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The crossover design to evaluate the efficacy of plaque removal in tooth-brushing studies
Article first published online: 6 OCT 2005
DOI: 10.1111/j.1600-051X.2005.00843.x
Additional Information
How to Cite
McCracken, G. I., Steen, N. , Preshaw, P. M., Heasman, L., Stacey, F. and Heasman, P. A. (2005), The crossover design to evaluate the efficacy of plaque removal in tooth-brushing studies. Journal of Clinical Periodontology, 32: 1157–1162. doi: 10.1111/j.1600-051X.2005.00843.x
Publication History
- Issue published online: 6 OCT 2005
- Article first published online: 6 OCT 2005
- Accepted for publication 29 July 2005
- Abstract
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Keywords:
- plaque removal;
- powered toothbrushes;
- trial design
Abstract
Objectives: To evaluate the crossover clinical trial design to assess plaque removal efficacy of the Sonicare Elite.
Material and Methods: A single-cohort, 12-week, two-treatment, single-blind, crossover clinical trial recruited 45 subjects. Plaque was recorded using the modified Quigley and Hein index plaque index (PI). After screening, subjects used the toothbrush for 2 weeks and were reminded to abstain from tooth cleaning 12–18 h prior to appointments. At visit two, subjects were randomized to 2 or 2½ min. brushing time. PIs was recorded pre- and post-brushing. Subjects brushed for the allocated time for a further 2 weeks. At visit 3, PIs were recorded pre- and post-brushing. Two weeks later, at visit 4, the subjects crossed over and the protocol was repeated.
Results: There was no evidence of a learning effect within each arm of the crossover. A significant period effect was detected; however, no significant treatment by period effect was found. 2½ min. brushing removed more plaque at full mouth (p=0.037), smooth (p=0.012) and lingual (p=0.002) sites compared with 2 min.
Conclusion: The crossover design is a valid model for assessing plaque removal efficacy in tooth-brushing studies where no carry-over effect is clinically plausible.