Retention procedures for stabilising tooth position after treatment with orthodontic braces.

BACKGROUND: Without a phase of retention after successful orthodontic treatment, teeth tend to 'relapse', that is, to return to their initial position. Retention is achieved by fitting fixed or removable retainers to provide stability to the teeth while avoiding damage to teeth and gums. Removable retainers can be worn full- or part-time. Retainers vary in shape, material, and the way they are made. Adjunctive procedures are sometimes used to try to improve retention, for example, reshaping teeth where they contact ('interproximal reduction'), or cutting fibres around teeth ('percision'). This review is an update of one originally published in 2004 and last updated in 2016. OBJECTIVES: To evaluate the effects of different retainers and retention strategies used to stabilise tooth position after orthodontic braces. SEARCH METHODS: An information specialist searched Cochrane Oral Health Trials Register, CENTRAL, MEDLINE, Embase and OpenGrey up to 27 April 2022 and used additional search methods to identify published, unpublished and ongoing studies.  SELECTION CRITERIA: Randomised controlled trials (RCTs) involving children and adults who had retainers fitted or adjunctive procedures undertaken to prevent relapse following orthodontic treatment with braces. We excluded studies with aligners. DATA COLLECTION AND ANALYSIS: Two review authors independently screened eligible studies, assessed risk of bias and extracted data. Outcomes were stability or relapse of tooth position, retainer failure (i.e. broken, detached, worn out, ill-fitting or lost), adverse effects on teeth and gums (i.e. plaque, gingival and bleeding indices), and participant satisfaction. We calculated mean differences (MD) for continuous data, risk ratios (RR) or risk differences (RD) for dichotomous data, and hazard ratios (HR) for survival data, all with 95% confidence intervals (CI). We conducted meta-analyses when similar studies reported outcomes at the same time point; otherwise results were reported as mean ranges. We prioritised reporting of Little's Irregularity Index (crookedness of anterior teeth) to measure relapse, judging the minimum important difference to be 1 mm. MAIN RESULTS: We included 47 studies, with 4377 participants. The studies evaluated: removable versus fixed retainers (8 studies); different types of fixed retainers (22 studies) or bonding materials (3 studies); and different types of removable retainers (16 studies). Four studies evaluated more than one comparison. We judged 28 studies to have high risk of bias, 11 to have low risk, and eight studies as unclear.  We focused on 12-month follow-up.  The evidence is low or very low certainty. Most comparisons and outcomes were evaluated in only one study at high risk of bias, and most studies measured outcomes after less than a year. Removable versus fixed retainers Removable (part-time) versus fixed   One study reported that participants wearing clear plastic retainers part-time in the lower arch had more relapse than participants with multistrand fixed retainers, but the amount was not clinically significant (Little's Irregularity Index (LII) MD 0.92 mm, 95% CI 0.23 to 1.61; 56 participants). Removable retainers were more likely to cause discomfort (RR 12.22; 95% CI 1.69 to 88.52; 57 participants), but were associated with less retainer failure (RR 0.44, 95% CI 0.20 to 0.98; 57 participants) and better periodontal health (Gingival Index (GI) MD -0.34, 95% CI -0.66 to -0.02; 59 participants). Removable (full-time) versus fixed   One study reported that removable clear plastic retainers worn full-time in the lower arch did not provide any clinically significant benefit for tooth stability over fixed retainers (LII MD 0.60 mm, 95% CI 0.17 to 1.03; 84 participants). Participants with clear plastic retainers had better periodontal health (gingival bleeding RR 0.53, 95% CI 0.31 to 0.88; 84 participants), but higher risk of retainer failure (RR 3.42, 95% CI 1.38 to 8.47; 77 participants). The study found no difference between retainers for caries.  