Evidence-based practice and the evidence pyramid: A 21st century orthodontic odyssey

Organized evidence-based practice is said to have started in the medical field in the late 20th century. Its principles and usage eventually spread to other health sciences, including orthodontics. Although the conceptual foundations and basic tenets of evidence-based orthodontics are based on the classical approach of testing medical interventions, differences unravel as we encounter the ground realities in orthodontics, which are unique due to the length, complexity, and diversity involved in orthodontic treatment and research. How has this led to the evolution of evidence-based orthodontics and changes in its applications? Is it being translated to better clinical answers, treatment strategies, patient satisfaction, and information for orthodontists? What more needs to be done, considering the rapidly changing orthodontic scenario? This article aims to explore these questions to evaluate how evidence-based orthodontics has played itself out so far, so that it can continue to grow strong and stand up to the challenges of 21st century orthodontics.

Highlights

  • Evolution of evidence-based practice in response to unique issues in Orthodontics is a necessity.

  • Classical evidence pyramid variants, may provide solutions relevant to the field of Orthodontics.

  • Quality refinement and standardization of primary research will strengthen evidence base.

  • Pre-appraised, easily accessible formats of evidence enhance usability and clinical application.

  • Symbiotic “evidence” and “expert” aligned with patients’ values or preference ensure best care.

Dentistry as a profession has evolved through the ages of the expert, professionalism, and science and brought us currently into the age of evidence. Evidence-based orthodontics (EBO) is considered to be an important contributor to the rapidly changing scenario of orthodontic practice in the 21st century. Over the past 2 to 3 decades since its inception, concerted efforts have been made to implement EBO and change the perception and practice of orthodontics from just an art to an art and a science grounded in scientific foundations able to withstand the tests of scientific rigor and scrutiny. From exhortations in leading orthodontic journals, creating awareness through specialty conferences and meetings by professionals and orthodontic societies, to inculcating it into orthodontic education and training, all have played an important role. EBO is still in its early stages, and the evolution, development, and organization of the orthodontic evidence base is constantly being shaped and redefined by challenges of clinical applications and practical issues, an overview of which is provided in this article by following the trajectory of EBO from its origins to its most recent developments.

Genesis of EBO and the evidence pyramid

Evidence-based practice emerged as an alternative to “expert-based,” “eminence-based,” or “opinion-based” orthodontics. Its modern day origin can be traced to the medical field, where the urgent need for testing efficacy, safety, and suitability of drugs for clinical application and formalizing rules for grading quality of evidence arose consequent to medical disasters such as the thalidomide tragedy and deaths from the application of untested procedures, products, or hypotheses in clinical practice. As evidence-based medicine started gaining popularity in the 1980s, its principles spread to dentistry and orthodontics. The term “evidence-based dentistry” was first used in the article by Richards and Lawrence in 1995. Although the first randomized controlled trial (RCT) in orthodontics on Class II malocclusion was reported by Jakobsson in 1967, the beginning of the evidence-based orthodontic era is mostly associated with the National Institute of Dental and Craniofacial Research funding trials on the same topic in the late 1980s.

A fundamental tool for evidence-based practice has been the evidence pyramid, which depicts the hierarchy or levels of evidence from lowest to highest ( Fig 1 ). The levels of evidence were originally described by the Canadian Task Force on the Periodic Health Examination in 1979 to develop recommendations based on evidence in the medical literature. Sackett developed these further into the evidence pyramid. Levels of evidence are arranged in increasing order of internal validity (rigor or freedom from bias) from bottom to top, with in-vitro and animal studies placed at the lowest level, followed by opinions, case reports, observational studies, RCTs, systematic reviews, and meta-analyses at the tip, representing the highest level of available evidence ( Fig 1 ).

Fig 1
The pyramid of evidence: systematic reviews, meta analyses, RCTs. SR , Systematic reviews; MA , meta-analyses.

Evidence pyramid: beyond traditional hierarchy

The evidence pyramid with its origin in evidence-based medicine gives the highest importance to the RCT study design as the best method to generate reliable and unbiased evidence. The discrete and well-delineated axis of disease-pathogenic agent / process-pharmacologic intervention in medicine lends itself well to the RCT study design. However, in orthodontics, the etiology of malocclusion is complex and multifactorial; treatment modalities are multiple, appliance-driven, and operator-dependent; and treatment effects are simultaneous, cumulative, and gradual. These create concerns of complexity, ethics, length of time required to complete orthodontic treatment, posttreatment follow-up, impracticality, and cost. Hence, it is not possible to conduct RCTs for all questions in orthodontics. This has led to the exploration of more pragmatic models; one of them is the “hierarchy of quality in the evidence for clinical outcomes in orthodontics” of Proffit ( Fig 2 ), which departs from the traditional hierarchy in 2 important ways: by giving greater recognition and weight to good retrospective or nonrandom prospective studies, and by questioning the validity of poorly conducted systematic reviews.

Fig 2
Hierarchy of quality in the evidence for clinical outcomes in orthodontics.
Reproduced with permission.

