JADA Continuing Education
Manual versus powered toothbrushes
The Cochrane review
RICHARD NIEDERMAN, D.M.D.
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ABSTRACT
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Background. In a report released in January 2003, The Cochrane Collaboration Oral Health Group provided a systematic review of the effectiveness of powered versus manual toothbrushes, which generated much interest in the popular press.
Methods. The Cochrane researchers developed and implemented search strategies for the Cochrane Oral Health Group’s Trial Register, the Cochrane Central Register of Controlled Trials, MEDLINE and the Cumulative Index to Nursing and Allied Health Literature. They contacted manufacturers for additional information. Trials were selected if they met the following criteria: compared power versus manual toothbrushes, had a randomized design, drew participants from a general population without disabilities, provided data regarding plaque and gingivitis, and were at least 28 days in length. Reviewers evaluated only studies published in 2001 or earlier. Six reviewers from the Cochrane study independently extracted information in duplicate. Indexes for plaque and gingivitis were expressed as standardized values for data distillation. Data distillation was accomplished using a meta-analysis, with a mean difference between powered and manual toothbrushes serving as the measure of effectiveness.
Results. The searches identified 354 trials, only 29 of which met the inclusion criteria. These trials involved about 2,500 subjects and provided data for meta-analysis. The results indicated that only the rotating oscillating toothbrush consistently provided a statistically significant, although modest, clinical benefit over manual toothbrushes in reducing plaque and gingivitis.
Conclusions and Clinical Implications. Some powered toothbrushes with a rotation-oscillation action achieve a significant, but modest, reduction in plaque and gingivitis compared with manual toothbrushes.
The Cochrane Collaboration is an international, volunteer, nonprofit organization. The organization’s focus is to provide peer-reviewed, systematic assessments (based on international standards) of clinical data published in the scientific literature, and to maintain a database of controlled clinical trials. The Cochrane Collaboration is composed of clinicians, journal editors, academicians, industry representatives and patients. The Cochrane Oral Health Group is one of 49 Cochrane Collaboration research groups, with centers in 13 countries. It carries out systematic reviews of oral health–related studies.
Some powered toothbrushes with a rotation-oscillation action achieve a significant, but modest, reduction in plaque and gingivitis compared with manual toothbrushes.
On Jan. 11, 2003, at the Forsyth Conference on Evidence-Based Dentistry, The Cochrane Collaboration’s Oral Health Group presented results of a new systematic review of electric toothbrushes.1 During the following week, reports regarding the electric toothbrush findings appeared in more than 100 media outlets in the United States, United Kingdom, Australia and Asia. The media venues included the Washington Post, Wall Street Journal, Reuters, Newsweek, CNN, National Public Radio, ABC and the British Broadcasting Corporation. This media interest may not be surprising given that 42 percent of U.S. adults and 34 percent of U.S. teenagers view toothbrushes as an invention they cannot live without.2 Furthermore, in the Lemelson-MIT Invention Index Survey,2 toothbrushes were rated more important than automobiles, personal computers, cell phones and microwave ovens.
The importance to the oral health community, however, is that this review implemented internationally accepted, explicit, rules-based methods.3 However, these standards are not in common use yet in the oral health community. The Cochrane Collaboration Oral Health Group’s review of powered versus manual toothbrushes highlights the benefit of adopting international standards for reviewing apparently conflicting clinical data to distill quantitative information for clinical decision making.
In this article, I provide a synopsis of the Cochrane Oral Health Group’s report on powered versus manual toothbrushes, including the study’s methodology and results.
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METHODS
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The Cochrane Collaboration Oral Health Group developed and implemented search strategies to identify all relevant randomized controlled trials, irrespective of language. The following databases were searched by the group: The Cochrane Oral Health Group’s Trial Register, the Cochrane Central Register of Controlled Trials, MEDLINE and the Cumulative Index to Nursing and Allied Health Literature. Manufacturers also were contacted for additional published and unpublished information. Trials were selected based on the following criteria: compared powered versus manual toothbrushes, used a randomized design, tested among the general public without disabilities, were at least 28 days in length and contained data regarding plaque and gingivitis. Trials were excluded if they compared only powered toothbrushes or only manual toothbrushes, were shorter than 28 days, or used a split-mouth design.
The results indicate that there was a wide range in plaque and gingivitis reduction among the powered toothbrushes.
Two reviewers independently assessed the search titles and abstracts that had been identified in the search for studies to be included in the review. If both reviewers agreed that the trial did not meet inclusion criteria, it was considered ineligible. The full text of articles of trials that met the inclusion criteria were then obtained.
A panel of six reviewers from the Cochrane study, in pairs, independently assessed the full-text articles to confirm eligibility. Disagreements were resolved by consensus. The reviewers extracted data from the included articles in duplicate. They expressed indexes for plaque and gingivitis as standardized values for data distillation. They used a meta-analysis (essentially a weighted average) to accomplish data distillation, with a mean difference in plaque or gingivitis index between powered and manual toothbrushes as the primary outcome measure.
