
Randomization (random number generation, allocation concealment, implementation)

Participants were randomly allocated to either multi-strand wire or Ortho-Flex-Tech™ rectangular wire retainers. Randomization sequence was created using Excel 2010 (Microsoft, Redmond, WA, USA), with a 1:1 allocation, using random block size 4. Allocation concealment was applied before the trial commencement, to prevent selection bias. The allocation sequence was concealed in sequentially numbered, opaque and sealed envelopes from the investigator responsible for assigning participants into the intervention groups (K.A.), until the time of allocation implementation. Randomization sequence creation and allocation concealment were applied by another investigator (E.A.).