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RESEARCH REPORT |
1 WHO Collaborating Centre 309 for Oral Health Care Planning and Future Scenarios, and Department of Preventive and Restorative Dentistry, Radboud University Nijmegen Medical Centre, Nijmegen, PO Box 9101, 6500 HB Nijmegen, The Netherlands;
2 Oral Health Unit, Department of Health, Yangon, Burma; and
3 Department of Periodontology, Academic Center for Dentistry Amsterdam (ACTA), The Netherlands
* corresponding author, w.vanpalenstein{at}dent.umcn.nl
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS & METHODSRESULTSDISCUSSIONREFERENCES |
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KEY WORDS: worn toothbrushes • dental plaque • non-inferiority study • period effects • oral hygiene
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS & METHODSRESULTSDISCUSSIONREFERENCES |
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Studies with naturally worn toothbrushes reported no statistically significant difference in whole-mouth plaque scores after brushing when worn and new toothbrushes were compared (Daly et al., 1996; Sforza et al., 2000; Tan and Daly, 2002; Conforti et al., 2003), except for one that reported statistically significantly more plaque removal (23%) after brushing with a two-week-old brush as compared with a 10-week-old brush (Glaze and Wade, 1986). Two studies (Daly et al., 1996; Tan and Daly, 2002) indicated no difference at all in the plaque-removing efficacy of heavily worn toothbrushes as compared with that of toothbrushes with minor wear or no wear. The two other cited studies (Sforza et al., 2000; Conforti et al., 2003) showed statistically non-significantly higher plaque scores after brushing with three-month-old toothbrushes as compared with one-month-old toothbrushes. The lack of statistical significance in these latter two studies may be due to lack of sufficient power.
From this brief review of the literature, it may be concluded that, in contrast to what is generally thought, the wear status of a toothbrush might be less critical for the maintenance of good plaque control. Cited studies were all performed with adults. This raises the question whether the reported findings are applicable to young children. This is particularly relevant in the context of affordability of school-based toothbrushing programs in low-income countries.
We therefore decided to conduct a randomized cross-over clinical trial to validate or invalidate the hypothesis that old toothbrushes in the hands of schoolchildren were not less effective than new toothbrushes with regard to plaque removal.
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MATERIALS & METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS & METHODSRESULTSDISCUSSIONREFERENCES |
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).
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Plaque Scoring
Plaque was disclosed by the application of Mira-2-Ton® solution (Hager & Werken, GmbH & Co., Duisburg, Germany). Plaque was assessed on upper and lower permanent incisors and permanent first molars by means of a modified Quigley-Hein Index (Quigley and Hein, 1962; Turesky et al., 1970; Lobene et al., 1982). Each tooth was divided into 6 surfaces: distal-vestibular, mid-vestibular, mesial-vestibular, distal-lingual, mid-lingual, and mesial-lingual. Each surface of a tooth was scored on a six-point scale:
Score 0 No plaque
Score 1 The presence of a discontinuous line of plaque at the gingival margin, e.g., small islands
Score 2 A continuous line of plaque, at the gingival margin, which does not extend greater than 1 mm from the margin
Score 3 Plaque coverage which is greater than 1 mm but does not extend over more than one-third of the tooth
Score 4 Plaque which covers more than one-third but not more than two-thirds of the tooth surface
Score 5 Plaque coverage over more than two-thirds of the tooth surface
Each child was examined by two examiners (MTA and WS). These examiners were instructed and calibrated by an experienced examiner (NAMR). This examiner had been trained and calibrated in the plaque-scoring system and had applied it in other studies (Rosema et al., 2005; van der Weijden et al., 2005). The plaque-scoring system was explained with the use of clinical, colored photographic images prepared by the investigators showing the different locations of plaque and the concomitant score. This visual training session was followed by two days’ calibration of plaque scoring in children. The tooth surfaces were dried with compressed air and examined with an intra-oral fiber-optic light and a mouth mirror (Fiberoptic Aspirators & Instruments, Duncanville, TX, USA). The children were placed in a supine position on a long classroom bench, with their heads on a pillow on the lap of the examiner, who sat behind them.
