Summary of findings 3. Removable retainer versus removable retainer to stabilise tooth position.

Removable retainer versus removable retainer to stabilise tooth position
Patient or population: people who have received fixed appliance treatment Setting: specialist practice, university or hospital orthodontic department Intervention: one type of removable retainer or wear time Comparison: another type of removable retainer or wear time
Outcomes	Anticipated absolute effects* (95% CI)		Relative effect (95% CI)	No of participants (studies)	Quality of the evidence (GRADE)	Comments
	Risk with Removable Retainers	Risk with Removable
Stability ‐ Little's Irregularity Index in upper arch Ideally 0 mm 12 months	‐	‐	‐	419 (3 RCT)	⊕⊕⊝⊝ low to ⊕⊕⊕⊝ moderate	Data used from 3 studies comparing different removable retainers used for different time periods 1 study at low risk of bias comparing part‐time thermoplastic vs. full‐time thermoplastic retainer showed no evidence to suggest a difference (graded moderate quality evidence: downgraded once due to imprecision). There was also data from additional study with a low risk of bias that could not be analysed using Review Manager 5 that suggested no evidence of difference in relapse when thermoplastic retainers were worn full‐time or part‐time 1 study comparing part‐time and full‐time Hawley retainers showed no evidence of a difference (graded low quality of evidence: downgraded twice due to high risk of bias and imprecision) 1 study at high risk of bias comparing upper Hawley retainers and upper thermoplastic retainers suggested there was statistical, but not clinically significant, reductions in relapse with thermoplastic retainers (graded low quality: downgraded twice due to high risk of bias and imprecision)
Stability ‐ Little's Irregularity Index in lower arch Ideally 0 mm 6‐12 months	‐	‐	‐	643 (4 RCT)	⊕⊕⊝⊝ low to ⊕⊕⊕⊝ moderate	Data used from 4 studies comparing different removable retainers used for different time periods. 1 study at low risk of bias comparing part‐time thermoplastic vs. full‐time thermoplastic retainer showed no evidence to suggest a difference (graded moderate quality evidence, downgraded once due to imprecision) 2 studies at high risk of bias suggested that stability was better for thermoplastic retainers vs. Hawley retainers, and for thermoplastic full‐time retainers vs. Begg (full‐time) retainers (both low quality evidence; downgraded twice due to high risk of bias and imprecision) 1 study with a high risk of bias comparing part‐time and full‐time wear of lower Hawley retainers found no evidence of any difference in relapse (low quality evidence: downgraded twice due to high risk of bias and imprecision). Data from an additional study with a low risk of bias that could not be analysed using Review Manager to support this evidence
Failure of retainers How many broke in total? 12 months	‐	‐	‐	457 (2 RCTs)	⊕⊕⊝⊝ low	2 studies provided data 1 study comparing Hawley retainers vs. part‐time thermoplastic retainers showed no difference in the number of retainers that were lost (low quality evidence, downgraded twice due to high risk of bias) 1 study with a high risk of bias comparing full‐time wear of Hawley retainers vs. full‐time thermoplastic retainers found greater failure rates in the lower thermoplastic retainers (low quality evidence, downgraded twice due to high risk of bias, and imprecision)
Adverse effects on health	‐	‐	‐	0 (0)	‐	Not reported
Patient satisfactionEmbarrassed to wear retainer? 12 months	721 per 1000	174 per 1000 (93 to 322)	RR 2.42 (1.30 to 4.49)	348 (1 RCT)2	⊕⊕⊝⊝ low	1 study comparing Hawley and thermoplastic retainers found participants who wore the Hawley retainers found them harder to wear as instructed, and judged them more negatively when comparing them to the fixed appliances they had worn. There was no evidence of a difference between the Hawley and thermoplastic retainer groups in terms of discomfort or ability to wear them away from home (low quality evidence, downgraded twice as one study with high risk of bias and imprecision)
*The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval; RCT: randomised controlled trial; RR: risk ratio
GRADE Working Group grades of evidence High quality: We are very confident that the true effect lies close to that of the estimate of the effect Moderate quality: We are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different Low quality: Our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect Very low quality: We have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect

¹ From study control group
 ² Hawley versus thermoplastic retainers