***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: In the United Kingdom ( UK ) over the last 10 years , there has been a significant increase in the use of vacuum-formed retainers ( VFRs ) rather than conventional Hawley retainers . There are currently no data to compare the cost-effectiveness of this change in practice . The two aims of this study were to compare ( 1 ) the cost-effectiveness of VFRs and Hawley retainers over 6 months , from the perspective of the National Health Service , orthodontic practice , and the patient and ( 2 ) patient satisfaction in the two retainer groups . A r and omized controlled trial ( RCT ) was carried out in a specialist orthodontic practice . Three hundred and ninety-seven eligible patients were r and omized to one of two retainer groups , and followed up for 6 months . All subjects were invited to complete patient satisfaction question naires . Additional data were collected for the cost analysis from the patient records and national data bases . Descriptive and bivariate analyses were used to compare patient satisfaction between retainer groups . In all , 196 subjects were r and omized to the Hawley group ( mean age 14 years 8 months , 63 per cent female , 37 per cent male ) and 201 to the VFR group ( mean age 15 years , 59 per cent female , 41 per cent male ) .  VFRs were more cost-effective than  Hawley retainers  from all perspectives . The majority of subjects showed a preference for VFRs compared with Hawley retainers . There were also fewer breakages than in the Hawley group OBJECTIVE To evaluate three different retention methods in compliant patients after 2 years of retention . DESIGN Three group r and omized controlled trial . MATERIAL S AND METHODS The sample was recruited from patients having their fixed appliance treatment between 2001 and 2007 . Seventy-five patients ( 45 girls and 30 boys with a mean age of 14.4 years at start of retention ) were r and omized into three retention methods : vacuum-formed retainer in the maxilla and bonded canine-to-canine retainer in the m and ible ( Group V-CTC ) , vacuum-formed retainer in the maxilla combined with stripping of the 10 proximal surfaces of the lower m and ibular anterior teeth ( Group V-S ) and prefabricated positioner covering the teeth in the maxilla and the m and ible ( Group P ) . The following linear measurements were performed : Little 's irregularity index ( LII ) , intercanine width , intermolar width , arch length , overjet , overbite and body height growth . Registration s were made before orthodontic treatment , at start of retention , after 12 and finally 24 months in retention . Differences in means between groups were tested by one-way analysis of variance ( SPSS ) . RESULTS After 2 years all three retention methods were successful in retaining orthodontic treatment results . The major part of relapse took place during the 1st year of retention . CONCLUSIONS All 3 types of retention methods were equally effective in controlling relapse to a clinical ly acceptable level The purpose of this study was to evaluate the periodontal tissues of patients with m and ibular fixed retention for long or short periods of time . A total of 64 individuals were selected for this study using the following inclusion criteria : long-term  lingual fixed retention ; identical type of lingual fixed retainer bonded with the same material s ; no cavities , restorations , or fractures of the m and ibular anterior teeth ; absence of habits and occlusal interferences ; and canine guidance bilaterally . The result ant sample comprised 32 patients ( mean age 25 years ) who had been in retention for a mean period of 9.65 years ( range 9 - 11 years ) and an equal number retained for a period between 3 and 6 months .  Plaque , gingival , and calculus indices , probing pocket depth , marginal recession , and bone level at the m and ibular six anterior teeth were recorded for both groups . Demographic , clinical , and radiographic data were investigated with conventional descriptive statistics . Comparisons of the different variables between the two participant groups ( long- and short-term retention ) were carried out using a Mann-Whitney test for indices ( plaque , gingival , and calculus ) , and a Fisher 's exact test ( two sided ) for the remaining variables . No significant difference was found with respect to the plaque and gingival indices and bone level between the two groups . The long-term group presented higher calculus accumulation , greater marginal recession , and increased probing depth ( P < 0.05 ) . The results of this study raise the question of the