Experimental Design
The two examiners scored the plaque of all children. At the first session, plaque was disclosed and scored successively by the two examiners, to obtain the mean of a duplicate plaque score before the children brushed their teeth. Next, the children were randomly allocated either to a new toothbrush or to their own used toothbrush. Randomization was performed with true random numbers, which we generated by sampling and processing a source of entropy outside the computer (see www.random.org). With the use of a mono-jet syringe (Tyco Health Care, Mansfield, MA, USA), the amount of toothpaste (0.4 mL, FreshUp, Myanmar) was standardized and placed on the toothbrush. The children were instructed to brush their teeth to the best of their ability, without any time restriction and without the help of a mirror. The time each child spent brushing was recorded with a stopwatch. At the completion of brushing, the children rinsed with a fixed amount (30 mL) of water for 10 sec. Subsequently, the child’s plaque was disclosed and scored again successively by the two examiners, who had no insight into the baseline score and who were unaware of the brush assignment (new or old). At a second session, 2 wks later, the described procedure was repeated. The only difference was that the toothbrush allocation was opposite that used at the first session. Children continued to use their old toothbrush in the interval between the two visits.
Sample Size
The lower limit for non-inferiority was set at 15%. The ADA states, in its Acceptance Program Guidelines—Toothbrushes (1998), that, under unsupervised conditions, a 15% statistically significant reduction in plaque is needed to provide evidence of greater effectiveness in the cleaning of teeth. Based upon the first set of 20 children, the mean plaque score and standard deviation after brushing with an old brush were calculated. On the basis of the assessed mean plaque score of 2.0, with a standard deviation of 0.7, with the inferiority lower limit of 15% and an upper limit of 100%, alpha = 0.05 and beta = 0.10, the final sample size was calculated to be n = 93. When we accounted for a 10% drop-out for the second session, we had a baseline sample size of n = 103.
Toothbrush Wear
Toothbrush wear was not assessed, since no clear variation was apparent in severe bristle-matting of the 14-month-old toothbrushes.
Statistical Analysis
Data were entered into a database, checked for errors, and analyzed with the use of SPSS-12 software (release 6.i version). Pearson’s correlation coefficients were computed as a measure of association between parameters. Plaque scores of both examiners were averaged for each child in further analyses. Cronbach’s alpha was calculated as a measure of reliability for the mean score of both examiners.
The chosen measure of brush effect (B) was: mean plaque score after brushing with old brushes minus mean plaque score after brushing with new brushes. The relative brush effect (%B) was: B divided by mean plaque score after brushing with old brushes. Confidence intervals for non-inferiority comparisons were one-sided (1.645 x SE).
The brush effect (B) and the period effect (P) were separated (Pocock, 1982) (Table 1). The analysis of B with the correction for possible P was applied not to counteract bias, but to diminish the noise caused by the P, and thus to reduce the width of the confidence interval. This method is equivalent to a mixed-model approach. The presented p-values were based on the paired t test.
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS & METHODSRESULTSDISCUSSIONREFERENCES |
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Examples of the condition of the 14-month-old toothbrushes are shown in the Fig. 
With the aid of a randomization list, 9 14-month-old toothbrushes were selected from the 101 toothbrushes of the participating children.
Mean plaque scores before children brushed with old or new toothbrushes differed slightly, but not statistically significantly (Table 2). The mean overall reduction in plaque scores, as a result of brushing with old and new brushes, was 0.5 and 0.7, respectively (Table 2). Expressed as a percentage of the pre-brushing plaque score, the reductions in plaque score were 16% for old brushes and 24% for new brushes. Plaque reductions for incisors were greater (p < 0.01) than for molars, and greater (p < 0.01) for vestibular surfaces than for lingual surfaces.
