Orthodontic retainers: now you have finished your orthodontic treatment how do you manage long-term post-orthodontic retention?

Why are retention and stability important?

Retention following active orthodontic tooth movement is necessary for several reasons:

The first three points are the traditional reasons for recommending retention following orthodontic treatment; however managing continued growth and ageing are now considered as equally important, because both the BOS^2,3 and the Department of Health (DoH)⁹ recognize that the positions of teeth do alter throughout life. It is therefore recommended that to retain straightened teeth, a patient should continue to wear their retainers for the rest of their life or for as long as they wish their teeth to remain straight. Having acknowledged this, however, there is little guidance on how to do this over a prolonged period, after active orthodontic treatment.

Some of the most pertinent research to this subject area over the past few decades has been undertaken by Little et al in the 1980s.^6,7,10 This team from the US assessed stability and relapse of lower labial segment alignment in premolar extraction and non-extraction cases up to 10–20 years post-retention. In the premolar extraction case group, 70% had unsatisfactory lower labial segment alignment at 10 years post-retention⁶ and only 10% of cases were considered to have ‘clinically acceptable’ mandibular alignment 20 years post-retention.⁷ Little et al concluded that cases responded after treatment in an unpredictable manner with no obvious pre-treatment variables (clinical or radiographic) that would predict future success relating to orthodontic stability.^7,10

It is important to understand that teeth, especially the lower labial segment, may move with age irrespective of orthodontic treatment. This has been shown in a study that examined tooth movement 12 years after orthodontic treatment in patients with and without retainers.¹¹ The authors concluded that approximately 25% of incisor displacement was due to natural growth, and not from orthodontic relapse. It is also necessary to consider society's knowledge and expectations on the stability of orthodontic treatment results; do patients/parents want perfection or is the return of a limited amount of irregularity acceptable? A cross-sectional survey undertaken in Switzerland explored this, and found that the stability of treatment results was very important in people deciding about a prospective course of treatment, but their knowledge on post-orthodontic retention was very varied and sociocultural factors had a significant influence on this.¹²

Wouters et al developed a clinical guideline for orthodontic retention for general dental practitioners (GDPs) in the Netherlands.¹³ Their recommendations are mostly based on research evidence, expert opinion and clinical experience, and were developed following a systematic review of the literature that included 15 studies.¹⁴ Their guidance is pragmatic and well considered, but is specific to the Netherlands. It is important to consider the particular challenges of provision in different geographic regions. In the UK, orthodontic treatment for young people is predominantly offered through a government-funded healthcare service and this article therefore aims to provide guidance on long-term orthodontic retention to UK-based practitioners working in the NHS.

Current evidence for type of retention appliances and retention regimens

There are various types of removable and fixed orthodontic retention appliances, and the decision on which type to provide is usually made by the clinician based on the pre-treatment malocclusion, the quality of the result and following careful discussion with the patient to decide which type of retainer they are able and willing to maintain. In the UK, clear plastic removable retainers are the most commonly used method of retention, and this is sometimes in conjunction with fixed bonded retainers.¹⁵

The advantages of clear plastic retainers are that they are relatively inexpensive,¹⁶ patients are less embarrassed to wear them, they can be removed for cleaning, and are largely used part-time. There is clear evidence that demonstrates these retainers are effective in maintaining incisor alignment.¹⁷ The main drawback of these appliances, however, is that they rely on the patient wearing them as instructed.¹⁸ Fixed bonded retainers are also commonly used and have been shown to successfully maintain mandibular labial segment alignment upto 4 years after the completion of treatment.¹⁹ Evidence is needed, however, to determine how well they perform in the longer term. Both removable and fixed retainers have been shown to result in gingival inflammation and increased plaque deposits in the absence of adequate dental hygiene measures, which challenges long-term dental health.^19,20

Fixed bonded retainers, while reducing the need for patient compliance, do have potential disadvantages. They are more costly and technique sensitive to fit, they are often difficult to repair and there have been reports of significant and detrimental tooth movement if they get damaged or distorted without the patient noticing or are not passive when bonded.^21,22

There have been several studies assessing different types of retainers^{16,17,19,20,23,24,25,26,27} and different retention regimens,^28,29,30 but the most recent Cochrane review concluded that there is inadequate high-quality evidence and further high-quality trials are needed.¹⁴

Due to this lack of evidence for managing retention, retention appliance selection and regimens are often based on clinician experience and preferences, using a patient-centred approach to ensure the patient understands their responsibilities for wearing, looking after and maintaining their retainers.³¹ It is essential that patients are engaged with the process of retainer wear from the outset. First, this forms a critical part of adequate informed consent at the start of treatment,³² and secondly with removable and fixed retention, there is heavy reliance on patient adherence, whether it be remembering to wear removable retainers or keeping fixed bonded retainers clean and getting them checked regularly. This is particularly difficult long term.

