ORTHODONTIC FIXED RETAINERS. A SYSTEMATIC REVIEW

Wasserman, Isaac; Ferrer, Karina; Gualdrón, Jesús; Jiménez, Nancy; Mateos, Laura; Wasserman, Isaac; Ferrer, Karina; Gualdrón, Jesús; Jiménez, Nancy; Mateos, Laura

doi:10.17533/udea.rfo.v28n1a8

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Revista Facultad de Odontología Universidad de Antioquia

Print version ISSN 0121-246X

Rev Fac Odontol Univ Antioq vol.28 no.1 Medellín July/Dec. 2016

https://doi.org/10.17533/udea.rfo.v28n1a8

Original article

ORTHODONTIC FIXED RETAINERS. A SYSTEMATIC REVIEW^*

Isaac Wasserman¹

Karina Ferrer²

Jesús Gualdrón²

Nancy Jiménez²

Laura Mateos²

^¹ Orthodontist; Head of the Clínica de Tratamiento Temprano, Graduate Program in Or thodontics, Universidad El Bosque, Bogotá, Colombia

^² DMD, Senior intern at the Universidad El Bosque Or thodontics Graduate School, Bogotá, Colombia

ABSTRACT

Introduction:

the objective of this study was to evaluate the periodontal effects of fixed retainers in the long term.

Methods:

a search in electronic databases (PubMed, Cochrane Library, Science Direct, Embase, ProQuest, Ebsco, Biomed Central, Medline, Lilacs, and Google Scholar) and a manual search with no language restrictions. The inclusion criteria were: randomized clinical trials and meta-analysis, prospective and retrospective studies, studies in humans, clinical and radiographical studies evaluating the periodontium, performed during the 1987-2014 period, up to 10 years of follow-up. Four authors extracted data from the selected studies independently.

Results:

after applying the inclusion criteria, we selected 4 studies in which a total of 405 patients were evaluated. All the studies were longitudinal and retrospective. There was a greater prevalence of gingival recessions, especially in mandibular incisors, which are more vulnerable. There were no significant changes in terms of alveolar bone index or calculus index. The survival rate of fixed retainers was 50% or higher. Due to the heterogeneity of the selected studies, including difference in study population, differences in methods to assess the intervention, and follow-up periods, it was impossible to quantify the variables to perform a meta-analysis.

Conclusions:

the selected studies had a middle level of evidence. The greatest gingival recessions occurred with the use of fixed retainers in a long time; however, there is no alteration of the alveolar bone level. The studies recommend encouraging patients to maintain good oral hygiene. The findings of this review should be cautiously taken due to the resulting level of evidence, and the general recommendation for clinicians is that, in the long run, these retainers appear to be safe to maintain the alignment of mandibular incisors, although more studies with greater scientific rigor are required. There were no conflicts of interest and this study did not have any kind of financial support.

Key words: retainer; braces; periodontal index; retention; orthodontic appliances

RESUMEN.

Introducción:

el objetivo del presente estudio consistió en evaluar los efectos periodontales de los retenedores fijos a largo plazo.

Métodos:

se realizó una búsqueda en bases de datos electrónicas (PubMed, Cochrane Library, Science Direct, Embase, ProQuest, Ebsco, Biomed Central, Medline, Lilacs y Google Scholar) y una búsqueda manual sin restricción de lenguaje. Los criterios de inclusión fueron: ensayos clínicos aleatorizados y metaanálisis, estudios prospectivos y retrospectivos, estudios en humanos, estudios en los que se evaluara clínica y radiográficamente el periodonto, periodo comprendido entre 1987 y 2014, seguimiento hasta 10 años. Cuatro autores extrajeron independientemente los datos de los estudios seleccionados.

Resultados:

después de aplicar los criterios de inclusión, se seleccionaron 4 estudios en los que se evaluaron un total de 405 pacientes. Todos los estudios fueron longitudinales retrospectivos. Se encontró una mayor prevalencia de recesiones gingivales, especialmente de los incisivos mandibulares, que son más vulnerables. No mostraron cambios significativos ni el índice de hueso alveolar ni el índice de cálculo. La tasa de supervivencia de los retenedores fijos fue mayor del 50%. Debido a la heterogeneidad de los estudios seleccionados, entre los cuales se encuentra la diferencia en la población de estudio, diferencias en los métodos para evaluar la intervención y el tiempo de seguimiento, fue imposible cuantificar las variables para realizar un metaanálisis.

