The prescription of lifelong Orthodontic retainers seems to be an inevitable requirement to contain post-orthodontic treatment relapse or change. Various factors contribute to relapse, including time needed to stabilise periodontal supragingival and transseptal fibres, occlusal forces, active growth to name a few. Currently, mechanical retention in the form of removable or fixed retainers is widely used to counter these changes. Orthodontic retainers have limitations, removable retainers require consistent patient compliance and fixed retainers can have mechanical failures amongst other disadvantages. Efforts have been made to provide adjuncts or a replacement to these mechanical forms of retention, for example: Frenectomy, Supracrestal Circumferential Fiberotomy (CSF), Interproximal proximal reduction (IPR), pharmacological agents, mechanical vibrations, Alveolar Corticotomy and Low-level Laser have been studied for effectiveness.
The aim of this review was to evaluate efficacy of adjuncts or alternatives to mechanical retention in preserving post orthodontic treatment outcomes.
The protocol was registered on PROSPERO. Database search included Medline, Embase, Web of Science, Cochrane Central Register of Controlled Trials, LILACS and Bireme without language restrictions. Unpublished literature was accessed via ClinicalTrials.gov, National Research Register, Proquest Dissertation and Abstracts and Thesis database. Two authors independently made the search, collected the data, conducted risk of bias assessment with disagreements assessed by a third author. Eligibility criteria included Randomised Control Trials (RCTs) as well as Non-Randomised Trials(NRCT). Selection was based on patients who completed fixed appliance or aligner orthodontic treatment and were in the retention phase. Trials with patients who received surgical or non-surgical interventions with or without use or retainers were included. Patients who received no retainers with no alternatives were included. Comparison was made with patients who received only fixed or removable retainers.
Primary outcomes involved stability (contact point displacement measure with Little’s Irregularity Index, space reopening, rotations, arch length, width changes, relapse of overjet/overbite). Secondary outcomes involved periodontal effect, dental sensitivity, dental caries, cost effectiveness, patient-reported outcomes. Risk of bias was assessed using The Cochrane Risk of Bias Tool and Risk of Bias in Nonrandomized Studies of Interventions (ROBINS-1). Mean difference (2mm change being clinically significant) and standard deviation were used to describe findings. Assessment of clinical and statistical heterogeneity indicated moderate to high heterogeneity precluding meta-analysis. Certainty of the evidence was appraised using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system. The weighed treatment effects of the intervention were calculated with Exploratory sensitivity analysis.
- 7 trials were included in the study (5 RCTs, 2 NRCT).
- High risk of bias was noted in 5 trials and unclear bias reported in 2 studies.
- Heterogeneity and the low number of studies could not enable a meta-analysis.
- Stability outcomes were based on Little’s Irregularity Index and intercanine width. Rotations were not specifically evaluated.
- Periodontal outcomes were reported in one study.
- Two studies assessed low-level laser with removable retainer wear.
- One study assessed IPR on mandibular labial segment stability and cost effectiveness.
- There were no reports on dental sensitivity, caries or patient reported outcomes in any of the studies.
- Some evidence supported the use of CSF to improve stability (better preservation of labial segment alignment) with CSF as an adjunct compared to isolated use of retainers. CSF resulted in less increase in the mandibular Little’s Irregularity Index (mean difference, -2.30mm; confidence interval, -2.86 to -1.74). Very low level of evidence and methodological concerns were noticed in the studies. The apparent benefit of the surgical adjunct also seemed to reduce over time as relapse became more evident.
- Improved stability was noted in one study of IPR adjunct compared to removable retainers alone. Post treatment IPR when compared to a fixed retainer or a prefabricated positioner was shown to be more cost-effective as well. This apparent benefit should be balanced by the limitations posed by finite availability of enamel.
- One study noted better stability at 1-year follow up for Low-level Laser intervention. Although, one study mentioned no difference in diastema space re-opening with the use of low-level laser as an adjunct to Hawley’s retainer. Factors such as extent of pre-treatment diastema, family history, subsequent interventions with frenectomies may have a confounding effect on the results.
The authors concluded: –
The interventions assessed in most of the included studies were adjunctive to mechanical retention rather than isolated alternatives. A very low level of evidence was found. Currently, there is a lack of high-quality evidence to support the prescription of adjunctive or alternative procedures. Furthermore, the acceptability of these approaches to patients was overlooked and remains unclear.
A good range of databases was searched and this review suggests some promise to the use of adjuncts or alternatives to mechanical retention. The existing evidence though does not recommend reducing the use of mechanical retention. CSF has shown possible improvement in stability outcomes but requires further studies to determine its benefit.
Extensive limitations in the review were noticed. The number of trials included was very low with a very low level of evidence, precluding a meta-analysis. Publication bias could not be assessed due to the limited number of included studies. All of this in turn has highlighted the need for further prospective studies. Patient factors like compliance, acceptability and pain were not taken into consideration in most studies. Most studies included comparison with removable retainers but not many with fixed retainers despite their extensive clinical use. Follow up periods were too short to accurately depict the long-term advantages of the interventions implemented. CSF is prescribed to prevent rotational relapse, but the studies failed to record reciprocal rotations with the Little’s Irregularity Index in the included studies.
In trials involving long term reviews, it’s frequent to see patients leaving a trial before it’s completion. The authors advise that further studies account for this dropout in the initial study design and maintain review appointments with remote software to maintain retention. Midline diastema correction quite commonly involves frenectomies. For a procedure done so routinely the evidence available to support it is very less. The authors highlight this fact for future prospective studies. High-quality prospective research with a focus on the predictability and acceptability of these approaches are recommended.
Al-Moghrabi D, Algharbi M, Arqub SA, Alkadhimi A, Fleming PS. The effectiveness of adjuncts or alternatives to the use of orthodontic retainers in preserving posttreatment outcomes: A systematic review. Am J Orthod Dentofacial Orthop. 2023 Jan;163(1):9-21.e3. doi: 10.1016/j.ajodo.2022.08.022. Epub 2022 Nov 3. PMID: 36335023.
Dental Elf – Orthodontic retainer blogs
By Hondur – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=35232511