Primary objective: To evaluate a multicentre clinical trial design for testing powered toothbrushes.
Secondary objective: To compare the efficacy of a prototype brush head (N2.3) for the Philips Jordan Sensiflex 2000 powered toothbrush (PTB) to that of Braun Oral-B D15 PTB in removing dental plaque
Material and methods: 137 volunteers (ages 18-25 years) were recruited to this 3-centre, 2-week, 2-group, 2-treatment, single-blind trial. Plaque was recorded at screening and again 14 days later at baseline. Stratification of subjects, for gender and screening PI, occurred at baseline. Subjects were then asked to abstain from all oral hygiene measures for 48 h followed by a supervised episode of brushing for 3 min with the allocated PTB. The allocated PTB was used at home for the next 12 days before a second abstinence from all oral hygiene measures for the 48 h prior to a second supervised brushing episode. Plaque levels were scored using a modification of the Quigley & Hein plaque index (PI) at full mouth (FM), interproximal (IP) and smooth surfaces (SS). To enable the means of the within subject differences (pre to postbrushing) to be compared between groups PIs were recorded before and after the supervised brushing episodes, differences between centres, groups and visits were examined.
Results: No significant differences in PI between groups at screening, baseline or prior to the supervised brushings were detected (P > 0.05 anova). The results of the analysis of variance showed there to be a highly significant difference (P < 0.001) between brushing groups, but, significant differences between centres (P < 0.001) and a significant interaction effect between centre and brushing group (P < 0.001) was also detected. Therefore the difference between groups was not present at all three centres. Further examination of the single centre data showed there to be greater levels of plaque removed by the N2.3 compared to the D15 (FM reduction in PI 1.95 vs. 1.13, respectively) at centre 3 in contrast to the other two centres where no difference was detected. The precise reason for these differences could not be established.
Conclusions: A multicentre study design is applicable for evaluating PTBs but a minimum of 3 centres should be included so that differences between centres can be identified. The prototype brush head N2.3 for the Philips Jordan Sensiflex 2000 PTB has comparable plaque removal efficacy to the Braun Oral-B D15 PTB at FM, IP and SS sites.