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). This difference, defined as brush effect (B), was 0.26 (90%CI, 0.16, 0.34, p < 0.001). The %B was 10.9% (90%CI, 6.7%, 14.3%).
When we took the period effect (P) into account in the estimation of the brush effect (Table 1), the confidence limits of the B and the %B became smaller: 0.18–0.33 and 7.6%–13.9%, respectively.
No difference in brushing time for old and new toothbrushes was observed, but a period effect was present, since a statistically significant (p < 0.01) shorter (12%) brushing time was used at the 2nd session as compared with the 1st session (Table 3).
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS & METHODSRESULTSDISCUSSIONREFERENCES |
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The analyses detected the existence of a period effect in this study. Period effects are caused by a combination of factors, induced, in this study, by children and examiners. Examiners recorded higher plaque scores at the 2nd session as compared with the 1st session (Table 1). This effect could be the result of more critical assessment of the plaque at the second session. However, it seems more likely that the period effect was caused by the children, since they used statistically significantly less time (14.5 sec) for brushing at the 2nd session (Table 3). A novelty effect is not a likely bias in this study, since no association was found between toothbrushing time and the use of old or new toothbrushes.
Since this study aimed to assess the plaque-removal capacity of toothbrushes in the hands of children, we did not want to interfere in the way the children brushed their teeth, and hence a standardized brushing time was not used. The time that these children needed to brush their teeth as well as possible was not exceptionally long: about 2 min at the first visit and about 15 sec less at the second visit. A brushing time of 2 min is regarded as optimal (van der Weijden et al., 1993). Habitual brushing times of these children are probably shorter at home, but brushing time was longer in the school brushing program under teacher supervision.
The %B was 10.9% (90%CI, 7.6%, 13.9%) in favor of new toothbrushes. Despite the fact of statistical significance, the CI of this difference was within the range of 15%, and therefore the hypothesis that old toothbrushes are not less effective than new toothbrushes was validated in this study. A difference in %B of less than 15% was considered a priori as clinically irrelevant for this age group: first, because the anti-caries efficacy of toothbrushing is more the result of the application of fluoride from the toothpaste than the mechanical cleaning per se (Koch and Lindhe, 1970); second, because such a small difference in cleaning efficacy does not exert different anti-caries effects (Bellini et al., 1981); and third, because small differences in cleaning efficiency have a negligible effect on the condition of the periodontal tissues in young children. Even in young adults, a reported difference in plaque score of 23% did not result in substantial differences in the gingival index (Glaze and Wade, 1986).
The observed plaque reductions—16% after the children brushed with old toothbrushes, and 24% after they brushed with new toothbrushes—were relatively small, in light of the review by Jepsen (1998), who stated that a plaque reduction of approximately 50% can usually be expected from manual toothbrushing. However, in a recent study where the plaque-removal efficacy of a powered toothbrush (Sonicare Elite) was compared with that of a soft-filament manual toothbrush (Oral-B 35, Oral-B Laboratories, Belmont, CA, USA), plaque reductions were 36% and 26%, respectively (Moritis et al., 2002). Despite their apparent efforts, adults, let alone children, do not appear to be as efficient at plaque control as one might hope (Morris et al., 2001).
The finding that heavily worn 14-month-old toothbrushes with severe bristle matting in the hands of 7- and 8-year-olds are not less effective than new toothbrushes with regard to plaque-removal capacity has important consequences for school brushing programs. If the old toothbrush can be maintained far beyond the generally recommended three-month period, school-based toothbrushing programs in underserved communities have a better chance to be sustained.
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ACKNOWLEDGMENTS |
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Received November 1, 2005; Last revision May 31, 2006; Accepted September 5, 2006
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REFERENCES |
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Koch G, Lindhe J (1970). The state of the gingivae and caries increment in school children during and after withdrawal of various prophylactic measures. In: Dental plaque. McHugh WD, editor. Edinburgh: Livingstone, pp. 271–281.
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