The document discusses evidence-based orthodontics. It begins with definitions of evidence and evidence-based dentistry. It then discusses the history and evolution of evidence-based practice from the 19th century to present day. The need for evidence-based orthodontics is described as providing patients with the currently best available care. Clinical scenarios are presented and critically appraised based on evidence from the literature. Different study designs and hierarchies of evidence are reviewed. The importance of evidence-based decision making in orthodontics is emphasized.