title: Split-mouth designs in orthodontics: an overview with applications to orthodontic clinical trials.
abstract: Split-mouth designs first appeared in dental clinical trials in the late sixties. The main advantage of this study design is its efficiency in terms of sample size as the patients act as their own controls. Cited disadvantages relate to carry-across effects, contamination or spilling of the effects of one intervention to another, period effects if the interventions are delivered at different time periods, difficulty in finding similar comparison sites within patients and the requirement for more complex data analysis. Although some additional thought is required when utilizing a split-mouth design, the efficiency of this design is attractive, particularly in orthodontic clinical studies where carry-across, period effects and dissimilarity between intervention sites does not pose a problem. Selection of the appropriate research design, intervention protocol and statistical method accounting for both the reduced variability and potential clustering effects within patients should be considered for the trial results to be valid.
authors: * Department of Orthodontics and Dentofacial Orthopedics, Dental School, Medical Faculty, University of Bern, Switzerland.
authors: Nikolaos
authors: N
authors: Pandis
authors: Tanya
authors: T
authors: Walsh
authors: Argy
authors: A
authors: Polychronopoulou
authors: Christos
authors: C
authors: Katsaros
authors: Theodore
authors: T
authors: Eliades
mesh_terms: D002986:Clinical Trials as Topic; D006801:Humans; D009055:Mouth / Q000033:anatomy & histology*; D016382:Orthodontic Appliance Design / Q000379:methods*