Evidence - Based Medicine is the integration of best research evidence with clinical expertise and patient values. (Sackett DL, Straus SE, Richardson WS, et. al. Evidence - based medicine: how to practice and teach EBM. 2nded. Edinburg: Churchill Livingstone, 2000)
ADA definition of Evidence-based dentistry (EBD): an approach to oral health care that requires the judicious integration of systematic assessments of clinically relevant scientific evidence, relating to the patient's oral and medical condition and history, with the dentist's clinical expertise and the patient's treatment needs and preferences.
Quality of Evidence ranges from A (High) - several high-quality studies with consistent results - to D (very low) - expert opinion, no direct research evidence, or one or more studies with very severe limitation (Essential Evidence Plus. (2009). Levels of Evidence. Malden, MA: John Wiley).