Conclusiones:

los estudios seleccionados tuvieron un nivel de evidencia medio. Se presentan mayores recesiones gingivales con el uso de los retenedores fijos a largo plazo; sin embargo, no hay alteración del nivel óseo alveolar. Los estudios recomiendan incentivar al paciente para que mantenga una buena higiene oral. Los resultados de esta revisión se deben tomar con cautela por el nivel de evidencia que arrojaron, y la recomendación general para el clínico es que, a largo plazo, estos retenedores parecen ser seguros para mantener el alineamiento de incisivos mandibulares, aunque se requieren más estudios con mayor rigor científico. No hubo conflictos de intereses y la investigación no contó con ningún tipo de financiamiento.

Palabras clave: retenedor; brackets; índice periodontal; retención; aparatos ortodónticos.

INTRODUCTION

Stabilizing the occlusion achieved by means of orthodontic therapy is one of the main treatment goals.¹⁾⁽²⁾⁽³⁾⁽⁴⁾ Occlusion instability can be divided into two categories: 1. Changes related to growth, maturation and ageing of dentition and occlusion. 2. Changes produced by the orthodontic treatment. Contact and pressure by soft tissues can be another factor influencing stability.¹⁾⁽⁵⁾⁽⁶⁾⁽⁷

The ability to achieve long-term stability and the subsequent understanding of factors affecting stability are an indication for the need to retain the achieved results.¹⁾⁽²⁾⁽⁴⁾⁽⁵⁾⁽⁷⁾⁽⁸⁾⁽⁹In the absence of a retention phase, teeth tend to return to their initial position. To prevent recurrence, it is necessary to perform some form of retention.⁶⁾⁽⁷⁾⁽¹⁰⁾⁽¹¹

Many retention devices are currently used to keep the shape of the arch and to prevent recurrence.¹⁾⁽²⁾⁽⁴⁾⁽⁷⁾⁽⁹⁾⁽¹⁰⁾⁽¹²⁾⁽¹³⁾⁽¹⁴⁾ Designed in 1919, the Hawley plate is the most popular removable retainer.¹⁵⁾ In 1993, Sheridan et al introduced the Essix plates as a modern, aesthetic, comfortable, and inexpensive alternative to traditional retainers.¹⁵⁾⁽¹⁶⁾ Currently, both the Hawley plate and the Essix® plate are the most widely used removable retainers.¹⁵⁾⁽¹⁶⁾ They have a disadvantage though: they need cooperation by the patient.¹⁷⁾⁽¹⁸

With the introduction of the adhesive technique,¹⁹⁾ the lingual retainer has become widely used in recent decades to preserve the changes achieved during orthodontic treatment.⁹⁾⁽¹²⁾⁽²⁰⁾⁽²¹⁾ This consists of a wire of certain length usually bonded from canine to canine on the lingual surface.¹²⁾⁽¹⁹

Since its introduction in 1977, several modifications have been made to the wires used.²²⁾ The first generation consisted of a rounded wire (0.032-0.036 inches) with terminal folds, bonded to the canines only. The second generation did not require terminal folds, since the wire spiral offered good retention; the disadvantage of this retainer is that its diameter (0.032 inches) produces less stability.⁹⁾⁽²²⁾⁽²³

Rigid multi-stranded wires of a bigger diameter (0.032 inches) have been used in the last ten years (0.032 inches) bonded to the canines only, as well as another type of multi-stranded wire usually more flexible and of a smaller diameter (0.017-0.021 inch), bonded on each tooth from canine to canine.¹³⁾⁽¹⁹ The advantage of using multi-stranded wires is that their irregular surface increases mechanical retention with no need of making retentive folds, and the flexibility of the wire allows the physiological movements of teeth.¹⁹⁾⁽²⁴

As an alternative to this type of wire, glass fiber-reinforced resin tapes are used with the disadvantage that they create a very rigid splint that limits the physiological movement of teeth and can cause fissures.¹⁹

