Dr. Gary Greenstein’s landmark article ("Clinical Versus Statistical Significance as They Relate to the Efficacy of Periodontal Therapy," May JADA) raised important points regarding the clinical significance of the statistically significant comparisons used by practitioners, dental manufacturers, insurance providers and others to underpin novel treatment regimens.
His discussion of "numbers needed to treat" and "numbers needed to harm" highlights important concepts in light of the intensive marketing efforts that often accompany products that can produce statistically significant improvements in clinical variables, but which will produce clinically significant results only occasionally.
Drugs and devices approved by the U.S. Food and Drug Administration all have appropriate uses. However, few are best for all situations. Not surprising, salespersons tout the purported benefits of new treatment paradigms that feature their product(s), but seldom raise—or even know—the range of costs that can result from the widespread adoption of the therapeutic algorithms they promote.
(In this context, costs include the obvious—namely the money paid—but also may include the physical, psychological and additional financial costs to a patient for whom appropriate therapy or referral to a specialist is delayed or denied.) It is both unfortunate and avoidable that such costs are often borne by patients with periodontitis.
That said, Dr. Greenstein’s suggestion that the statistical power for clinical trials should be computed using a "clinically significant change" in outcomes (for example, 2 millimeters of attachment gain in a periodontal regeneration study) is too restrictive. It would unduly curtail advances in therapeutics. Clinical significance is in the eye of the beholder!
Indeed, it must be this way because practitioners don’t treat the "average" patient or site—rather, they treat individuals. The best solution to the significance conundrum discussed by Dr. Greenstein is for the beholder (us) to be better able to separate marketplace hype from clinical realities.
That’s what the public expects and deserves from dental professionals—and is partly why Dr. Greenstein’s contributions to the biomedical literature are so important.
