title: Randomized and nonrandomized studies: complementary or competing?
abstract: Both randomized and nonrandomized studies are integral to orthodontic research and practice because they permit evaluation of relationships between exposures and outcomes, allowing the efficacy, effectiveness, and safety of interventions to be assessed. These designs allow clinical decisions to be informed. Nonrandomized designs include nonrandomized clinical trials, cohort studies, case-control studies, cross-sectional studies, case series, and ecological studies. There is debate surrounding the optimal research design; however, both randomized and nonrandomized designs are important to build a broad, informative evidence base. The designs are therefore complementary, with unique advantages and limitations. The applicability of either approach hinges on the clinical question posed, the feasibility of studying it, and ethical considerations.
authors.affiliation: Visiting assistant professor, Department of Orthodontics and Dentofacial Orthopedics, School of Dental Medicine, Medical Faculty, University of Bern, Bern, Switzerland. Electronic address: npandis@yahoo.com.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Pandis
authors.affiliation: Associate professor, Graduate Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, Taipei, Taiwan.
authors.forename: Yu-Kang
authors.initials: YK
authors.lastname: Tu
authors.affiliation: Senior clinical lecturer and honorary consultant, Barts and the London School of Medicine and Dentistry, Queen Mary University, London, United Kingdom.
authors.forename: Padhraig S
authors.initials: PS
authors.lastname: Fleming
authors.affiliation: Associate professor, Department of Preventive and Community Dentistry, School of Dentistry, University of Athens, Athens, Greece.
authors.forename: Argy
authors.initials: A
authors.lastname: Polychronopoulou
mesh_terms: D015982:Bias; D016022:Case-Control Studies; D015331:Cohort Studies; D015986:Confounding Factors, Epidemiologic; D018865:Dental Research; D055094:Evidence-Based Dentistry; D006801:Humans; D065228:Non-Randomized Controlled Trials as Topic; D009970:Orthodontics; D016032:Randomized Controlled Trials as Topic; D012107:Research Design; D012449:Safety; D016896:Treatment Outcome