The Impact of Orthodontic Retainers on Gingival Recession: A Best-Evidence Review

In this study, the authors attempt to address the following clinical question: "In orthodontically treated patients, how does the type of retainer affect the prevalence of gingival recession on mandibular anterior teeth?"

Two systemically healthy patients, a 37-year-old Caucasian male (patient A) and a 33-year-old Caucasian female (patient B), presented to the University of Alabama at Birmingham School of Dentistry clinics in January 2020 for periodontal examinations and prophylaxis visits. Both patients' dental history questionnaires revealed 2-year orthodontic treatments with fixed appliances during adolescence followed by retention with fixed bonded retainers from mandibular canine to canine. The patients reported a history of dental prophylaxis visits on a yearly basis. In patient A, who reported difficulty in maintaining oral hygiene in the retainer area, mild plaque and moderate calculus accumulation was noted on lingual and interproximal aspects of the mandibular anterior teeth. In addition, slight gingival recession was detected on the lingual aspect of his mandibular incisors. In contrast, patient B displayed less plaque and calculus accumulation and no recession despite having a fixed retainer bonded on every mandibular incisor and canine. Facial and lingual views of both patients' mandibular anterior teeth at initial presentation are shown in Figure 1 through Figure 4.

Orthodontic treatment aims to achieve stable occlusion and dentofacial esthetics. Stability is critical, as relapse is an unpredictable yet common occurrence after orthodontic therapy. Maintaining the mandibular intercanine distance as well as proper correction of the malocclusion, including incisor alignment and angulation, are necessary elements of long-term stability of orthodontic treatment.¹ Although relapse does not necessarily denote a reversal to the initial malocclusion, it is represented by any unwanted movement of the teeth after treatment and is manifested by anterior crowding. In untreated as well as treated dentitions, a decrease in mandibular arch length and arch width is observed in the second and third decades of life, despite the completion of active growth.² Long-term post-orthodontic follow-up, spanning 10 to 20 years, has revealed that less than 30% of cases showed stability in the anterior mandibular segment with 20% of those cases showing likelihood for crowding years after retainer removal.³ Retention also maintains the stability of the occlusion by counteracting the tension of the interdental and dentogingival fibers, which contributes to relapse.⁴ Therefore, the retention phase is critical after active treatment to improve the stability of the long-term success of orthodontic therapy, with some authors recommending its use for life.^1-3 Ideal retention will help maintain the occlusion and periodontal health of the patient.

The most common types of retainers used for retention in the mandibular arch are fixed bonded retainers from canine to canine, removable vacuum-formed retainers covering all teeth, or mandibular Hawley retainers. Each appliance has its own advantages and disadvantages. While removable retainers in the maxilla and mandible are typically used for retention of all teeth in the arch, fixed retainers are most commonly placed on the six mandibular anterior teeth. The presence of retainers may affect gingival tissue health when placed in close proximity of the gingival tissue.⁵ Removable retainers allow easier maintenance of oral hygiene but require greater patient compliance to avoid relapse. In contrast, fixed retainers decrease the chance of relapse and rely far less on patient compliance. However, they are technique sensitive, require more chairside time, and aid in plaque accumulation, because they act as an obstacle against the daily removal of plaque.⁶

The purpose of this article is to evaluate available evidence regarding the effects of different types of orthodontic retention appliances on gingival tissue, specifically gingival recession, at the mandibular anterior teeth. Understanding the influence of retainer types on the occurrence or progression of gingival recession may help establish retention protocols that are conducive to maintenance of periodontal health as well as orthodontic outcomes.

