Table 3 Risk of bias of included articles

 Bias due to confounding

Assessment of baseline in of certain number of participants by age and malocclusion description

Assessment of the method of pain evaluation

Assessment of time of evaluation

 Bias in selection of participants into the study

Assessment of participants eligibility criteria

Evaluation of eligible participants exclusion or difference between the follow-up period

 Bias in classification of interventions

Assessment of the intervention status—use of the aligner was not properly described (change of the aligner)

Use of additional orthodontic methods to correct malocclusion (ex: MI, elastic)

Use of analgesic

 Bias due to deviations from intended interventions

Evaluation of the systematic differences between the intervention (group that used the aligner) and the comparison group when there is no information about the evaluation of the pain

Use of analgesic for pain relief during orthodontic treatment

 Bias due to missing data

In the event of loss of follow-up, incomplete collection of data and exclusion of participants from the analysis

 Bias in measurement of the outcomes

When assessments of pain perception were not reported or were measured with error

When not all the measures established in the different treatment times are presented

When the use of analgesic is mentioned or not

 Bias in selection of the reported results

Selective report of results when the effect of all measurements of results has not been fully reported