Critical Thinking

Understanding and Evaluating Dental Research, Third Edition

Donald Maxwell Brunette

• Publisher: Quintessence Publishing Co, Inc
• Year: 2020
• ISBN:
  9780867158014
• Edition: 3
• Topic: Medicine
• Subtopic: Dentistry

The Internet has given us access to an unprecedented amount of information, but this development also facilitates the spread of misinformation if we do not think critically and evaluate what we read. The third edition of this classic textbook has been revised based on developments in biomedical research practices over the past decade to provide readers with the most up-to-date resource for navigating the ever-expanding world of dental literature. The book covers rhetoric and logic, the scientific method, components of scientific papers, research strategies, probability and statistics, diagnostic tools and testing, and experiment design. The chapter about searching the dental literature has been updated with the most current resources and search techniques available. A new chapter about clinical decision making uses a decision tree analysis with worked-out calculations to show how critical thinking skills can be used to select the most appropriate treatment decision in a clinical scenario; this is followed by a whole chapter of exercises in critical thinking. This book emphasizes how readers can practically apply critical thinking skills to evaluate scientific literature and thereby make the most informed decisions for their patients and themselves.

1

Reasons for Studying Critical Thinking

“

It has happened more than once that I found it necessary to say of one or another eminent colleague, ‘He is a very busy man and half of what he publishes is true but I don’t know which half.’”

ERWIN CHARGAFF1

Critical Thinking

Critical thinking has been defined many ways, from the simple—“Critical thinking is deciding rationally what to or what not to believe”2—to the more detailed “Critical thinking is concerned with reason, intellectual honesty, and open-mindedness, as opposed to emotionalism, intellectual laziness, and closed-mindedness”3—to the nearly comprehensive:

Critical thinking involves following evidence where it leads; considering all possibilities; relying on reason rather than emotion; being precise; considering a variety of possible viewpoints and explanations; weighing the effects of motives and biases; being concerned more with finding the truth than with being right; not rejecting unpopular views out of hand; being aware of one’s own prejudices and biases; and not allowing them to sway one’s judgment.3

Self-described practitioners of critical thinking range from doctrinaire postmodernists who view the logic of science with its “grand narratives” as inherently subordinating4 to market-driven dentists contemplating the purchase of a digital impression scanner. In this book, critical thinking, and in particular the evaluation of scientific information, is conceived as “organized common sense” following Bronowski’s view of science in general.5 Of course, common sense can be quite uncommon. A secondary use of the term critical thinking implies that common sense involves a set of unexamined and erroneous assumptions. For example, prior to Galileo, everyone “knew” that heavy objects fell faster than lighter ones. Critical thinking as organized common sense takes the systematic approach of examining assumptions. The professional use of critical thinking is particularly complex for dental professionals because they live in two different worlds. On the one hand, they are health professionals treating patients who suffer from oral diseases. On the other hand, dentists typically also inhabit the business world, where decisions may be based on the principle of maximizing income from their investment. Dental practice is based only very loosely on responding to disease6; less than one-third of patient visits result in identifying a need for restorative care.7 Twenty percent of work is elective, such as most of orthodontics, tooth whitening, and veneers, and typically that work comprises the most lucrative aspects of practice. Thus, the information that must be evaluated in performing these disparate roles covers the spectrum from advertisements to financial reports to systematic meta-analysis of health research.

Dentists are health professionals, people with specialized training in the delivery of scientifically sound health services. The undergraduate dental curriculum is designed to give dental students the basic knowledge to practice dentistry scientifically, at least to the extent allowed by the current state of knowledge. But if any guarantee can be made to dental students, it is that dentistry will change, because the knowledge base of biomedical and biomaterial sciences grows continually. Most dentists today have had to learn techniques and principles that were not yet known when they were in dental school. In the future, as the pace of technologic innovation continues to increase and the pattern of dental diseases shifts, the need to keep up-to-date will be even more pressing. Means of staying current include interacting with colleagues, reading the dental literature, and attending continuing education courses—activities that require dentists to evaluate information. Yet, there is abundant historical evidence that dentists have not properly evaluated information. Perhaps the best documented example in dentistry of a widely accepted yet erroneous hypothesis is the focal infection theory. Proposed in 1904 and accepted by some clinicians until the Second World War, this untested theory resulted in the extraction of millions of sound teeth.8 But errors are not restricted to the past; controversial topics exist in dentistry today because new products or techniques are continually introduced and their usefulness debated. Ideally, dentists should become sophisticated consumers of research who can distinguish between good and bad research and know when to suspend judgment. This goal is different from proposing that dentists become research workers. One objective of this book is to provide the skills enabling a systematic method for the evaluation of scientific papers and presentations.

A marked addition to the challenges of dental practice in recent years is that patients have increased access through the Internet to information as well as misinformation. Dentists thus are more likely to be questioned by patients on proposed treatment plans and options. In responding to such questions, it is clearly advantageous for dentists to be able to present a rational basis for their choices. Chapter 23 covers an evidence-based approach to clinical decision making and appendix 9 provides a template for dental offices to use in documenting their decisions based on recent evidence.

