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Table 3 Quality assessment of the included RCT studies

From: Clinical effectiveness of Invisalign® orthodontic treatment: a systematic review

Author-year of publication Study design Sequence generation (selection bias) Allocation concealment (selection bias) Blinding of participants and personnel (performance bias) Blinding of outcome assessors (detection bias) Incomplete outcome data (attrition bias) Selective reporting (reporting bias) Other sources of bias Overall risk
Hennessy et al. [18] (2016) RCT Aj: Low risk Sfj: Although not explicitly stated, sequence generation is very likely due to reference of random picking up of sealed opaque envelopes Aj: Low risk Sfj: Sealed opaque, envelopes Aj: Low risk Sfj: Incomplete blinding, but the review authors judge that the outcome is not likely to be influenced by lack of blinding Aj: Low risk Sfj: No blinding of outcome assessment, but the review authors judge that the outcome measurement is not likely to be influenced by lack of blinding Aj: Low risk Sfj: Missing outcome data balanced in numbers across intervention groups, with similar reasons for missing data across groups Aj: Low risk Sfj: The study protocol is available and all of the study’s pre-specified outcomes that are of interest in the review have been reported in the pre-specified way Aj: Low risk Sfj: The study appears to be free of other sources of bias Low
Li et al. [19] (2015) RCT Aj: Low risk Sfj: Use of a computer random number generator Aj: Low risk Sfj: Sequentially numbered, opaque, sealed envelopes Aj: Low risk Sfj: Blinding ensured and unlikely that the blinding could have been broken Aj: Low risk Sfj: Blinding of outcome assessment ensured and unlikely that the blinding could have been broken Aj: Low risk Sfj: No missing outcome data Aj: Low risk Sfj: The study protocol is available and all of the study’s pre-specified outcomes that are of interest in the review have been reported in the pre-specified way Aj: Low risk Sfj: The study appears to be free of other sources of bias Low
Bollen et al. [20] (2003) RCT Aj: Low risk Sfj: Reference to a random number list Aj: Low risk Sfj: Randomization schedule based on a list of random numbers performed by a calibrated investigator, unaware of the treatment plan Aj: Low risk Sfj: Incomplete blinding, but the review authors judge that the outcome is not likely to be influenced by lack of blinding Aj: Low risk Sfj: No blinding of outcome assessment, but the review authors judge that the outcome measurement is not likely to be influenced by lack of blinding Aj: Low risk Sfj: Missing outcome data balanced in numbers across intervention groups, with similar reasons for missing data across groups Aj: Low risk Sfj: The study protocol is available and all of the study’s pre-specified outcomes that are of interest in the review have been reported in the pre-specified way Aj: Low risk Sfj: The study appears to be free of other sources of bias Low
  1. Aj: authors’ judgment, Sfj support for judgment