Evidence-Based Dentistry in a Nutshell

This summary is based on information found in Comprehensive Preventive Dentistry (Wiley Publishing, 2013)

• “Evidence-based health care takes place when decisions that affect the care of patients are taken with due weight accorded to all valid, relevant information” (Hicks 2011).
• To understand the concepts of evidence-based dentistry, it is important to understand the basis of epidemiology, the nature of a given research question, and the best study designs that would provide the evidence to such a question.

Epidemiology

• The study of the frequency, distribution, and determinants of health conditions or events (including disease) in human populations and the application of such study to control diseases and other health problems (U.S. Department of Health and Human Services 2006).
• Oral epidemiology: studies oral health and disease through its central concern with causation and the relationships among various exposures or interventions and their outcomes.

Epidemiology Process

1. Observation: An initial observation of the distribution of a disease in a population leads to the suspicion that a given factor influences the occurrence of disease.
2. Formulation of specific hypotheses: The suspicions concerning influence of a particular factor on disease occurrence is stated as a formal hypothesis, a tentative plausible theory and a supposition that links the onset of disease with some factor in a form that will allow it to be tested and refuted (U.S. Department of Health and Human Services 2006).
3. Conduct study and assess validity of association: A plausible hypothesis is tested by means of an epidemiological study.
4. Make a judgement on causation: An association exists if two variables appear to be related by a mathematical relationship; with a change of one appears to be related to the change in the other in the opposite direction or in the parallel direction.

Study designs in epidemiologic studies and their analytical framework

• Study design is the way in which health status and risk factor data are to be measured and collected and a hypothesis is tested.

Descriptive studies

• Include activities related to characterizing the distribution of diseases within a population. It is the aspect of epidemiology concerned with organizing and summarizing data regarding the persons affected, time, and place (U.S. Department of Health and Human Services 2006).
• Are useful for documenting the health of populations, monitoring trends and planning for public health resources, and formulating hypotheses or showing that there is an association between a given disease and a specific factor that may be related to onset.
  • Descriptive studies: case report: Consists of a detailed profile and report of a health problem by the observant clinician in one single patient, that is, the case.
  • Descriptive studies: case series: A case series is a report of description of individual cases that appear to have what may be a new disease or side effect of treatment.
  • Descriptive studies: cross-sectional surveys: Also known as a frequency survey or a prevalence study is a study at one point of time, in which a sample of persons from a population are enrolled and their exposures and health outcomes are measured simultaneously (US Department of Health and Human Services 2006).
  • Descriptive studies: surveillance: Ongoing systematic collection, analysis, and interpretation of health data that are essential to the planning, implementation, and evaluation of public health practice, closely integrated with the timely dissemination of these data to those who need to know (Centers for Disease Control 1986).
  • Descriptive studies: ecologic studies: Have populations or groups as the unit of analysis. They can therefore measure prevalence and incidence of disease, particularly when disease is rare and can monitor population health so that public health strategies may be developed and directed.

Analytical studies

• Allow us to test hypotheses concerning causal relationships.
• They are concerned with why and how a health problem occurs.
• Comparison groups are used to provide baseline or expected values. So, the associations between exposures and outcomes can be quantified, and hypotheses about the cause of the problem can be tested (US Department of Health and Human Services 2006).
  • Analytical studies: cohort studies: Apply to a well-defined group of people who have something in common when they are first assembled and who are then followed up for a period of time to see what happens to them (US Department of Health and Human Services 2006).
  • Cohort studies proceed in a logical sequence: from exposure to outcome (Grimes and Schulz 2002d).
  • Analytical studies: case control studies: An observational study that enrolls one group of persons with a certain disease, chronic condition, or type of injury (case patients) and a group of persons without the health problem (control subjects) and compares differences in exposures, behaviors, and other characteristics to identify and quantify associations, test hypotheses, and identify causes (US Department of Health and Human Services 2006).

Experimental or interventional studies

• The next step is to produce evidence that allow us to ascertain whether or not various therapeutic or preventive interventions improve a patient’s clinical condition, reduce the frequency of disease in populations, or improve population health.
• The investigator intervenes and then observes the outcomes of that intervention, which for ethical reasons must be one that is believed to do more good than harm.
• Experimental and interventional studies are limited to the assessment of new ways of preventing or treating disease and are usually referred to as clinical trials.

Description of a randomized controlled trial

• A prospective, experimental study that involves primary data generated in the clinical environment.
• Randomized trial is the strongest evidence of the clinical efficacy of preventive and therapeutic procedures in the clinical setting.

Research synthesis

• Reliance on a summative synthesis has gained vast popularity in recent days.
• Informal or narrative review: conducted by experts in the field, most commonly without an explicit question or search methods. Mostly opinion-based, limited in scope, and do not contain critical assessment of quality of the included studies.
• Formal or systematic review (with or without meta-analysis): consists of “a review of a clearly formulated question that uses systematic and explicit methods to identify, select, and critically appraise relevant research, and to collect and analyze data from the studies that are included in the review” (Higgins 2006). Meta-analysis is a statistical technique of combining available data from various studies that are relatively homogeneous and deriving a summary estimate. In the hierarchy of evidence-based health care, a well-conducted systematic review with meta-analysis is considered the highest possible evidence.

Critical appraisal of research: general guidelines

• The purpose of critically reviewing an article is to determine whether the biases inherent in the current study are severe enough that it not only creates doubts about external validity but also doubts internal validity of the study.

Concept of cause and effect in epidemiological studies

• A researcher reports on higher risk of certain exposure in patients who had disease compared to those without disease, how can we conclude that there is a cause and effect relationship between exposure and outcome? In clinical medicine and dentistry, risk factor is mainly used to predict the occurrence of disease.

List of References (PDF)