Fixed retainers are increasingly used nowadays because they are aesthetic, require less patient cooperation, and provide greater stability in the long term, thus being more predictable.⁹⁾⁽²⁵⁾ However, these retainers make oral hygiene more difficult as the lingual surface becomes more susceptible to the formation of calculus.¹⁷⁾⁽²⁶⁾⁽²⁷⁾ In addition, they may produce gingival recessions, loss of insertion, gingivitis, and the subsequent periodontal destruction.²⁶⁾⁽²⁸⁾⁽²⁹⁾⁽³⁰⁾⁽³¹⁾⁽³²⁾ Tooth decay may also appear on the lingual surfaces adjacent to the retainer.³³

The effect of these retainers on periodontal health is currently debatable.¹⁷⁾⁽²⁶⁾⁽²⁸⁾⁽³³

The goal of this systematic review is to evaluate the periodontal effects of lingual fixed retainers in the long term.

MATERIALS AND METHODS

This systematic review is based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) recommended by the American Journal of Orthodontics and Dentofacial Orthopedics.

The first stage of this systematic review included the identification of elements to be evaluated, creating a PICO chart (Table 1) and formulating the research question: what are the long-term periodontal effects of mandibular fixed retainers?

The inclusion and exclusion criteria used in this study are shown in Table 2.

Table 1 PICO Chart

Table 2 Criteria considered for the studies in this review

Search methods

We conducted a search to identify and select studies in the following databases: PubMed, Cochrane Library, Science Direct, Embase, ProQuest, EBSCO, Biomed Central, Medline, Lilacs, Google Scholar, using the following key words: fixed retainer, orthodontic treatment, periodontal health, retention, fixed appliances (Table 3).

Table 3 Databases and search combinations

Following the first results of the search, we excluded all articles and abstracts that were not related to the topic or did not meet the inclusion criteria. Each search was carried out independently by each researcher; the results were compared reaching to an agreement. If the abstracts did not supply sufficient information, or simply did not exist, full texts were requested to make a final decision.

To locate published material that was not indexed in the available databases, a manual search was conducted in Juan Roa Vásquez library at Universidad El Bosque, reviewing bibliographical references and searching for abstracts or full texts, to find out whether they met the inclusion criteria; this search did not yield any result.

The methodological scoring of the studies is taken from Lagravère and partners,³⁸⁾ with a modification made specifically for this project, which consisted on including studies conducting a follow-up of 0 to 10 years, in order to comply with the inclusion criteria (Table 4). Each selected study received a score (Table 5). The maximum score was 22 points distributed as follows: strong evidence (15-22 points), moderate evidence (8-14 points), and poor evidence (1-7 points). Researchers independently scored each selected article; in case of discrepancies, an agreement was reached by consensus.

Table 4 Methodology scoring chart

Table 5 Methodology classification chart

Low: 1-7; Middle: 8-14; High: 15-22

All selected studies had a score of middle evidence.

RESULTS

Figure 1 describes the flow chart of information obtained through the different phases of a systematic review (PRISMA). Note that the electronic search in the databases yielded 29.526 titles related to the topic, unlike the manual search, which did not return any related title. Of the 29.526 titles, 29.288 were removed for being duplicates, for a total of 238 unique titles.

Figure 1 PRISMA flow chart

The 238 titles were read and 154 were discarded for not being relevant to the topic.

The abstracts of the 84 selected titles were analyzed and 44 articles were discarded for various reasons and by not showing relevance with the subject.

The full texts of the 40 selected articles were analyzed and applied the exclusion and inclusion criteria. Those articles were excluded since they did not evaluate periodontal health but incisor irregularity; in addition, the follow-up period was no longer than two years. In total, only 4 articles met the requirements of this review, and they were evaluated according to the methodology scoring chart. Table 6 shows the characteristics of interest in each selected article.

Table 6 Characteristics of included articles

Calculus Index

A higher calculus index was found by Pandis ³⁴⁾ in the group with long-term retention; on the contrary, Cerny ³⁵⁾ found out that in mandibular lingual surfaces this index scored as very good or good in 80% of the PBR group and 100% of the RR group (p = 0.259). Only a few patients in both groups scored as poor or very poor. The studies by Renkema ³⁶ and Booth ⁽³⁷⁾ did not take this parameter into account.

Gingival index

Of the three studies that evaluated gingival index (Pandis, ³⁴⁾ Cerny, ³⁵ and Booth ³⁷), only one (Booth ³⁷) found statistically significant differences in terms of gingival index scores for maxillary lingual surfaces of both anterior and posterior teeth, with the highest scores in patients with a mandibular retainer in place.

