Are orthodontic randomised controlled trials justified with a citation of an appropriate systematic review?

BACKGROUND: A systematic review of the evidence should be undertaken to support the justification for undertaking a clinical trial. The aim of this study was to examine whether reports of orthodontic Randomised Clinical Trials (RCTs) cite prior systematic reviews (SR) to explain the rationale or justification of the trial. Study characteristics that predicated the citation of SR in the RCT report were also explored. MATERIAL AND METHODS: Orthodontic RCTs published between 1st January 2010 to 31st December 2020 in seven orthodontic journals were identified. All titles and abstracts were screened independently by two authors. Descriptive statistics and associations were assessed for the study characteristics. Logistic regression was used to identify predicators of SR inclusion in the trial report. RESULTS: 301 RCTs fulfilling the eligibility criteria were assessed. 220 SRs were available of which 74.5% (N = 164) were cited, and 24.5% (N = 56) were not included but were available in the literature within 12 months of trial commencement. When a SR was not included in the introduction or no SR was available within 12 months of trial commencement, interventional studies were commonly cited. The continent of the corresponding author predicated the possibility of inclusion of a SR in the introduction (OR 0.36; 95% CI 0.18–0.71; p = 0.003). CONCLUSIONS: A quarter of orthodontic RCTs (24.5%) included in this study did not cite a SR in the introduction section to justify the rationale of the trial when a relevant SR was available. To reduce research waste and optimal usage of resources, researchers should identify or conduct a systematic review of the evidence to support the rationale and justification of the trial.