To obtain literature essential to the development of this best evidence topic, a search string was developed for the PubMed database and then modified for use in the remaining databases searched: Scopus, Cochrane Library, Embase, and Dentistry & Oral Sciences Source. All database searches took place in February 2020. The PubMed search string follows: ("Orthodontic Retainers"[Mesh] OR retain*[Text Word] OR "Orthodontic Appliances"[Mesh] OR "vacuum retainer"[Text Word] OR "vacuum retainers"[Text Word] OR "vacuum formed retainer"[Text Word] OR "vacuum formed retainers"[Text Word] OR "vacuum-formed retainer"[Text Word] OR "vacuum-formed retainers"[Text Word] OR "hawley retainer"[Text Word] OR "hawley retainers"[Text Word]) AND ("Gingival Recession"[Mesh] OR "gingival recession"[Text Word] OR "receding gums"[Text Word] OR "receded gums"[Text Word] OR "gum recession"[Text Word] OR "receding gum"[Text Word] OR "receded gum"[Text Word]) AND ("Cuspid"[Mesh] OR cuspid*[Text Word] OR "eye tooth"[Text Word] OR eyetooth[Text Word] OR "eye-tooth"[Text Word] OR "eye teeth"[Text Word] OR eyeteeth[Text Word] OR "eye teeth"[Text Word] OR "canine tooth"[Text Word] OR "canine teeth"[Text Word] OR "Incisor"[Mesh] OR incisor*[Text Word]) AND (english[Filter]).

Forty abstracts and 13 full articles were reviewed. Forty-two papers were eliminated because their findings did not specifically discuss the effect of retainers on marginal gingival recession in mandibular anterior teeth. Eleven publications are reviewed in this article and summarized in Table 1 (click here to view Table 1).^5,7-16

Retention is the final component of orthodontic treatment and is vital in ensuring the long-term maintenance and stability of the esthetic and functional results.^1-3 Common types of retention methods include fixed bonded retainers and removable retainer appliances. A recent systematic review concluded that there is a lack of high-quality evidence to recommend the use of one type of orthodontic retainer (fixed or removable) with regard to effect on periodontal health.¹⁷

Gingival recession results in apical migration of the gingival tissue that leads to exposure of the root apical to the cementoenamel junction.¹⁸ Recession increases with age and equally affects individuals with high and low levels of oral hygiene.¹⁹ Recession can occur labially or lingually, is unesthetic, and can potentially lead to dentin hypersensitivity, root caries, soft-tissue discomfort, and a greater susceptibility to inflammatory insult.²⁰ These clinically adverse conditions highlight the importance of having a proper understanding of the effects that different types of retainers can have on the prevalence of recession in the gingival tissue.

Predisposing factors that have been implicated in the development or progression of gingival recession include periodontitis, periodontal therapy, thin periodontal phenotype,^21,22 improper toothbrushing through increased duration, frequency, force, or brush bristle size,^23,24 presence of intracrevicular restorative margins especially in the absence of keratinized gingiva,²¹ orthodontic treatment,^25,26 and shallow vestibular depth and frenum position that interfere with proper plaque control.²⁷ Several of these factors are considered to have a low level of evidence.²⁸

Numerous publications have investigated the overall periodontal effects retainers have on periodontal health and plaque and calculus accumulation on the gingival tissue.^{5,7,9-13,15,29} In a recent systematic review that underscored the lack of high-level evidence, orthodontic fixed retainers were considered compatible with periodontal health or at least not related to severe detrimental effects on the periodontium.¹⁶

The influence of orthodontics on gingival recession in the anterior mandible has been largely evaluated through the effect of tooth movement, in particular incisor proclination. There is weak evidence and conflicting information available, as some studies report a higher incidence of recession with proclined incisors,²⁶ whereas others fail to demonstrate such an association.^30,31 Nevertheless, these studies agree that the recession observed over time is likely related to the aging of patients, similar to reports from epidemiological studies.³²