Gingival recessions

The studies by Pandis,³⁴ Cerny,³⁵⁾ and Renkema ³⁶⁾ evaluated the presence of gingival recessions with the use of fixed retainers. The study by Pandis ³⁴⁾ found a high prevalence of gingival recessions in the group using retainers for a long time. A similar result was found in the study by Renkema, ³⁶⁾ which showed a relation between orthodontic treatment and/or the retention phase with gingival recessions over time. They found that the average number of recessions in treated cases is estimated as 142% higher than the control groups, showing an association between fixed retainers and gingival recessions, being the lower incisors teeth more vulnerable. Contrary to these two studies, the study by Cerny ³⁵⁾ found out that none of the classifications of the Dental Health Index significantly differed between the two groups, including gingival recessions, with a tendency to show classifications with lower percentages in the group with fixed retainers, but these differences were not statistically significant.

Bone level

Two of the studies (Pandis ³⁴ and Cerny (³⁵⁾) found out that, in a follow-up period of 9 to 17 years, bone level with the use of fixed retainers showed no significant differences in comparing short- and long-term removable retainers. In the study by Cerny, ³⁵⁾ the index of maxillary alveolar bone was rated as very good or good in 85% of the PBR group and 90% of the RR group, and in the mandible, it was very good or good in 100% of the PBR group and 90% of the RR group.

Age, gender and Angle’s molar relation

Although the study by Pandis ³⁴⁾ took age into account to observe homogeneity of the groups, only the study by Renkema ³⁶⁾ evaluated gingival recessions at different ages, finding out that age seems to greatly influence the development of gingival recessions since these increased at different measurement times. Regarding gender, none of the studies evaluated its relationship with lingual retainers; only the study by Pandis ³⁴⁾ presented it at baseline. Angle’s classification was considered in the study by Renkema, ³⁶⁾ finding out no differences among classes I, II, and III malocclusions and gingival recessions in the treated group.

Survival of fixed retainers

The survival of fixed retainers was evaluated in two studies (Cerny ³⁵⁾ and Booth ³⁷). In the study by Cerny, ³⁵⁾ 21 of the 242 compound adhesions and 5 of the 55 wire retainers had breaks during 15 years, for a total fractured PBR rate of 3,15% per year and a wire unit/accession fracture rate of 0,58% per year. There were 81% of fractures by adhesion failure and 19% by wire fractures. Of the adhesion fractures, 43% were related to the patient biting something hard, while the causes of the remaining 57% were unknown. Booth ³⁷⁾ found out that 45 patients who still had a retainer in place 20 years later, 28 (62%) had no breaks in that period, 18% required one repair, and 20% required more than one repair.

DISCUSSION

The present systematic review focused on determining the periodontal effects of fixed retainers in the long term during the retention phase following orthodontic treatment. All the articles finally selected were of a retrospective type and showed moderate evidence.

None of the studies was randomized or calculated sample size. Only one of the four articles presented similar characteristics at baseline. Only one study ³⁵⁾ reported blind examiner; none of the others included blinding in measurements or statistics. Two of the studies ³⁴⁾⁽³⁷⁾ failed to report reliability of measurements. Only one of the studies reported error.³⁵⁾ On the other hand, the statistical analysis was appropriate in all the studies; however, only one ³⁶⁾ reported having carried out combined analysis of subgroups. Confounders were not considered in any of the studies and the p value was described by all, but only one ³⁶⁾ established confidence intervals.

Previous studies have evaluated the periodontal effects of retainers in different time periods. Levin et al evaluated the association of orthodontic treatment and fixed retainers with gingival health. Periodontal parameters, plaque index, gingival index, gingival recession, and depth and bleeding on probing were measured on six sites per tooth. They concluded that fixed retainers are associated with the increase in gingival recessions, plaque retention and bleeding on probing. Therefore, they recommended meticulous oral hygiene and regular visits to the dentist for monitoring.²⁹

