Introduction

Scientific evidence is a crucial underpinning of clinical practice. Nevertheless, the first series of articles aimed at providing clinicians with guidelines for critically appraising the evidence that informs clinical practices did not appear until 1981.¹ Ten years later, the term “evidence-based medicine”² first appeared in the medical literature. Subsequently, between 1993 and 2000, a group of evidence-based medicine enthusiasts³ published a series of 25 articles aimed at assisting clinicians in understanding and applying the medical literature to their clinical decision-making in a clinical setting.⁴

The concept of evidence-based medicine soon expanded to other clinical areas. The first article to use the term “evidence-based dentistry” (EBD) was published in 1995 by Richards and Lawrence,⁵ and since then other articles have been published on the topic.^6–11 There is, however, still no guide easily accessible for current and future dental practitioners that addresses the critical appraisal and use of evidence specifically aimed at clinicians and educators in oral health care fields.

This book aims to provide an overview of the basic concepts of EBD to assist oral health care professionals in making use of evidence to inform their clinical decisions. This book addresses the main topics in EBD, including how to formulate questions that are easy to answer using the scientific literature, effectively search for relevant evidence, identify the strengths and limitations of different study designs and interpret their findings, and apply findings to clinical decisions. Although this book mostly focuses on the application of research to clinical practice, it also provides a perspective at the health policy level.

Definition and Principles of EBD

The American Dental Association defines EBD as “an approach to oral healthcare 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.”¹² The definition of EBD has three main components:

Figure 1.1. The Components of Evidence-Based Dentistry

One definition of evidence is “any empirical observation whether systematically collected or not.”¹⁴ Evidence can be obtained from a range of sources, including clinical observation of the course of a single patient or a multicenter and multinational clinical study. Evidence to inform any clinical decision is abundant. However, as some evidence is more trustworthy than other evidence, it is both necessary and desirable to prioritize certain types of evidence.

Because unsystematic clinical observations of a small number of patients are more likely to introduce more bias than are appropriately designed and conducted clinical studies, for example, astute clinicians always should prefer the latter evidence to the former.¹⁴ For each type of clinical question, there is a hierarchy of evidence that is based on degree of trustworthiness. For instance, to answer questions regarding the effectiveness of a particular intervention, the strongest evidence would come from randomized clinical trials with a low risk of bias and large sample sizes, as such evidence provides more precise estimates and more consistent results and is directly applicable to the patients at hand. If findings from such studies are not available for the specific question of interest, clinicians must rely on less trustworthy evidence, including well-designed and conducted observational studies, such as cohort and case-control studies. If no randomized trials, cohort and case-control studies, or case series/case reports are available, individual observations by a clinical expert may become a valuable source of evidence. In subsequent chapters, we discuss the hierarchy of evidence for each type of clinical question (that is, therapy and prevention, harm, prognosis, and diagnosis) and how to appraise the relevant literature critically.

As stated above, evidence alone is not enough to support clinical decision-making from an EBD perspective; decision-making should rely on the integration of evidence with clinical expertise and patients’ needs and preferences. The success of an intervention that has proven to be effective in a clinical study depends on the ability of a clinician to use the intervention in an appropriate clinical setting. In other words, clinical expertise is key to determining whether and how the evidence can be applied to a specific patient’s case.¹⁴ Finally, because clinical procedures are associated with potential adverse effects, including the burden of the procedure and its costs, it is important to consider patients’ values and preferences when making a decision regarding treatment.

The Process of EBD

The decisions clinicians must make in daily clinical practice are the most important source of questions for which we seek evidence-based solutions. Such questions constitute the starting point of the EBD process, which encompasses the following main steps:

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