title: Meta-analyses and orthodontic evidence-based clinical practice in the 21 century.
abstract: BACKGROUND
  Aim of this systematic review was to assess the orthodontic related issues which currently provide the best evidence as documented by meta-analyses, by critically evaluating and discussing the methodology used in these studies.
  
  
  METHODS
  Several electronic databases were searched and handsearching was also performed in order to identify the corresponding meta-analyses investigating orthodontic related subjects. In total, 197 studies were retrieved initially. After applying specific inclusion and exclusion criteria, 27 articles were identified as meta-analyses treating orthodontic-related subjects.
  
  
  RESULTS
  Many of these 27 papers presented sufficient quality and followed appropriate meta-analytic approaches to quantitatively synthesize data and presented adequately supported evidence. However, the methodology used in some of them presented weaknesses, limitations or deficiencies. Consequently, the topics in orthodontics which currently provide the best evidence, include some issues related to Class II or Class III treatment, treatment of transverse problems, external apical root resorption, dental anomalies, such as congenital missing teeth and tooth transposition, frequency of severe occlusal problems, nickel hypersensitivity, obstructive sleep apnea syndrome, and computer-assisted learning in orthodontic education.
  
  
  CONCLUSIONS
  Only a few orthodontic related issues have been so far investigated by means of MAs. In addition, for some of these issues investigated in the corresponding MAs no definite conclusions could be drawn, due to significant methodological deficiencies of these studies. According to this investigation, it can be concluded that at the begin of the 21(st) century there is evidence for only a few orthodontic related issues as documented by meta-analyses, and more well-conducted high quality research studies are needed to produce strong evidence in order to support evidence-based clinical practice in orthodontics.
authors.affiliation: Associate Professor & Program Coordinator, Department of Orthodontics, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki, Greece.
authors.forename: Moschos A
authors.initials: MA
authors.lastname: Papadopoulos