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RESULTS
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The database search identified 354 trials, 139 of which were considered ineligible based on review of the title and abstracts. The researchers obtained the full text for 215 articles, 152 of which were considered ineligible. Of the remaining 63 articles, only 29 provided data that were useable for our analysis. These 29 articles presented data from trials conducted in North America, Europe and Israel. As shown in the table
, the authors of the Cochrane review categorized the powered toothbrushes from these studies according to their mode of action.
The researchers grouped the clinical results from all six toothbrush categories according to trial time: short term (one month through three months) and long term (more than three months). The clinical results also were grouped according to outcome measure: plaque and gingivitis. there were four outcomes. I report only the long-term outcomes for plaque and gingivitis, because patients typically expect to see benefits over a six-month period (that is, between dental visits). I should note, however, that the results for both periods were essentially identical.
The results indicate that there was a wide range in plaque and gingivitis reduction among the powered toothbrushes. For plaque reduction, the average mean difference in the plaque index ranged from –0.2 to 1.2 (Figure 1, page 1243). A negative number indicates that, on average, the powered toothbrush was less effective than the manual toothbrush. Conversely, a positive number indicates that the powered toothbrush was more effective than the manual toothbrush. The most effective powered toothbrush in terms of plaque reduction was the rotation-oscillation toothbrush. For this toothbrush, the mean difference of 1.2 converts to a plaque reduction of 7 percent.
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Figure 1. Plaque reduction for powered versus manual toothbrushes. Symbols represent the mean result from multiple clinical trials. Solid symbols indicate that the powered toothbrush was significantly more effective than the manual toothbrush. Open symbols indicate that there was no significant difference between the two types of toothbrushes. Symbols to the right of 0 indicate that the powered toothbrush is more effective than the manual toothbrush. Symbols to the left of 0 indicate that the manual toothbrush is more effective than the powered toothbrush. Horizontal lines indicate the 95 percent confidence interval from multiple clinical trials (a 95 percent confidence interval crossing 0 indicates no statistical difference between powered and manual toothbrushes).1
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For gingivitis reduction, the average mean difference in the gingivitis index ranged from –0.1 to 0.5 (Figure 2, page 1243). As with plaque reduction, a negative number indicates that the manual toothbrush was more effective than the powered toothbrush, while a positive number indicates that the powered toothbrush was more effective. The most effective powered toothbrush for reducing gingivitis was the rotation-oscillation toothbrush. For this toothbrush, the mean difference of 0.5 converts to a gingivitis reduction of 17 percent.
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Figure 2. Gingivitis reduction for powered versus manual toothbrushes. Symbols represent the mean result from multiple clinical trials. Solid symbols indicate that the powered toothbrush was significantly more effective than the manual toothbrush. Open symbols indicate that there was no significant difference between the two types of toothbrushes. Symbols to the right of 0 indicate that the powered toothbrush is more effective than the manual toothbrush. Symbols to the left of 0 indicate that the manual toothbrush is more effective than the powered toothbrush. Horizontal lines indicate the 95 percent confidence interval from multiple clinical trials (a 95 percent confidence interval crossing 0 indicates no statistical difference between powered and manual toothbrushes).1
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Systematic reviews offer the health care community the best quantitative results currently available based on international standards.
Finally, I should note that the data for both plaque and gingivitis reduction in short-term (one through three months) and long-term (more than three months) trials were essentially identical.
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DISCUSSION
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Systematic, rules-based reviews offer several important benefits over traditional narrative reviews (whose scope is typically broad, methods are unstated and study quality is not appraised4). First, systematic reviews offer the health care community the best quantitative results currently available based on international standards. These standards include hypothesis formulation, literature searches, critical appraisal, trial planning, ethical review, trial conduct, trial reporting, systematic reviews and meta-analyses.
Second, because systematic reviews are based on rules and most often two reviewers independently assess the data, systematic reviews are less prone to author bias. Third, using meta-analyses, systematic reviews can provide a quantitative distillation of apparently conflicting clinical data or identify a trend that might not be evident in a narrative review.
As valuable as systematic reviews can be, their usefulness depends on the focus and quality of the previously published studies. For example, the studies reviewed in this report examined the effects of toothbrushes on plaque and gingivitis. A more important clinical outcome is reduction in caries and periodontal disease. However, the Cochrane researchers did not identify any studies that assessed these clinical outcomes. One might argue that these are difficult studies to conduct. However, it is clear from the Cochrane review of fluoride toothpaste5—in which a 24-percent reduction in caries was found—that studies of caries reduction are possible.
Second, the trial quality influences the results of the review. In the Cochrane toothbrush review, 29 studies (approximately 13 percent of all the studies) met the stipulated standards, while 186 (about 87 percent) did not. If the purpose of a clinical trial is to determine clinical effectiveness and 87 percent of trials were excluded from review because of poor trial design or poor reporting, the review has identified a significant loss of effort and resources in the area of oral health research. More importantly, if 87 percent of the trials do not meet current standards, these substandard trials can generate considerable confusion within the profession and among consumers. This phenomenon was evident in the multiple conflicting press reports emanating from the Cochrane toothbrush review.
