tongue, lips and cheeks remain unchanged resulting in progressive clefting and fenestration of the teeth and bone. Because this type of expansion is now widespread, it is likely to become a major problem, not only for the patients but also of course for the dental insurance companies, which may be why it is rarely discussed.
Orthotropics does not need any retention hence there is little risk of gum damage.