Background: Bonded retainers are widely used to maintain the positions of anterior teeth after orthodontic treatment. Various types of bonded retainer exist however, there is a lack of evidence to indicate which type is superior.
Aim: To compare upper and lower CAD/CAM nitinol bonded retainers (Memotain®) with upper and lower chairside rectangular-chain bonded retainers (Ortho-FlexTech™), in terms of stability, retainer failures and patient satisfaction.
Trial design: Multi-centre, two-arm, parallel-group, randomised controlled clinical trial with 1:1 allocation.
Setting: Three trial centres: University Teaching Hospital; District General Hospital; and Specialist Orthodontic Practice. All treatment was provided free as part of a state-funded healthcare system.
Materials and methods: A total of 68 patients were randomly allocated to receive either upper and lower Memotain® bonded retainers or upper and lower Ortho-FlexTech™ bonded retainers. Ten trained operators placed and reviewed the bonded retainers. Measurements were carried out on study models taken at debond and after six months. Patient satisfaction questionnaires were completed at six months following debond.
Results: The trial was terminated due to the high number of failures (50%) of the upper Memotain® retainers within six months. Memotain® retainers were three times more likely to fail (unadjusted hazard ratio = 2.82, 95% confidence interval = 1.00-7.99) than Ortho-FlexTech™ retainers at six months in the upper arch. Patients were satisfied with both types of retainer.
Limitations: Early termination of the trial means that the a priori sample size was not reached, so outcomes should be interpreted with caution.
Conclusion: The trial was terminated early due to the high failure rate of upper Memotain® bonded retainers. They had a higher risk of failure in the maxillary arch when compared to upper Ortho-FlexTech™ bonded retainers after six months.
Keywords: Failure; Patient satisfaction; Randomised controlled trial; Retainers; Retention; Stability.