Evidence pyramid: beyond traditional hierarchy

The evidence pyramid with its origin in evidence-based medicine gives the highest importance to the RCT study design as the best method to generate reliable and unbiased evidence. The discrete and well-delineated axis of disease-pathogenic agent / process-pharmacologic intervention in medicine lends itself well to the RCT study design. However, in orthodontics, the etiology of malocclusion is complex and multifactorial; treatment modalities are multiple, appliance-driven, and operator-dependent; and treatment effects are simultaneous, cumulative, and gradual. These create concerns of complexity, ethics, length of time required to complete orthodontic treatment, posttreatment follow-up, impracticality, and cost. Hence, it is not possible to conduct RCTs for all questions in orthodontics. This has led to the exploration of more pragmatic models; one of them is the “hierarchy of quality in the evidence for clinical outcomes in orthodontics” of Proffit ( Fig 2 ), which departs from the traditional hierarchy in 2 important ways: by giving greater recognition and weight to good retrospective or nonrandom prospective studies, and by questioning the validity of poorly conducted systematic reviews.

Fig 2
Hierarchy of quality in the evidence for clinical outcomes in orthodontics.
Reproduced with permission.

Consideration of nonrandom study designs

Calls for integrating evidence from study designs other than RCTs and reducing overemphasis on RCTs have been made in literature by Bondemark and Ruf, Meikle, Johnston, Baumrind, and Ionnaidis et al. Indiscriminate inclusion of nonrandom study designs increases uncertainty and decreases confidence in the resulting evidence. Hence, for nonrandom study designs to be considered as sources of reliable evidence, they need to fulfil the 3 criteria for good quality studies: (1) have well-defined patient groups with selection based on pretreatment characteristics and receiving specific treatments, rather than a variety of treatments; (2) account for all patients included in the study for analysis and reporting and not just the successful ones; and (3) use appropriate methodology and statistics.

As the extraction-nonextraction pendulum has swung in orthodontic history, it seems so is the randomized-nonrandomized studies pendulum swinging in the present. RCTs and nonrandomized or retrospective studies are not to be viewed as mutually exclusive, incompatible, or invalidating of each other. Studies at every level engender their own utility and contribute to scientific knowledge, either by guiding further studies at higher levels or by providing evidence that higher-level studies failed to generate. Voudouris highlighted the importance of in-vitro studies in orthodontics, suggesting that they be placed above expert opinion in the proposed modified pyramid called “iceberg of evidence,” in which the clinical application represented as the visible tip of the iceberg is supported by the submerged inverted pyramid of “academic findings” ( Fig 3 ). The broadest and topmost levels of the submerged part are assigned to systematic reviews, meta-analyses, and RCTs followed by less rigorous study designs that progressively taper toward the bottom and farther from the clinical application zone. Orthodontic products are straightaway released commercially unlike medical products that are mandated by strict regulatory guidelines to demonstrate efficacy and safety standards before being released for public use. Hence, the importance attributed to orthodontic in-vitro studies to investigate biologic interactions, properties, behavior, and safety of biomaterials.

Fig 3
Iceberg of evidence for viable clinical applications.
Reproduced with permission.

Walach et al proposed the “circle of methods” as an alternative to the hierarchy model, where evidence from every study design is used to counterbalance the strengths and weaknesses of individual studies and generate evidence that is closer to the realities of clinical applications as opposed to the strictly controlled environment of an RCT ( Fig 4 ). Thus, the upper half of the circle is represented by the experimental method (RCTs) to test efficacy; these studies are then complemented by observational, nonexperimental methods (lower half of the circle) that are more descriptive and somewhat reflect real-life effects and applicability, such as retrospective audits and prospective studies. However, Ionnaidis et al cautioned that although using nonrandomized studies may be justified in certain situations, these alternative approaches should not be misused to bypass the requirement of scientific rigor in evidence-based practice and undermine the efforts to promote RCTs, so as to obtain easy answers from nonrandomized designs. RCTs should be the first choice wherever it is feasible to conduct them.

Fig 4
Circle of methods for generating evidence.
Reproduced with permission.

Technology usage and digitization have brought us the current hot topic of “big data” analysis in health research. Also known as “data mining,” it refers to the analysis of patient data recorded in electronic databases of practices, institutions, or companies. One such example is a study where a retrospective analysis of more than 5000 patients was done using an electronic health records system; the authors found no relationship between obstructive sleep apnea and premolar extractions. By providing data that enormously exceed traditionally available resources, big data appears promising. However, its pitfalls include the possibility of generating false-positive results consequent to multiple comparisons and launching “fishing expeditions” to explore data without biologically plausible underlying theoretical models that may give rise to misleading results. Contributions from big data analysis to the traditional evidence base may well be a future trend in orthodontic research, but as it is usually with newer methods, it must be tried, tested, critically evaluated, and appropriately applied.

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Dec 19, 2018 | Posted by in Orthodontics | Comments Off on Evidence-based practice and the evidence pyramid: A 21st century orthodontic odyssey
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