Vacuum-formed retainers more effective than Hawley retainers.

Design: A randomised controlled trial (RCT) was performed in a single orthodontic practice.

Intervention: The aim was to compare the clinical effectiveness of Hawley and vacuum-formed retainers (VFR) over a 6-month period of retention. Three hundred and ninety-seven patients were treated by a specialist orthodontist and randomly allocated to wear either Hawley retainers (n=196) or VFR (n=201).

Outcome Measure: A blinded examiner analysed the records of maxillary and mandibular dental casts at debond and at 6 months into retention, assessing tooth rotation mesial to the first permanent molar, intercanine and intermolar widths, and Little's Index of Irregularity.

Results: Three hundred and fifty-five individuals participated through to the conclusion of the trial, giving a completion rate of 89%. The results showed significantly greater changes in irregularity of the incisors in the Hawley group than in the VFR group at 6 months.

Conclusions: VRF are more effective than Hawley retainers at holding the correction of the maxillary and mandibular labial segments.