appropriateness of lingual fixed retainers as a st and ard retention plan for all patients regardless of their attitude to dental hygiene . They also emphasize the importance of individual variability and cautious application of retention protocol s after a thorough consideration of issues related to the anatomy of tissues and oral hygiene Background The aim of this prospect i ve clinical study was to compare the mean durability and the failure rates of two types of orthodontic retainers . Methods Orthodontic patients ( 142 ) aged between 14 and 28 years were recruited in this study . The polyethylene woven ribbon ( Ribbond , Seattle , WA , USA ) retainer was compared with a 0.0175-in flexible spiral wire ( Respond , Ormco , Glendora , CA , USA ) retainer . When treatment was completed , the retainers were bonded from canine to canine in the maxillary and the m and ibular arches of the participants . In the follow-up visits , the patients were re-evaluated every 3 months over a period of 18 months . The time taken for the retainers to remain without any fracture was appraised . Kaplan-Meier analysis and the logrank test were employed to identify significant differences in the survival functions between the groups . The rates of the retainers ' failure between the groups were analyzed using Chi-square test . Results It was revealed that the mean survival of the flexible spiral wire retainer was 15.34 ± 0.47 and 15.60 ± 0.42 months in the maxillary and m and ibular arches , respectively . The mean survival of the ribbon retainer was 13.95 ± 0.55 and 14.26 ± 0.57 months in the maxillary and m and ibular arches , respectively . Ribbon retainers showed a failure rate of 50 % in the maxillary and 42.6 % in the m and ibular arches . Flexible spiral retainers showed a failure rate of 36.5 % in the maxillary and 37.8 % in the m and ibular arches . The differences were not statistically significant . Regarding the evaluation period , the differences had limited clinical significance . Conclusion The mean survival time and the failure rates of the polyethylene woven ribbon retainer were comparable to the flexible spiral wire retainer during the 18 months after orthodontic treatment AIM To present an overview of the main components of r and omised controlled trials and identify issues for consideration during their design and management . BACKGROUND R and omised controlled trials ( RCTs ) are considered to be the gold st and ard for determining causality and can provide high quality evidence to inform nursing practice . DATA SOURCES A search of online data bases and websites was undertaken to identify relevant contemporary literature to inform the discussion . DISCUSSION / CONCLUSION Conducting a robust r and omised controlled trial can present research ers with numerous challenges and practical considerations . The importance of taking account of the Consort guidelines during their design , conduct and reporting is emphasised . IMPLICATION S FOR RESEARCH / PRACTICE Evidence from well conducted RCTs contributes to the development of effective nursing interventions . To avoid bias and ensure valid results , the design , conduct and reporting of RCTs should follow the Consort guidelines . Service users should be involved in the design and management of RCTs The aim of this r and omized clinical trial was to carry out a biometric comparison between the orthodontic extrusion ( OE , group B )  technique and  OE combined with fiberotomy and root planing  ( OEFRP , group A ) . Twenty single-root teeth were extruded and assigned to two different groups . In both groups , fixed orthodontic appliances were activated weekly during the course of 3 weeks . After activation , the extruded teeth were maintained in retention for a period of 8 weeks . In group A , along with weekly activation , fiberotomy and root planing were carried out on the top of the alveolar bone crest . Statistical analysis revealed that the amount of dental structure exposed was greater in group A , where the gingival margin and bone tissue remained stable ( P < .05 ) . Group B presented coronal migration of the gingival tissue and bone tissue of 2 mm and 1.5 mm , respectively The aim of this prospect i ve study was to evaluate and compare stability after 6 months of Essix retainer use . Patients ' perceptions of wearing the retainer were also evaluated . A total of 69 patients , 53 girls and 16 boys [ mean age 15.7 years , st and ard deviation ( SD ) 1.96 ] , were included in the study and r and omized into two groups with different wear regimens ; full-time wear for 3 months and thereafter at night ( group A ) compared to full-time wear for 1 week and thereafter at night only ( group B ) . Sixty patients completed the study and thus , group A comprised 30 maxillary retainers and 18 m and ibular retainers and group B 30 maxillary and 18 m and ibular retainers .  