This article highlights studies (summarized in Table 1 [click here to view Table 1]) that specifically evaluated the effects of orthodontic retainers on the initiation or progression of gingival recession. The included studies showed heterogenicity in their sample and study design. Most studies compared orthodontically treated groups using different types of retainers.^{8,11,12,15,33} Two studies compared orthodontically treated patients who were prescribed retainers to non-orthodontically treated patients.^5,10 Only one study compared orthodontically treated patients with retainers to orthodontically treated patients without retainers and used non-orthodontically treated patients as a control group.¹³ The evaluation methods of gingival recession also differed between studies. While three studies dichotomously reported gingival recession as merely "present" or not,^10,11,13 seven of the studies measured the amount of recession present.^{5,7-9,12,15,29} Methods of recession measurement varied from direct clinical measurements to indirect cast measurements to evaluation of intraoral photographs. Only three studies compared fixed retainers with no retainers,^5,10,13 and four studies compared different types of fixed retainers to each other.^8,9,11,12 Three studies compared fixed retainers with removable retainers.^6,7,12

Fixed retainers, which are commonly used to alleviate the need for patient compliance, have been found to have no significant effect on the prevalence of recession regardless of type of wire and bonding technique.^7,12,15 Furthermore, the length of retainer use can also be a confounding factor. There is no evidence that has determined an ideal retention duration; however, there is general consensus that retention is recommended for life. One study comparing the prevalence of recession in patients with long-term and short-term use of fixed retainers noted an increase in gingival recession in the long-term group.⁹ However, these recessions were found mostly buccally, thus weakening the association of the lingually placed fixed retainer on the occurrence of gingival recession.

Despite the general consensus, a study that compared patients with fixed retainers to patients who did not undergo orthodontic treatment had contradictory results stating that the fixed retainer significantly impacted the likelihood of recession by increasing that risk by a 4.8-fold.¹⁰ The recessions in that study were labial, and the authors noted that it was unclear whether the recessions occurred as a result of orthodontic treatment or presence of the fixed retainer.

It is noteworthy that only one reviewed study reported on the gingival-incisal position of the retainer.⁵ The study showed that a more gingival position of the retainer was associated with greater recession compared with a more incisal position, although the difference was not statistically significant.⁵ It could be suggested that the closer the retainer is bonded to the gingival tissues, the greater negative influence it could impose on periodontal health.

In summary, the reviewed studies^5,7-16 either did not demonstrate an association between orthodontic retainers and gingival recession or reported that the resulting recession defects were minimal when an association was shown. These studies are mostly retrospective and the majority do not specifically report on lingual recession. An important consideration is that recession could be a late finding following the placement of a retainer; therefore, it may be incipient or absent in short-term evaluations. Prospective studies aimed at specifically addressing the role that properly positioned fixed retainers may have on gingival recession are needed before a definitive conclusion can be generalized with regard to recommended retention protocols.

Within the limitations of the reviewed studies, it is unclear whether fixed or removable orthodontic retainers affect the initiation or progression of marginal gingival recession. Factors such as duration of retainer use, number of bonded teeth, and position of fixed retainers relative to their proximity to gingival tissues are not fully elucidated but may have influencing roles on gingival recession. The use of retainers is dependent on the patient's malocclusion and should be based on orthodontic indications to maintain a stable dental arch form, esthetics, and occlusion. Effective oral hygiene and follow-up regimens remain the gold standard in maintaining periodontal health and preventing gingival recession.

The authors had no conflicts of interest to report.

Nada M. Souccar, DDS, MS
Associate Professor, Department of Orthodontics, University of Alabama at Birmingham School of Dentistry, Birmingham, Alabama

Rawan Oueis, DDS
Resident, Department of Orthodontics, University of Alabama at Birmingham School of Dentistry, Birmingham, Alabama

John Paul Mussleman, Jr., MLIS
Associate Professor, Lister Hill Library of the Health Sciences, University of Alabama at Birmingham School of Dentistry, Birmingham, Alabama

Nicolaas C. Geurs, DDS, MS
Weatherford-Palcanis Endowed Professor and Chair, Department of Periodontology, University of Alabama at Birmingham School of Dentistry, Birmingham, Alabama

Ramzi V. Abou-Arraj, DDS, MS
Associate Professor, Director, Graduate Periodontology Clinic, Assistant Director, Advanced Education in Periodontology,Department of Periodontology, University of Alabama at Birmingham School of Dentistry, Birmingham, Alabama

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