Difficulties with long-term retention management

One of the difficulties with recommending a long-term retention management strategy is that there is a lack of evidence to base this on. In an opinion piece, McCrory reported that it could take 100 years to develop an adequate evidence base on long-term retention owing to the inherent difficulties with doing clinical research with long follow-up periods, such as high attrition rates, migrating populations and the associated significant cost implications.⁴

A significant part of the acceptance of retention is patient adherence with the instructions given, and the quality and clarity of the instructions themselves. A recent systematic review and meta-analysis assessing compliance with removable appliances and adjuncts reported that patients routinely overestimated duration of appliance wear by approximately 5–6 hours daily, and this was often the case even when patients were aware they were being objectively monitored.¹⁸ The reasons for poor adherence could be for a number of reasons including appliance discomfort, embarrassment or long-term fatigue with the rigours of retainer usage. Adherence is also likely to be affected by other factors such as patient age, gender and stage of treatment,³³ with younger patients and those early in treatment tending to comply better. Specific life stages, such as going to university or young adulthood, may particularly challenge retainer wear. It is therefore necessary to guide and inform patients on a pragmatic approach to retainer wear for the long term. In some cases, patients may need to understand that orthodontic treatment may not be for life, and further future treatment may be required.

Who takes responsibility for the long-term management of retainers is a particularly contentious issue. Should it be the patient, their GDP or specialist orthodontist? Most orthodontists in primary and secondary care in the UK will carry out active monitoring of patients in retention up to 1 year after active treatment, following which the patient is usually discharged back to their GDP. However, a cross-sectional questionnaire-based audit assessing GDPs knowledge of orthodontic retention in England found that most GDPs would like further training on retention, and that insufficient knowledge, as well as financial and time constraints, were factors affecting their ability to maintain/provide retainers.³⁴

Even if the initial treatment was provided by the NHS, at no personal cost to the patient, it is most likely that the ongoing maintenance of retainers will have cost implications. Even though these costs may not be substantial, patients should still be made aware of this before they start treatment.

Suggested guidance on management of long-term retention

Clear informed consent should be sought from the outset of a course of orthodontic treatment about the need for long-term retention, the likely type of retention appliance(s) and the commitment involved in maintaining the orthodontic result. If fixed bonded retainers are required, it is important to discuss this from the outset. It is also important to highlight the option of ‘no treatment’ if patients feel they will not want to comply with long-term retention. All aspects of retainer wear need to be discussed, including the management of breakages and any potential costs that may be incurred in the longer term.

A comprehensive set of instructions regarding long-term retainer wear should be provided at the end of a course of treatment, ie a clear and comprehensive discharge letter to the patient and their GDP so the patient is able to self-regulate their retainer wear in the long term, and GDPs are aware of the type of retention appliance(s) and regimen prescribed. This should include:

As there is no evidence base on which to rely when prescribing orthodontic retention, there is no single regimen that can be applied. In view of this, other factors may be used to support a rationale for a specific retention regimen. The amount of tooth displacement at the start of treatment and the presence of significant rotations of the teeth may require more intensive retainer wear, as will pre-treatment spacing, deep bites and significant amounts of arch expansion during treatment.

Clear plastic retainers are closely moulded to the dental arch and any movement of the teeth can be felt by the patient as tightness on insertion. It is best to fully instruct each patient that the appropriate amount of retainer wear is that which means their retainer should never feel excessively tight when re-inserted, irrespective of the time since the last time the appliance was worn. There will be a different amount of wear for each patient and the duration per day and for how many years they will need to wear the retainers will also be unique to each individual. A clear view of the likely outcome of poor retainer wear should be documented before the patient is discharged from the orthodontist's care, and explained to the patient.

One useful strategy for supporting patients is to provide them with duplicate models at their debond so that if their retainers become damaged or lost in the future, they do have a template of their end-of-treatment tooth position. Consideration can then be given to remaking the retainers based on the model if the tooth position is reasonably similar to their finish position. In this way, their new retainer can be used as a positioner to correct any minor tooth movement. This is particularly useful for those patients who cannot return to their original orthodontic provider. An alternative strategy that could be considered, and is already used by several clinicians, is to provide patients with two sets of removable retainers at debond as a routine.

