The crossover design to evaluate the efficacy of plaque removal in tooth-brushing studies

Authors: McCracken, G. I.¹; Steen, N.²; Preshaw, P. M.¹; Heasman, L.¹; Stacey, F.¹; Heasman, P. A.¹

Source: Journal of Clinical Periodontology, Volume 32, Number 11, November 2005 , pp. 1157-1162(6)

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Abstract:

McCracken GI, Steen N, Preshaw PM, Heasman L, Stacey F, Heasman PA. The crossover design to evaluate the efficacy of plaque removal in tooth-brushing studies.

J Clin Periodontol 2005; 32: 1157-1162. doi: 10.1111/j.1600-051X.2005.00843.x. © Blackwell Munksgaard, 2005. 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.

Keywords: plaque removal; powered toothbrushes; trial design

Document Type: Research article

DOI: http://dx.doi.org/10.1111/j.1600-051X.2005.00843.x

Affiliations: 1: School of Dental Sciences, University of Newcastle upon Tyne, Newcastle upon Tyne, UK; 2: Centre for Health Services Research, University of Newcastle upon Tyne, Newcastle upon Tyne, UK

Publication date: 2005-11-01

The crossover design to evaluate the efficacy of plaque removal in tooth-brushing studies

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