The Cochrane researchers’ observation of poor trial quality or reporting in the toothbrush review is not unique. The first 29 completed Cochrane Oral Health Group’s reviews were about diverse topics, including orthodontic treatment, treatment of decay in primary teeth, fluoride varnish, dental implants, dentin hypersensitivity, treatment of temporomandibular joint problems, treatment of precancerous lesions and the oral care of children receiving cancer treatment.
As reported by the Cochrane Oral Health Group, in 27 (93 percent) of these 29 reviews, the evidence provided in the available trials was weak or unreliable. Thus, despite the fact that oral health in the United States is a multibillion-dollar industry, even recent trials do not adhere to Consolidated Standards of Reporting Trials (known as the CONSORT statement), a set of guidelines developed in the mid-1990s by a group of leading international scientists and editors concerned with the quality of medical evidence.6 These standards for trial conduct and reporting are now being implemented by multiple medical journals, and they result in improved clinical trial conduct and reporting.7
Finally, although the Cochrane review evaluated powered toothbrushes, no qualifying studies evaluated the performance of battery-powered toothbrushes—despite the fact that these brushes are widely available in the United States and make up the largest segment of the powered toothbrush market. This occurred because no published studies of the effectiveness of battery-powered toothbrushes lasted 28 days or longer. However, the Cochrane reviews are updated every two to four years; thus, subsequent editions may include reviews of these toothbrushes.
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SUMMARY
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The Cochrane Oral Health Group review of powered toothbrushes was noteworthy for four reasons. First, an international team used international standards to identify, evaluate, compile, analyze and report the data. Second, using these rules-based standards, the review team systematically examined more than 30 years of published studies. Third—and surprisingly—the review indicated that only one type of electric toothbrush demonstrated a statistically significant clinical benefit over manual toothbrushes. Fourth, battery-powered toothbrushes were excluded, because no studies of these brushes met the inclusion criterion of lasting 28 days or longer.
Future studies will need to demonstrate the ability of powered toothbrushes to reduce the incidence and prevalence of caries and periodontal disease, as well as evaluate the relative benefit and cost of the newer battery-powered toothbrushes.
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Dr. Niederman is a consultant to the ADA Council on Scientific Affairs, and is director, DSM-Forsyth Center for Evidence-Based Dentistry, The Forsyth Institute, Boston. He also is an associate professor, Department of Health Policy and Health Services Research, Boston University Goldman School of Dentistry. Address reprint requests to Dr. Niederman at the Forsyth Institute, 140 The Fenway, Boston, Mass. 02115, e-mail "rniederman@forsyth. org".
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FOOTNOTES
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Practical Science is prepared each month by the ADA Council on Scientific Affairs and Division of Science, in cooperation with The Journal of the American Dental Association. The mission of Practical Science is to spotlight what is known, scientifically, about the issues and challenges facing today’s practicing dentists.
Although Practical Science is developed in cooperation with the ADA Council on Scientific Affairs and the Division of Science, the opinions expressed in this article are those of the author and do not necessarily reflect the views and positions of the Council, the Division or the Association.
Dr Niederman acknowledges the authors of the original Cochrane review: M. Heanue, S.A. Deacon, C. Deery, P.G. Robinson, A.D. Walmsley, H. Worthington and W. Shaw.
The author also acknowledges S. Bikley, L. Asbridge, A.M. Glenny and E. Tavender of the Cochrane Oral Health Group, and S. Can, R. Mitezki and G. Lodi for translating original manuscripts that were evaluated by the Oral Health Group.
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REFERENCES
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- Heanue M, Deacon SA, Deery C, et al. Manual versus powered toothbrushing for oral health. Cochrane Database Syst Rev 2003(1):CD002281. Available at: "www.cochrane-oral.man.ac.uk". Accessed July 16, 2003.
- Lemelson-MIT Invention Index Survey (Jan. 21, 2003). Available at: "mit.edu/invent/n-pressreleases/n-press-03index.html". Accessed April 21, 2003.
- Niederman R, Richards D, Matthews D, Shugars D, Worthington H, Shaw W. International standards for clinical trial conduct and reporting. J Dent Res 2003;82:415–6.[Free Full Text]
- Needleman I. A guide to systematic reviews. J Clin Periodontal 2002;29(supplement 3):6–9.
- Marinho VC, Higgins JP, Sheiham A, Logan S. Fluoride tooth-pastes for preventing dental caries in children and adolescents. Cochrane Database Syst Rev 2003;29(1):34–45.
- The CONSORT Group. CONSORT statement. Available at "www.consort-statement.org/". Accessed Aug. 1, 2003.
- Moher D, Jones A, Lepage L. Use of the CONSORT statement and quality of reports of randomized trials: a comparative before-and-after evaluation. JAMA 2001;285:1992–5.[Abstract/Free Full Text]
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