Different types of fixed retainers Computer-aided design/computer-aided manufacturing (CAD/CAM) nitinol versus conventional/analogue multistrand One study reported that CAD/CAM nitinol fixed retainers were better for tooth stability, but the difference was not clinically significant (LII MD -0.46 mm, 95% CI -0.72 to -0.21; 66 participants). There was no evidence of a difference between retainers for periodontal health (GI MD 0.00, 95% CI -0.16 to 0.16; 2 studies, 107 participants), or retainer survival (RR 1.29, 95% CI 0.67 to 2.49; 1 study, 41 participants). Fibre-reinforced composite versus conventional multistrand/spiral wire  One study reported that fibre-reinforced composite fixed retainers provided better stability than multistrand retainers, but this was not of a clinically significant amount (LII MD -0.70 mm, 95% CI -1.17 to -0.23; 52 participants). The fibre-reinforced retainers had better patient satisfaction with aesthetics (MD 1.49 cm on a visual analogue scale, 95% CI 0.76 to 2.22; 1 study, 32 participants), and similar retainer survival rates (RR 1.01, 95% CI 0.84 to 1.21; 7 studies; 1337 participants) at 12 months. However, failures occurred earlier (MD -1.48 months, 95% CI -1.88 to -1.08; 2 studies, 103 participants; 24-month follow-up) and more gingival inflammation at six months, though bleeding on probing (BoP) was similar (GI MD 0.59, 95% CI 0.13 to 1.05; BoP MD 0.33, 95% CI -0.13 to 0.79; 1 study, 40 participants). Different types of removable retainers Clear plastic versus Hawley When worn in the lower arch for six months full-time and six months part-time, clear plastic provided similar stability to Hawley retainers (LII MD 0.01 mm, 95% CI -0.65 to 0.67; 1 study, 30 participants). Hawley retainers had lower risk of failure (RR 0.60, 95% CI 0.43 to 0.83; 1 study, 111 participants), but were less comfortable at six months (VAS MD -1.86 cm, 95% CI -2.19 to -1.53; 1 study, 86 participants). Part-time versus full-time wear of Hawley There was no evidence of a difference in stability between part-time and full-time use of Hawley retainers (MD 0.20 mm, 95% CI -0.28 to 0.68; 1 study, 52 participants). AUTHORS' CONCLUSIONS: The evidence is low to very low certainty, so we cannot draw firm conclusions about any one approach to retention over another. More high-quality studies are needed that measure tooth stability over at least two years, and measure how long retainers last, patient satisfaction and negative side effects from wearing retainers, such as tooth decay and gum disease.

ANTECEDENTES: Sin una fase de retención tras un tratamiento de ortodoncia exitoso, los dientes tienden a "recaer", es decir, a volver a su posición inicial. La retención se consigue colocando retenedores fijos o removibles para proporcionar estabilidad a los dientes y evitar al mismo tiempo daños en dientes y encías. Los retenedores removibles pueden llevarse a tiempo completo o parcial. Los retenedores varían en la forma, el material y el modo de fabricación. A veces se utilizan procedimientos complementarios para intentar mejorar la retención, por ejemplo, remodelando los dientes en la zona de contacto ("reducción interproximal") o cortando fibras alrededor de los dientes ("pericisión"). Esta revisión es una actualización de una publicada originalmente en 2004 y actualizada por última vez en 2016. OBJETIVOS: Evaluar los efectos de los diferentes retenedores y estrategias de retención utilizados para estabilizar la posición de los dientes después del tratamiento con aparatos de ortodoncia. MÉTODOS DE BÚSQUEDA: Un documentalista realizó búsquedas en el Registro de ensayos del Grupo Cochrane de Salud oral (Cochrane Oral Health), en CENTRAL, MEDLINE, Embase y OpenGrey hasta el 27 de abril de 2022 y utilizó métodos de búsqueda adicionales para identificar estudios publicados, no publicados y en curso. CRITERIOS DE SELECCIÓN: Ensayos controlados aleatorizados (ECA) con niños y adultos a los que se les colocaron retenedores o se les realizaron procedimientos complementarios para prevenir la recaída tras el tratamiento con aparatos de ortodoncia. Se excluyeron los estudios con alineadores. OBTENCIÓN Y ANÁLISIS DE LOS DATOS: Dos autores de la revisión realizaron de forma independiente la revisión de los estudios elegibles, evaluaron el riesgo de sesgo y extrajeron los datos. Los desenlaces fueron la estabilidad o recaída de la posición dental, el fracaso del retenedor (es decir, roto, desprendido, desgastado, mal ajustado o perdido), los efectos adversos en dientes y encías (es decir, índices de placa, gingivales y de sangrado) y la satisfacción de los participantes. Se calcularon las diferencias de medias (DM) para los datos continuos, las razones de riesgos (RR) o las diferencias de riesgos (DR) para los datos dicotómicos, y los cociente de riesgos instantáneos (CRI) para los datos de supervivencia, todos ellos con