I appreciate Dr. Overton taking the time to critique my comments, and I respect his views. I welcome the comments of readers, and often agree with them. However, this letter has stimulated a few comments of my own relative to "in vivo" research, "in vitro" research, clinical observation and the state of so-called "evidence-based" research.
Rather than addressing in detail each of the critiques of my column expressed by Dr. Overton, I will provide an overview of a much more important issue he stimulated.
It has been 41 years since I, too, was "Head of Operative Dentistry" for the first time, and much has happened to mellow my acceptance of in vitro research projects and semiclinical in vivo projects that are conducted in a manner not related to the required speed of actual clinical practice. Many years ago, while attempting to climb the academic ladder with publications, I was engrossed with simply and rapidly accomplishing in vitro research, and I was generally impressed with my ability to "prove" the apparent reliability of concepts and techniques through laboratory research and clinical studies, accomplished at a meticulous and nonclinically practical pace.
Later, after attending two graduate schools, conducting many research projects and receiving a receiving a significant statistical education (I actually taught statistics for a while), I found I could "prove" almost anything by manipulating the research protocol in the right way and adapting the most lenient statistical programs to the data. I could probably relate the color of socks you wear to be statistically significant to the length of your finger. I then taught scientific method and writing, and had to select projects out of the literature for critique. A couple of the hundreds of classic examples of misleading research are:
Circa 1975: The in vitro two-and three-phase wear studies in the scientific literature repeatedly showed that Adaptic (Johnson & Johnson Personal Products; Skillman, N.J.), a large filler particle size resin-based composite, had superior wear characteristics to the product Isopast (Ivoclar Vivadent; Amherst, N.Y.), a then new silicon-dioxide filled microfill. A large-scale clinical in vivo project we at Clinical Research Associates (CRA) and then many others accomplished showed the reverse when observed in the mouth—microfills wore less. In other words, the "scientific" statistically significant literature presented in vitro data that was diametrically opposed to what really happened and what clinicians observed.
Circa 1979–1990: The in vitro scientific literature showed that polycarboxylate cements had far better physical properties than the then commonly used zinc phosphate cement. Unsuspecting clinicians, trusting the "scientific literature," changed to polycarboxylate. Seven to 10 years later, many of the polycarboxylate-cemented restorations "fell off." Again, in vitro data misled thousands of practitioners.
Now, let’s move to present time. Every project in our research group, CRA, undergoes careful basic science research, followed by "real world" use and critique by clinical practicing dentists. Our own in vitro data show that several current dentin-bonding agents have mature, thermally cycled bonds to dentin ranging from 30 to 50 megapascals, while the respective enamel bonds with the same materials are only 20 to 30 MPa.
If I believed our own in vitro data to be clinically significant, I would say dentin bonds are stronger than enamel bonds. How wrong I would be! Any experienced clinician who has cut off a ceramic veneer bonded to enamel knows he or she cannot get it off without cutting it from the enamel. The same clinician cutting a veneer from a dentin surface finds the moment the rotary instrument touches the tooth, the veneer flips off. In other words, again the "scientific, in vitro" research, including our own, would mislead me.
My candid opinions at this time about judging whether research reported in the literature should be applied to evidence-based practice are as follows:
- – In vitro research provides interesting and occasionally clinically applicable data, but anyone relying on it for guidance in clinical practice must be widely read and clinically experienced enough to interpret it. Additionally, in vitro research must be backed up with clinical data in order to have any practical value.
- – In vivo research is useful only if the investigators are clinically competent in a pragmatic manner, knowledgeable about popular clinical techniques and able to relate their clinical procedures to adequate practice management concepts. In my opinion, clinical research accomplished at a slow, nonfinancially practical level is of academic interest only, and is often misleading to practitioners.
- – In vitro or in vivo research funded by companies or individuals with vested financial interests is often justifiably highly suspect and must be backed up with independently funded, clinically relevant, financially practical research. Unfortunately, we often see such biased research published in "peer-reviewed" journals.
In my opinion, some of the most reliable and useful clinical research in dentistry over the past half-century has come from clinical study clubs with clinically competent, research-oriented members who can document actual clinical success or failure with statistical support.
After nearly five decades of teaching, research and practice in dentistry, I am often appalled at some of the nonsense published in the dental literature and its minimal value to the profession. Such reports only illustrate the lack of clinical knowledge and actual long-term clinical experience of the investigators.
To sum up this tirade Dr. Overton stimulated: true, reliable, evidence-based research must have independently funded, multisource, preferably long-term clinical research; some in vitro research to predict or interpret clinical findings; and assurance that the investigators are honest, competent, nonbiased and nonfinancially oriented. Unfortunately, precious few such studies exist in the literature.
Ask any observant practicing dentist to respond to Dr. Overton’s comments about my column. To state an old adage, "The proof is in the pudding."
"Clinical success is the final test" is a statement on every CRA Newsletter. Dr. Overton’s statements about some of my "observations" in the recent column on bonding need significant observation and comment from real-world practicing dentists, not a smattering of miscellaneous "data" that anyone can find on PubMed.
I welcome the chance to discuss Dr. Overton’s specific beliefs and questions with him, and to compare them with both clinical and laboratory research and, more importantly, to discuss how clinical observations verify or refute the "literature." Evidence-based dentistry requires mature interpretation of apparent or alleged truths. Often, investigators have good intentions, but lack the pragmatic clinical judgment to interpret their findings.