On the other hand, Artun et al analyzed the tendency to the formation of plaque and dental calculus on the wire of different types of fixed orthodontic retainers from canine to canine and one removable retainer. The 49 patients included in the study were sorted out into 4 groups; there were 11 patients in the group of plain fixed retainers cemented in canines only, 13 patients in the group of fixed retainers made of multi-stranded wire cemented in canines only, 11 patients in the group of retainers made of multi-stranded wire but cemented in all teeth from canine to canine, and 14 patients in the group of removable retainers. Each group was evaluated 3 years after having placed the retainers, to determine the accumulation of plaque and calculus and gingival inflammation along the gingival margin of incisors and mandibular canines, based on Löe’s plaque index and gingival index, as well as Ramfjord’s calculus index. The authors concluded that the presence of a fixed retainer doesn’t seem to have any negative periodontal effect, if patients perform satisfactory hygiene along the gingival margin.²¹

In a prospective study, Al-Nimri et al evaluated gingival health and the accumulation of plaque in lingual retainers made of multi-stranded wire cemented to all anterior mandibular teeth, comparing them with retainers made in round wire and cemented in canines only. The evaluated parameters were: index of oral hygiene, plaque index, and gingival index in lower anterior teeth. They concluded that there were no significant differences in the gingival condition of lower anterior teeth with the fixed multi-stranded wire nor with the fixed retainer made of round wire.³⁰⁾ The aforementioned studies were not included in this research project because they did not meet the follow-up time criterion (0 to 10 years).

This systematic review included four studies evaluating the periodontal effects of fixed retainers in a period of ten years or less, with different measurement variables.

The results obtained in terms of calculus index are not conclusive because this parameter was evaluated in two of the studies which differ between them, since Pandis et al ³⁴⁾ claim that there was a greater calculus accumulation in patients with fixed lingual retainers evaluated in a long period, while Cerny et al ³⁵⁾ found satisfactory results in 80% of the evaluated cases with fixed retainer and in 100% of cases with removable retainers. The same happens with gingival index, which was evaluated in three of the four studies, but only Booth et al ³⁷⁾ found statistically significant differences in the maxillary lingual surfaces, while Pandis ³⁴⁾ and Cerny ³⁵⁾ found no differences.

In terms of gingival recessions, Pandis ³⁴⁾ and Renkema ³⁶⁾ found association between the presence of a lingual fixed retainer and the development of gingival recessions; however, Cerny ³⁵⁾ found no significant difference between the studied groups. On the other hand, Renkema ³⁷ found a relation between patient's age and the appearance of gingival recessions.

The results of the two studies ³⁴⁾⁽³⁵⁾ that evaluated bone level changes are in agreement, stating that there are no significant differences between the groups observed in the short and long term, nor among the groups using fixed retainer and removable retainer.

Two studies evaluated the incisive irregularity index, finding out slight changes in this sense. Observing patients with 15 years of retention, Cerny found an index of irregularity of 0.26 mm in patients with retainers fixed. Booth’s results agree with Cerny’s, finding out that only 1 of 45 patients showed an index of irregularity greater than 2 mm.³⁵⁾⁽³⁷⁾ No article reports differences in maxillary and mandibular retainers.

Since the information found is limited, and given that most results are not conclusive, no absolute conclusions can be drawn; it is therefore recommended to conduct more research and randomized clinical trials, in order to determine the periodontal effects of lingual fixed retainers in the long term. However, is important to highlight that most authors refer to the importance of encouraging patients to keep good oral hygiene to avoid later periodontal complications.

CONCLUSIONS

1. There is association between gingival recessions and fixed retainers in the long term; however, there is no alteration of the alveolar bone level.

2. The results should be cautiously taken due to the middle level of evidence found.

3. The recommendation for clinicians is that these retainers seem to be safe in the long term, provided that patients are instructed in good oral health habits in order to reduce the accumulation of plaque and calculus.

CONFLICT OF INTEREST

The authors declare that they have no conflict of interest.

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¹Wasserman I, Ferrer K, Gualdrón J, Jiménez N, Mateos L. Orthodontic fixed retainers. A systematic review. Rev Fac Odontol Univ -Antioq 2016; 28 (1): 139-157. DOI: http: //dx.doi.org/10.17533/udea.rfo.v28n1a8

Received: December 02, 2014; Accepted: August 30, 2016

CORRESPONDENCIA Isaac Wasserman, Universidad El Bosque, (+57) 314 295 7500, wassermanisaac@unbosque.edu.co, Bogotá, Colombia

This is an open-access article distributed under the terms of the Creative Commons Attribution License