Historical controls in orthodontics: need for larger meta-epidemiological studies

Abstract

Dear Sir, In their meta-epidemiological study, Papageorgiou et al. (1) report on the impact of the design of untreated control groups on the magnitude of treatment effect size estimates in orthodontic trials. While the authors investigate an important research question with potential clinical relevance, there are some points that need to be considered when interpreting their results. First, the study in question included 122 trials involving different orthodontic interventions with large numbers of study outcomes; this number of …