Each individual patient will require a different regimen, and a detailed discussion between the patient, their parent (if appropriate) and the orthodontist must be part of the discharge process. The suggested wear should be individualized for each patient and consented. The only valid assessment of orthodontic relapse, however, is whether the patient feels tightness on re-insertion of retainers after a period of non-wear. The only person who can fully assess this is the patient themselves, and they should be instructed how to assess the success of their own retainer wear. This testing of the length of time a retainer needs to be worn per day/week/month in order to prevent tightness on re-insertion is critical to successful retainer wear and the process of ‘titrating’ the amount of wear to the patient's needs is important in preventing relapse. Patients should maintain well-fitting retainers indefinitely, but the frequency of wear can be titrated depending on the ‘feel’ of the retainer on insertion and should be regularly reviewed by the patient. This practice should be employed with removable retainers whether or not a fixed retainer is present.

It is important to recognize that there is a difference in the maintenance of fixed and removable retainers, and it is not uncommon for patients to request bonded retainers. Fixed retainers can be considered a useful adjunct or alternative to removable retainers when indicated owing to the pre-treatment malocclusion, for example spacing or severe rotations, or in cases of severe loss of periodontal support, or cleft lip and palate cases. They may also be considered when teenagers are not willing to comply with removable retainers (eg when they go to college). However, the decision regarding fixed retention requires full informed consent, including risks and benefits, as well as any associated future costs to the patient/their parents in terms of review, maintenance and replacement. While the maintenance of removable retainers is more the responsibility of the patient, clinicians will have a greater responsibility for fixed bonded retainers. Removable retainers placed over fixed retainers are also useful as a safeguard. If the removable retainer is being intermittently inserted any breakage of the fixed retainer may be noticed before there has been any visible unwanted tooth movement because the patient may be able to ‘feel’ tightness before they can see displacement. In this way, a patient can be alerted to a possible issue with their fixed retainer before the problem becomes significant.

Should a fixed bonded retainer be indicated, but the patient chooses not to wear this, they should be aware that it may be necessary to wear their removable retainer significantly more.

If patients choose to discontinue their retainer wear or wear their retainers less than instructed, there is no guarantee the teeth will remain in the position achieved at debond, and the patient is likely to get a degree of relapse. It is important that they understand that further orthodontic treatment to correct any relapse is unlikely to be funded on the NHS in the UK.

Recall intervals

Retention appliances are medical devices, and therefore are routinely reviewed for 1 year after completion of active treatment by the orthodontic provider in NHS practices, community clinics and hospitals as part of their course of NHS orthodontic treatment. The reason that retainers are reviewed within the first year after debond is to ensure that patients understand the importance of the retention phase and are complying with the regimen, and it allows the practitioner to check that the retainers are being maintained appropriately. Another study showed that more frequent retainer check appointments had a positive effect on patient compliance with removable retainer wear.³⁵

After this time, it is reasonable that arranging review and long-term maintenance of retainers should be the responsibility of the patients themselves. This may be in conjunction with their GDP or with a local specialist orthodontic practice, and a recent publication discusses some of the common problems with retainers and provides advice on how these can be managed.³⁶ Financially, it does not currently appear to be feasible for GDPs to review patients for retainer reviews over their lifetime, given time constraints in busy NHS practices, and the fact that there is no remuneration for this.³⁴ It is therefore important that patients are given adequate information prior to discharge in order to self-regulate and self-titrate their retainer wear, and to make an informed choice regarding any future costs they may incur in long-term retention wear/replacing retainers.

A study that looked at factors influencing adherence to removable retainer wear found that a lack of follow-up appointments resulted in some patients independently deciding to cease their retainer wear.³⁷ It is, therefore, prudent for all patients to visit their dentist or local specialist orthodontic practice every 1–2 years at the very least, so that their retainers can be assessed. Although more regular retainer review appointments may be the ideal for supporting retainer wear, there is a financial burden associated with this, and each patient must make their own judgement as to the level of support they need.

In any event, all patients should be consented appropriately and informed of the importance of having a long-term retention strategy prior to embarking on a course of treatment. It may also be advisable that the British Orthodontic Society or similar body provides courses on retention management, particularly for GDPs and young dentists/foundation trainees who may have limited experience in managing retainers.

Conclusions

Retention is an integral part of the treatment planning and consent process. We hope this guidance provides some clarity for patients, GDPs and orthodontic specialists on how to manage the requirement for long-term orthodontic retainer wear. The article also provides some guidance and rationale for retention wear and regimens, but these should be modified and individually assessed for each patient and their malocclusion.