Which is better: Essix retainers or fixed retainers?

Introduction

There are different retention strategies to maintain the position of the teeth in the maxilla. The strategies commonly include a bonded retainer between the maxillary canines (6, 7). Also removable vacuum-formed retainers (VFRs) are widely used, and VFRs have been reported to produce stability as good as that produced by fixed retainers (8). Each strategy has both advantages and disadvantages. Bonded retainers have the advantage of being independent of the compliance of the patients, but are at risk for coming unattached or being fractured (8, 9). A reduced extension of the retainer, to include only the maxillary incisors, may result in fewer complications compared with a retainer that also includes the canines. In addition, the maxillary canines seem to be more stable after treatment than the incisors, and thus, do not need to be included in the retainer (7, 10, 11). Nevertheless, the use of bonded retainers, regardless of design, makes cleaning in approximal areas more difficult, which might increase the risk for accumulation of plaque and development of gingivitis and caries (12, 13). Thus, the use of a removable retainer may facilitate the maintenance of good oral hygiene compared with the use of a bonded retainer. But a shortcoming with a removable retainer in the long run is dependency on the patient’s compliance, and thus there is a risk of relapse in cases of non-compliance (14, 15).

Cost analysis of two types of fixed maxillary retainers and a removable vacuum-formed maxillary retainer: a randomized controlled trial. © The Author(s) 2022. Published by Oxford University Press on behalf of the European Orthodontic Society. Creative Commons Attribution 4.0 International (https://creativecommons.org/licenses/by/4.0/).

Introduction and background

Retainers are usually worn after active orthodontic treatment to preserve the arch dimension and the alignment of the teeth. They may also facilitate post-treatment settling [13]. Hawley-type retainers (HR) and Begg's wrap-around retainer (BGR) allow vertical settling as they hold only the lingual and buccal surfaces of the teeth [14,15]. Fixed or bonded retainers allow occlusal settling which can be attributed to eruption and vertical mobility of posterior teeth during retention [16]. Removable vacuum-formed retainers (VFRs) cover the occluding surfaces of teeth, thereby exerting a bite-block effect [10]. They are well accepted by patients and are better than other removable retainers in terms of ease of swallowing fluids and esthetics [17]. However, their occlusal coverage can impede vertical settling [18]. Even though a few clinical trials [3,11,12,18] have assessed the occlusal contact changes with VFRs or Essix retainers at the end of retention, there are no systematic reviews addressing the same. To thoroughly assess the literature that is now available and report on it, the present review was conducted. The current review aims to compare VFRs to other retainers and critically evaluate the research that is currently available on changes in OSA, OFD, and the number of occlusal contacts (NOC) during the retention period.

Occlusal Contact Surface Changes and Occlusal Force Distribution Between Vacuum-Formed Retainers and Other Retainers: A Systematic Review. Copyright © 2023, Singh et al.. Creative Commons Attribution 4.0 International (https://creativecommons.org/licenses/by/4.0/).

Introduction

A recent Cochrane review exposed a lack of high-quality evidence to favor one method of retention over another in terms of stability [3]. Given this absence of definitive evidence, retainer selection is often based on individual preference. This is evidenced by marked geographical variation with maxillary Hawley or vacuum-formed retainers and mandibular fixed lingual retainers with full-time wear of removable retainers most popular in the USA [4, 5]. In Australia and New Zealand, mandibular fixed and maxillary vacuum-formed retainers are shown to be the most prevalent combination [6], while a preference for the use of fixed retainers in both arches has been shown in the Netherlands [7]. The duration of wear of orthodontic retainers has long been a dilemma in orthodontics. However, there is now widespread acceptance of the necessity for indefinite retention to minimize both relapse and maturational changes [5, 8]. Prolonged retention may pose increased risk to the periodontium and dental hard tissues; it is therefore important to investigate the implications of the long-term use of fixed and removable retainers on the supporting tissues [3, 9, 10].

The effects of fixed and removable orthodontic retainers: a systematic review. © The Author(s). 2016. Creative Commons Attribution 4.0 International (https://creativecommons.org/licenses/by/4.0/).

Discussion

While the primary focus of this review was to compare the effectiveness of retainer types, it was also possible to generate epidemiological data on the risk of failure of fixed retainers based on the primary studies. Failure risk of 0.29 was found for fixed wires bonded to the six anterior teeth and approximately one-quarter of retainers bonded to mandibular canines only, based on observation periods of 6 months to 3 years. This data highlights that the risk of failure is considerable and that fixed retention does not guarantee prolonged stability. Similar findings have been observed in observational studies [2]. The onus on realistic treatment planning with due consideration for placement of teeth into a zone of relative stability therefore remains [37].

The effects of fixed and removable orthodontic retainers: a systematic review. © The Author(s). 2016. Creative Commons Attribution 4.0 International (https://creativecommons.org/licenses/by/4.0/).

Abstract

BACKGROUND: Evidence concerning the most appropriate retention strategy after orthodontic treatment is still inconclusive. OBJECTIVE: This trial compares the retentive capacity of vacuum-formed Essix C-retainers (VFR) and bonded cuspid-to-cuspid retainers (CTC) in the mandible 6 and 18 months after orthodontic treatment. TRIAL DESIGN: A single-centre two-arm parallel-group randomized controlled trial. METHODS: This study included 104 adolescent patients, computer-generated randomized with sequentially numbered, opaque, and sealed envelopes into two groups and stratified by gender (52 females and 52 males). The patients were treated with fixed appliances with and without tooth extractions in both jaws and were ready for debond. In the intervention arm, patients received a VFR (n = 52); in the active comparator arm, patients received a CTC (n = 52). Dental casts were obtained at debond (T1), after 6 months (T2), and after 18 months (T3). The casts were digitized. The retentive capacity was evaluated on digital three-dimensional models using Little's Irregularity Index (LII), overbite, overjet, arch length, and intermolar and intercanine width. RESULTS: Baseline values were similar for both groups. Statistically significant increases were noted in LII and overbite, mainly between T1 and T2, but also between T1 and T3 in the VFR group (LII = 0.52 mm, P < 0.001, overbite = 0.51 mm, P < 0.001) and in the CTC group (LII = 0.45 mm P < 0.001, overbite = 0.36 mm, P < 0.001). There were no significant differences between groups. Overjet showed small variations during the observation periods but was overall stable within and between groups after 18 months. Arch length decreased slightly in both groups after 6 and 18 months. Intermolar and intercanine widths remained stable after debond. LIMITATIONS: Patients, operator, and outcome assessor could not be blinded due to the study design. CONCLUSIONS: VFR and CTC have the same retention capacity in the mandible after 6 and 18 months. Relapse mainly occurs during the first 6 months of retention, but the post-treatment changes are generally small. Shorter VFRs in the mandible do not cause negative vertical effects. Part-time wear regimen is not associated with increased relapse. TRIAL REGISTRATION: NCT03070444.