intervalos de confianza (IC) del 95%. Se realizaron metanálisis cuando estudios similares informaron desenlaces en el mismo punto temporal; de lo contrario, los resultados se informaron como rangos medios. Se dio prioridad a la notificación del Little's Irregularity Index (torcedura de los dientes anteriores) para medir la recaída, considerando que la diferencia mínima importante era de 1 mm. RESULTADOS PRINCIPALES: Se incluyeron 47 estudios con 4377 participantes. Los estudios evaluaron: retenedores removibles versus fijos (ocho estudios); diferentes tipos de retenedores fijos (22 estudios) o materiales adhesivos (tres estudios); y diferentes tipos de retenedores removibles (16 estudios). Cuatro estudios evaluaron más de una comparación. Se consideró que 28 estudios tenían un alto riesgo de sesgo, 11 un riesgo bajo y en ocho estudios fue incierto. El centro de atención de esta revisión fue el seguimiento a los 12 meses. La evidencia es de certeza baja a muy baja. La mayoría de las comparaciones y los desenlaces se evaluaron en un solo estudio con alto riesgo de sesgo, y la mayoría de los estudios midieron los desenlaces después de menos de un año. Retenedores removibles versus fijos Removible (a tiempo parcial) versus fijo Un estudio informó que los participantes que llevaban retenedores de plástico transparente a tiempo parcial en la arcada inferior presentaron más recaídas que los participantes con retenedores fijos de múltiples barras, pero la cantidad no fue clínicamente significativa (Little's Irregularity Index [IIL] DM 0,92 mm; IC del 95%: 0,23 a 1,61; 56 participantes). Los retenedores removibles tuvieron más probabilidades de causar molestias (RR 12,22; IC del 95%: 1,69 a 88,52; 57 participantes), pero se asociaron con menos fracaso del retenedor (RR 0,44; IC del 95%: 0,20 a 0,98; 57 participantes) y mejor salud periodontal (Gingival Index [IG] DM ­0,34; IC del 95%: ­0,66 a ­0,02; 59 participantes). Removible (a tiempo completo) versus fijo Un estudio informó que los retenedores removibles de plástico transparente utilizados a tiempo completo en la arcada inferior no proporcionaron efectos beneficiosos clínicamente significativos en la estabilidad dental en comparación con los retenedores fijos (LII DM 0,60 mm; IC del 95%: 0,17 a 1,03; 84 participantes). Los participantes con retenedores de plástico transparente tenían mejor salud periodontal (sangrado gingival RR 0,53; IC del 95%: 0,31 a 0,88; 84 participantes), pero mayor riesgo de fracaso del retenedor (RR 3,42; IC del 95%: 1,38 a 8,47; 77 participantes). El estudio no encontró diferencias entre los retenedores en las caries. Diferentes tipos de retenedores fijos De nitinol con diseño asistido por ordenador/fabricación asistida por ordenador (DAO/FAO) versus de múltiples barras convencional/analógico Un estudio informó que los retenedores fijos de nitinol con DAO/FAO fueron mejores para la estabilidad dental, pero la diferencia no fue clínicamente significativa (LII DM ­0,46 mm; IC del 95%: ­0,72 a ­0,21; 66 participantes). No hubo evidencia de una diferencia entre los retenedores en la salud periodontal (GI MD 0,00; IC del 95%: ­0,16 a 0,16; dos estudios, 107 participantes) ni en la supervivencia del retenedor (RR 1,29; IC del 95%: 0,67 a 2,49; un estudio, 41 participantes). Composite reforzado con fibra versus alambre de múltiples barras/en espiral convencional Un estudio informó que los retenedores fijos de composite reforzado con fibra proporcionaron una mayor estabilidad que los retenedores de múltiples barras, pero no fue clínicamente significativa (LII DM ­0,70 mm; IC del 95%: ­1,17 a ­0,23; 52 participantes). Los retenedores reforzados con fibra tuvieron una mejor satisfacción del paciente con respecto a la estética (DM 1,49 cm en una escala visual analógica; IC del 95%: 0,76 a 2,22; un estudio, 32 participantes) y tasas similares de supervivencia del retenedor (RR 1,01, IC del 95%: 0,84 a 1,21; siete estudios; 1337 participantes) a los 12 meses. Sin embargo, los fracasos se produjeron antes (DM ­1,48 meses; IC del 95%: ­1,88 a ­1,08; dos estudios, 103 participantes; seguimiento de 24 meses) y más inflamación gingival a los seis meses, aunque el sangrado al sondaje (SS) fue similar (GI DM 0,59; IC del 95%: 0,13 a 1,05; SS DM 0,33; IC del 95%: ­0,13 a 0,79; un estudio, 40 participantes). Diferentes tipos de retenedores removibles Plástico transparente versus Hawley Cuando se llevó en la arcada inferior durante seis meses a tiempo completo y seis meses a tiempo parcial, el