Trial design and any changes after trial commencement
bleeding, coin toss
BLEEDING, RECRUITMENT
This study was a single-centre, single-operator, two-arm, parallel-group, stratified, single-blind RCT trial with a 1:1 allocation ratio, conducted in the Department of Orthodontics at York Hospital, UK.Changes after the commencement of the trial were as follows:Due to the COVID-19 pandemic, there was a reduced pool of potential participants. For the first 33 participants, stratified block randomisation was carried out based on age, gender and baseline interdental bleeding index. It is standard practice using stratified block randomisation that once enough participants in an individual block have been recruited, recruitment to this block would cease. However, the decision was made to continue recruiting patients who met the inclusion criteria, even if their block was full, and randomise them by a single coin toss, to ensure that the sample size was achieved (see ‘Sample size calculation’ below).An interim analysis of results was carried out due to issues with recruitment during the COVID-19 pandemic, and the ethical challenges associated with carrying out research in the already overstretched NHS. Following the analysis, the decision was made to stop the trial as there had been fewer dropouts than expected and the sample size had been reached. The decision was discussed with the trial sponsor and ethics committee. Any data collected between the initial interim analysis and the decision being made to stop the trial were included in this final analysis.