Following any active orthodontics it is imperative to provide post treatment retention as a part of the treatment plan. Research suggests that 70 per cent of orthodontic cases show signs of orthodontic relapse after a 10 year period.
Relapse is defined as a movement of the teeth from their position post orthodontic treatment. However, relapse can be either due to the inherent initial instability of the orthodontic treatment, such as periodontal fibre remodeling, or due to the continual facial growth and natural soft tissue changes that occur in adulthood. Studies show that crowding due to mesial drift occurs even in untreated occlusions due to these natural changes. The current British Orthdodontic Society guidelines are to provide life long retention following any orthodontic treatment to avoid any unfavourable tooth movements; the concept of retention should form part of the consent process.
Aesthetically limited orthodontics, where the tooth movements are confined to the anterior teeth, using fixed or removable appliances, does not change the posterior molar relationships in an anterior-posterior dimension; therefore, the incisors can be positioned in a potentially unstable soft tissue environment in dentally class 2 or 3 dentitions. For this reason a solid retention protocol is critical to avoid the higher risk of possible relapse. The cases where this is of particular note are:
1) Post treatment over jet. Ideally for post orthodontics the upper incisors should fall under the control of the lower lip. When a class 2 molar relationship is not corrected in an aesthetically limited orthodontics case the patient may have a larger over jet with a lack of control by the lower lip.
2) Inter-canine width. Expanding the inter-canine width to create anterior space is inherently unstable due to violation of the soft tissue space. The exception to this is when the lower canines are already lingually positioned. One therefore needs to limit this as far as possible.
3) In deep bite correction. Stability is achieved when a 135° interincisal angle is achieved with a good contact of the lower incisor edge with the upper incisor cingulum. With a patient who is dentally class 2 or 3 this interincisal relationship is often not possible.
The viewpoint with aesthetic orthodontics is that there can be additional post treatment instability of the aligned anterior teeth in comparison to comprehensive orthodontics, therefore a rigid life time post treatment retention protocol is mandatory with fixed bonded wire retainers as well as a removable vacuum formed clear retainers for nocturnal wear.
References available on request.