MORE ABOUT TOOTH WHITENING
We are writing with comments about the February JADA cover story, "Light Augments Tooth Whitening With Peroxide," by Dr. J. Max Goodson and colleagues. We were very surprised that JADA would publish an article that is so devoid of scientific validation or explanation. We believe that the findings reported in this study are highly suspect, and certainly are not as conclusive as the authors suggest. This is most unfortunate, because the results of this study already have been reported not only to the dental profession, but also to the general public through media, including television health segments.
We offer the following specific comments:
- – The authors state that "power bleaching" is accomplished in a single office visit. In fact, most clinicians have found that multiple appointments are required to achieve significant whitening. Previous research1 has demonstrated that the most important factor is the concentration of the bleach, not the use of a light. The Papathanasiou study reported that the addition of light is of no use in bleaching whatsoever.
- – Although not a peer-reviewed publication, it is interesting to note that similar results were reported in the CRA Newsletter from April 2000.2 The results of a split-arch study using light and bleach versus beach alone revealed that light has no effect on the bleaching results. Even considering that 15 percent hydrogen peroxide clearly has the capacity to whiten teeth, the degree of whitening reported in the JADA article far exceeds that which can be reasonably expected from such a short-term treatment duration.
- – Multiple examiners were involved in conducting the study, but apparently not in making the shade evaluations. The article notes that "the same investigator conducted all shade guide color evaluations... ." In contrast, most clinical trials of bleaching involve two evaluators, both of whom have been calibrated. Bleaching studies of this type should use two calibrated evaluators for increased reliability and validity, and calibration should be conducted pre- and post-study to ensure inter- and intra-rater reliability. When using two evaluators, a consensus is obtained for each case, which is far more reliable than the independent assessment of one evaluator, who can be inherently biased, whether intentionally or not. No mention of calibration, even for the one evaluator, was made in this article.
- – There is no description of whether or how the colorimeter was calibrated.
- – The authors state that re-application of the "hydrogel" prevented teeth from drying out during treatment. However, the composition of this hydrogel is not described in the article whatsoever. Prevention of dehydration with any in-office bleaching procedure is virtually impossible, regardless of the composition of the whitener. And yet this article totally ignores the role of dehydration in the whitening process, even when it is widely known that dehydration effects result in considerable—but temporary—whitening effects that can exceed the immediate whitening effects of the bleach itself.
- – It also is very puzzling that no recall assessments were made following rehydration of the teeth until three and six months after treatment. A one-week or one-month assessment would have been appropriate. Immediate posttreatment evaluations of shade changes have limited value because of the very important covariable of dehydration, which itself can account for substantial whitening effects.
- – Figures 4 and 5 report Vita shade guide changes of 13 and nine shade units, respectively. Admittedly, the color reproduction might be imperfect (although tissue tones appear equal), but neither case appears to reflect changes of these magnitudes.
- – The subjective Vita shade data generally are far more impressive than the colorimeter data, which raises further questions about the accuracy of the Vita shades. For example, at six months, the light reportedly provided an improvement of four Vita shades. However, the colorimeter data indicate
L* = 0.33 and b* = –0.45. These are very small changes, and cannot explain a true Vita shade improvement of four. Rather, they suggest the possibility of evaluator bias in the Vita shade selections.
- – The statistical analysis appears quite impressive. However, if the data are inherently erroneous from evaluator bias or are otherwise flawed, no statistical analysis can render valid results. Moreover, it is unclear whether the statistical analysis considered each tooth or each subject (patient) as an individual case. Figure 2 certainly implies that individual teeth were used. Using teeth instead of subjects increases the sample size fourfold and clearly would impact the statistical analysis.
- – Many of the results in this study are quite remarkable, yet little explanation is offered in the Discussion section. For example, the evaluator’s assessment that revealed lighter teeth at three and six months for the "light only" group is very remarkable, yet the author fails to adequately address why—or more importantly how—long-term whitening from one treatment exposure to the light could have occurred. This observation is indeed quite remarkable and historically unprecedented. Surely some scientific explanation, theoretical or not, is warranted.
- – Similarly remarkable results relate to the significantly improved gingival indices for all treatment groups at three and six months following only one treatment session. How can a short exposure to a light have any therapeutic benefit on gingival health? This observation, too, is astounding. Again, surely such an important finding deserves some attempt at a scientific explanation.
- – The authors attempt to relate the improved gingival health noted in the groups exposed to the peroxide as being similar to those results noted in the literature (references 24 through 26). However, these references are totally inappropriate to explain the results observed in this study, because those studies dealt with carbamide peroxide whiteners, which contain urea, which has been shown to provide significant antiplaque effects.
- – The gingival index results could be explained as either a statistical anomaly or a result of the Hawthorne effect (a distortion of research results caused by the response of subjects to the special attention they receive from researchers). The simple fact that these subjects participated in a clinical trial could have affected their oral hygiene habits.
- – The entire Discussion section is, in our opinion, superficial and highly biased in its tenor, and does not attempt to delve into the literature to explain why the noted results occurred. It provides little in the way of a credible scientific explanation for the observed results. Even the title of the article sounds like a news headline, rather than the title of a scientific investigation.
In conclusion, we find it unfortunate that JADA saw fit to publish, and highlight on the cover, an article with so many inherent problems and unsubstantiated claims, especially when the topic is of such obvious interest to the profession and the public. A journal that is supposed to be the flagship publication for dentistry has a responsibility to ensure that only articles of sufficient scientific merit and validity are published within its pages.
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REFERENCES
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- Papathanasiou A, Kastali S, Perry RD, Kugel G. Clinical evaluation of a 35% hydrogen peroxide in-office whitening system. Compend Contin Educ Dent 2002;23(4): 335–46.[Medline]
- CRA Newsletter. Vital tooth bleaching, in-office. April 2000;24(4):1–3.
Edward J. Swift Jr., D.M.D., M.S., Professor and Chair and
Harald O. Heymann, D.D.S., M.Ed., Professor and Graduate Program Director
Department of Operative Dentistry, University of North Carolina, Chapel Hill
Gerard Kugel, D.M.D., M.S., Associate Dean for Research, Professor of Restorative Dentistry
Tufts University Boston
John Kanca III, D.M.D., Private practice
Middlebury, Conn.
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