plástico transparente proporcionó una estabilidad similar a los retenedores Hawley (LII DM 0,01 mm; IC del 95%: ­0,65 a 0,67; un estudio, 30 participantes). Los retenedores Hawley tuvieron un menor riesgo de fracaso (RR 0,60; IC del 95%: 0,43 a 0,83; un estudio, 111 participantes), pero resultaron menos cómodos a los seis meses (EVA DM ­1,86 cm; IC del 95%: ­2,19 a ­1,53; un estudio, 86 participantes). Hawley a tiempo parcial versus a tiempo completo No hubo evidencia de una diferencia en la estabilidad entre el uso a tiempo parcial y a tiempo completo de los retenedores Hawley (DM 0,20 mm; IC del 95%: ­0,28 a 0,68; un estudio, 52 participantes). CONCLUSIONES DE LOS AUTORES: La evidencia es de certeza baja a muy baja, por lo que no fue posible establecer conclusiones firmes sobre un método de retención en detrimento de otro. Se necesitan más estudios de alta calidad que midan la estabilidad de los dientes durante al menos dos años, así como la duración de los retenedores, la satisfacción de los pacientes y los efectos secundarios negativos del uso de retenedores, como caries y enfermedades de las encías.

Retention procedures for stabilising tooth position after treatment with orthodontic braces.

BACKGROUND: Retention is the phase of orthodontic treatment that attempts to keep teeth in the corrected positions after treatment with orthodontic braces. Without a phase of retention, there is a tendency for teeth to return to their initial position (relapse). To prevent relapse, almost every person who has orthodontic treatment will require some type of retention. OBJECTIVES: To evaluate the effects of different retention strategies used to stabilise tooth position after orthodontic braces. SEARCH METHODS: We searched the following databases: the Cochrane Oral Health Group's Trials Register (to 26 January 2016), the Cochrane Central Register of Controlled Trials (CENTRAL) (2015, Issue 12), MEDLINE via Ovid (1946 to 26 January 2016) and EMBASE via Ovid (1980 to 26 January 2016). We searched for ongoing trials in the US National Institutes of Health Trials Register (ClinicalTrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform. We applied no language or date restrictions in the searches of the electronic databases. We contacted authors of randomised controlled trials (RCTs) to help identify any unpublished trials. SELECTION CRITERIA: RCTs involving children and adults who had had retainers fitted or adjunctive procedures undertaken to prevent relapse following orthodontic treatment with braces. DATA COLLECTION AND ANALYSIS: Two review authors independently screened eligible studies, assessed the risk of bias in the trials and extracted data. The outcomes of interest were: how well the teeth were stabilised, failure of retainers, adverse effects on oral health and participant satisfaction. We calculated mean differences (MD) with 95% confidence intervals (CI) for continuous data and risk ratios (RR) with 95% CI for dichotomous outcomes. We conducted meta-analyses when studies with similar methodology reported the same outcome. We prioritised reporting of Little's Irregularity Index to measure relapse. MAIN RESULTS: We included 15 studies (1722 participants) in the review. There are also four ongoing studies and four studies await classification. The 15 included studies evaluated four comparisons: removable retainers versus fixed retainers (three studies); different types of fixed retainers (four studies); different types of removable retainers (eight studies); and one study compared a combination of upper thermoplastic and lower bonded versus upper thermoplastic with lower adjunctive procedures versus positioner. Four studies had a low risk of bias, four studies had an unclear risk of bias and seven studies had a high risk of bias. Removable versus fixed retainers Thermoplastic removable retainers provided slightly poorer stability in the lower arch than multistrand fixed retainers: MD (Little's Irregularity Index, 0 mm is stable) 0.6 mm (95% CI 0.17 to 1.03). This was based on one trial with 84 participants that was at high risk of bias; it was low quality evidence. Results on retainer failure were inconsistent. There was evidence of less gingival bleeding with removable retainers: RR 0.53 (95% CI 0.31 to 0.88; one trial, 84 participants, high risk of bias, low quality evidence), but participants found fixed retainers more acceptable to wear, with a mean difference on a visual analogue scale (VAS; 0 to 100; 100 being very satisfied) of -12.84 (95% CI -7.09 to -18.60). Fixed versus fixed retainersThe studies did not report stability, adverse effects or participant satisfaction. It was possible to pool the data on retention failure from three trials that compared polyethylene ribbon bonded retainer versus multistrand retainer in the lower arch with an RR of 1.10 (95% CI 0.77 to 1.57; moderate heterogeneity; three trials, 228 participants, low quality evidence). There was no evidence of a difference in failure rates. It was also possible to pool the data from two trials that compared the same types of upper fixed retainers, with a similar finding: RR 1.25 (95% CI 0.87 to 1.78; low heterogeneity; two trials, 174 participants, low quality evidence). Removable versus removable retainersOne study at low risk of bias comparing upper and lower part-time thermoplastic versus full-time thermoplastic retainer showed no evidence of a difference in relapse (graded moderate quality evidence). Another study, comparing part-time and full-time wear of lower Hawley retainers, found no evidence of any difference in relapse (low quality evidence). Two studies at high risk of bias suggested that stability was better in the lower arch for thermoplastic retainers versus Hawley, and for thermoplastic full-time versus Begg (full-time) (both low quality evidence).In one study, participants wearing Hawley retainers reported more embarrassment more often than participants wearing thermoplastic retainers: RR 2.42 (95% CI 1.30 to 4.49; one trial, 348 participants, high risk of bias, low quality evidence). They also found Hawley retainers harder to wear. There was conflicting evidence about survival rates of Hawley and thermoplastic retainers. Other retainer comparisonsAnother study with a low risk of bias looked at three different approaches to retention for people with crowding, but normal jaw relationships. The study found that there was no evidence of a difference in relapse between the combination of an upper thermoplastic and lower canine to canine bonded retainer and the combination of an upper thermoplastic retainer and lower interproximal stripping, without a lower retainer. Both these approaches are better than using a positioner as a retainer. AUTHORS' CONCLUSIONS: We did not find any evidence that wearing thermoplastic retainers full-time provides greater stability than wearing them part-time, but this was assessed in only a small number of participants.Overall, there is insufficient high quality evidence to make recommendations on retention procedures for stabilising tooth position after treatment with orthodontic braces. Further high quality RCTs are needed.

Orthodontic retention: a systematic review.

OBJECTIVE: To evaluate the effectiveness of different retention strategies used to maintain tooth position after treatment by orthodontic appliances. DATA SOURCES: The search strategy was carried out according to the standard Cochrane systematic review methodology. The following databases were searched for randomized clinical trials (RCT) or controlled clinical trials (CCT): Cochrane Oral Health Group Trials Register, Cochrane Clinical Trials Register, MEDLINE and EMBASE. No language restrictions were applied. Authors of trials were contacted to identify unpublished trials. Inclusion and exclusion criteria were applied when considering the studies to be included and a quality assessment made for each paper. DATA SELECTION: The primary outcome was the amount of relapse. Secondary outcomes were survival of retainers, adverse effects on oral health and patient satisfaction. DATA EXTRACTION: Screening of eligible studies, assessment of the methodological quality of the trials and data extraction were conducted in duplicate and independently by two reviewers. Five studies (2 RCTs and 3 CCTs) fulfilled the inclusion criteria. DATA SYNTHESIS: There was evidence, based on data from one trial, that there was a statistically significant increase in stability in both the mandibular (P<0.001) and maxillary anterior segments (P<0.001) when the CSF (circumferential supracrestal fiberotomy) was used in conjunction with a Hawley retainer, compared with a Hawley retainer alone. However, this evidence may be unreliable due to flaws in the study design. There was also weak, unreliable evidence that teeth settle quicker with a Hawley retainer than with a clear overlay retainer after 3 months. CONCLUSIONS: There is currently insufficient evidence on which to base the clinical practice of orthodontic retention.