A systematic approach to analyzing scientific papers has to be studied, because this activity requires more rigor than the reasoning used in everyday life. Faced with an overabundance of information and limited time, most of us adopt what is called a make-sense epistemology. The truth test of this epistemology or theory of knowledge is whether propositions make superficial sense.9 This approach minimizes the cognitive load and often works well for day-to-day short-term decision making. In 1949, Zipf of Harvard University published Human Behaviour and the Principle of Least Effort, in which he stated:

The Principle of Least Effort means, for example, that in solving his immediate problems he will view these against a background of his probable future problems, as estimated by himself. Moreover, he will strive to solve his problems in such a way as to minimize the total work that he must expend in solving both his immediate problems and his probable future problems.10

Zipf used data from diverse sources ranging from word frequencies to sensory sampling to support his thesis. Although the methods and style of psychologic research have changed, some more recent discoveries, such as the concept of cognitive miser in studies of persuasion,11 coincide with Zipf’s principle. Kahneman in Thinking, Fast and Slow has elevated the principle to a law noting that we “conduct our mental lives by the law of least effort.”12

In science, the objective is not to make easy short-term decisions but rather to explain the phenomena of the physical world. The goal is accuracy, not necessarily speed, and different, more sophisticated, more rigorous approaches are required. Perkins et al9 have characterized the ideal skilled reasoner as a critical epistemologist who can challenge and elaborate hypothetical models. Where the makes-sense epistemologist or naive reasoner asks only that a given explanation or model makes intuitive sense, the critical epistemologist moves beyond that stage and asks why a model may be inadequate. That is, when evaluating and explaining, the critical epistemologist asks both why and why not a postulated model may work. The critical epistemologist arrives at models of reality, using practical tactics and skills and drawing upon a large repertoire of logical and heuristic methods.9

Table 1-1 | Level of evidence guideline recommendations of the United States Agency for Healthcare Research and Quality

Level	Type of study	Grade of recommendation
1	Supportive evidence from well-conducted RCTs that include 100 patients or more	A
2	Supportive evidence from well-conducted RCTs that include fewer than 100 patients	A
3	Supportive evidence from well-conducted cohort studies	A
4	Supportive evidence from well-conducted case-control studies	B
5	Supportive evidence from poorly controlled or uncontrolled studies	B
6	Conflicting evidence with the weight of evidence supporting the recommendation	B
7	Expert opinion	C

RCTs, randomized controlled trials.

Psychologic studies have indicated that everyday cognition comprises two sets of mental processes, System 1 and System 2, which work in concert, but there is some debate whether they operate in a parallel or sequential manner. System 1 operates quickly and effortlessly, whereas System 2 is deliberate and requires attention and effort.12 System 2 is a rule-based system, and engaging System 2 is the surest route to fallacy-free reasoning.13 System 2 becomes engaged when it catches an error made by the intuitive System 1. The good news is that extensive work by Nisbett and colleagues (briefly reviewed by Risen and Gilovich13) showed that people can be trained to be better reasoners and that people with statistical backgrounds were less likely to commit logical fallacies. Nisbitt and colleagues further demonstrated that even very brief training was effective in substantially reducing logical and statistical errors. Thus this book has chapters on logic and statistics.

A second objective of the book is to inculcate the habits of thought of the critical epistemologist in readers concerned with dental science and clinical dentistry.

The scope of the problem

In brief, the problems facing anyone wishing to keep up with developments in dentistry or other health professions are that (1) there is a huge amount of literature, (2) it is growing fast, (3) much of it is useless in terms of influencing future research (less than 25% of all papers will be cited 10 times in all eternity,14 and a large number are never cited at all), and (4) a good deal of the research on a clinical problem may be irrelevant to a particular patient’s complaint

The actual rate of growth of the scientific literature has been estimated to be 7% per year of the extant literature, which in 1976 comprised close to 7.5 million items.11 This rate of growth means that the biomedical literature doubles every 10 years. In dentistry, there are about 500 journals available today.15 Many dental articles are found in low-impact journals, but, ignoring these, there were still 2,401 articles published in 1980 in the 30 core journals.16 More recently, it has been estimated that about 43,000 dental-related articles are published per year.

However, the problem is not intractable. Relman,17 a former editor of the New England Journal of Medicine, believes that most of the important business of scientific communication in medicine is conducted in a very small sector of top-quality journals. The average practitioner needs to read only a few well-chosen periodicals.17 The ke...

Table of contents

• Cover
• About the Book
• Half Title Page
• Title Page
• Copyright Page
• Table of Contents
• Dedication
• Preface
• 1 Reasons for Studying Critical Thinking
• 2 Scientific Method and the Behavior of Scientists
• 3 The Components of a Scientific Paper
• 4 Rhetoric
• 5 Searching the Dental Literature: with Helen L. Brown
• 6 Logic: The Basics
• 7 Introduction to Abductive and Inductive Logic: Analogy, Models, and Authority
• 8 Causation
• 9 Quacks, Cranks, and Abuses of Logic
• 10 Elements of Probability and Statistics, Part 1: Discrete Variables
• 11 Elements of Probability and Statistics, Part 2: Continuous Variables
• 12 The Importance of Measurement in Dentistry
• 13 Errors of Measurement
• 14 Presentation of Results
• 15 Diagnostic Tools and Testing: with Ben Balevi
• 16 Research Strategies and Threats to Validity
• 17 Observation
• 18 Correlation and Association
• 19 Experimentation
• 20 Experiment Design
• 21 Statistics As an Inductive Argument and Other Statistical Concepts
• 22 Judgment
• 23 Introduction to Clinical Decision Making: with Ben Balevi
• 24 Exercises in Critical Thinking
• Appendices
• Index
• About the Contributors
• Backcover