Little 's irregularity index ( LII ) , overjet , and overbite were measured at debond ( T(1 ) ) and after 6 months ( T(2 ) ) . Differences within and between groups were analysed with a Mann-Whitney test . At T(2 ) , all patients completed a question naire in order to evaluate their experience of wearing an Essix retainer and how they complied with the given instructions . Differences in LII during T(1)-T(2 ) were 0.44 and 0.49 mm for group A and B , respectively , but with no significant difference between the groups . There were also no significant changes in overjet and overbite within or between the groups during T(1)-T(2 ) . According to the responses to the question naire , the retainer was well tolerated by the patients . It was therefore concluded that the Essix retainer is sufficient for maintaining the results after orthodontic treatment and that night-time wear is adequate INTRODUCTION The objective of this trial was to compare the survival rates of m and ibular lingual retainers  bonded with either chemically cured or light-cured adhesive  after orthodontic treatment . METHODS Patients having undergone orthodontic treatment at a private orthodontic office were r and omly allocated to fixed retainers placed with chemically cured composite or light-cured composite .  Eligibility criteria included no active caries , restorations , or fractures on the m and ibular anterior teeth , and adequate oral hygiene . The main outcome was any type of first-time lingual retainer breakage ; pattern of failure ( adapted adhesive remnant index scores ) was a secondary outcome . R and omization was accomplished with r and om permuted blocks of 20 patients with allocation concealed in sequentially numbered , opaque , sealed envelopes . Blinding was applicable for outcome assessment only . Patients were review ed at 1 , 3 , and 6 months and then every 6 months after placement of the retainer until completion of the study . Data were analyzed using survival analysis including Cox regression ; sensitivity analysis was carried out after data imputation for subjects lost to follow-up . RESULTS Two hundred twenty patients ( median age , 16 years ; interquartile range , 2 ; range , 12 - 47 years ) were r and omized in a 1:1 ratio to either chemical or light curing . Baseline characteristics were similar between groups , the median follow-up period was 2.19 years ( range , 0.003 - 3.64 years ) , and 16 patients were lost to follow-up . At a minimum follow-up of 2 years , 47 of 110 ( 42.7 % ) and 55 of 110 ( 50.0 % ) retainers had some type of failure with chemically cured and light-cured adhesive , respectively ( log-rank test , P = 0.35 ) . Data were analyzed on an intention-to-treat basis , and the hazard ratio ( HR ) was 1.15 ( 95 % confidence interval [ CI ] , 0.88 - 1.70 ; P = 0.47 ) . There was weak evidence that age is a significant predictor for lingual retainer failures ( HR , 0.96 ; 95 % CI , 0.93 - 1.00 ; P = 0.08 ) . Adhesive remnant index scoring was possible for only 66 of the 102 ( 64.7 % ) failures and did not differ between composites ( Fisher exact test , P = 0.16 ) . No serious harm was observed other than gingivitis associated with plaque accumulation . CONCLUSIONS The results of this study indicated no evidence that survival of m and ibular lingual retainers differs between chemically and light-cured adhesives . The overall failure rate was 46.4 % ; however , this included any type of failure , which may have exaggerated the overall failure rate OBJECTIVE The reliability of posttreatment canine-to-canine retention with resin composite retainers reinforced with plasma-treated woven polyethylene ribbons was compared to the reliability of directly bonded , multistr and ed wire retainers . METHOD AND MATERIAL S This prospect i ve study was based on an assessment of 20 consecutive patients ( eight women and 12 men with a mean age of 22.4 years ) who required a fixed canine-to-canine retainer after undergoing orthodontic treatment . The type of retainer used was r and omized for each patient . A follow-up examination was carried out once every 3 months . The length of time the retainers stayed in place without resin fracture or loosening from the teeth at one 
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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 .
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 .