There is no simple answer to this question. Generally, The retention phase should be approximately twice as long as the active treatment period. Thus, if a patient has worn fixed braces for a period of two years, then a retention device should be used for a period of four years to stabilise the treatment results.
The propensity for recurrence, however, varies depending on the different types of malocclusion and temporomandibular disorders. Owing to this, therefore, there is no hard-and-fast rule.
The trend in modern orthodontics is to focus on the so-called “life-long retention” principle, i.e. to aim at the life-long stabilisation of the treatment outcome. To ensure that the teeth remain stable in their corrected position for an entire lifetime, it is also necessary to ensure the life-long stabilisation of this position.
Life-long retention can also be beneficial, irrespective of the likelihood of an orthodontic relapse. Among many patients, we observe crowding in the anterior region, so-called “tertiary crowding” (also known as “late crowding”, “post-adolescent crowding”, or “late incisor crowding”) during the patient’s lifetime.
This occurs more frequently in the lower than in the upper jaw. This kind of crowding is so common that some researchers describe “tertiary crowding” as an “anatomical/physiological phenomenon”.