Objectives: Primary objective - To determine the effect of varying brushing forces and brushing times upon the plaque-removing efficacy of a powered toothbrush. Secondary objective - to determine the optimum combination of brushing force and time for plaque removal.
Material and methods: This randomised, single-blind, 16-cell, cross-over trial compared the efficacy of plaque removal of a powered toothbrush (PTB) used with four brushing forces (75, 150, 225 and 300 g) and over four brushing times (30, 60, 120 and 180 s). Twelve volunteers (18-30 years) were recruited and trained to use the Philips/Jordan Sensiflex 2000 PTB, which was modified so that specified forces and times could be recorded. Each subject was asked to abstain from all oral hygiene procedures for 24 hs prior to each brushing event, to allow plaque accumulation. Plaque was recorded using a modified Quigley & Hein index (PI) at six points per tooth before and after each episode of brushing, and the differences in the means (pre- to postbrushing) were compared. Three-way anova was undertaken to compare differences between plaque-removing efficacy for the 16 combinations of force and time. Subjects, brushing time and brushing force were used as fixed effects within the analysis.
Results: All 12 subjects participating completed the 16 combinations of force and time over which plaque removal was assessed. Statistically significant differences in PI reductions were found between different brushing times and forces over all tooth surfaces (p<0.001). The interaction of varying brushing force and brushing time was significant for full mouth (FM) and interproximal (IP) sites (p<0.03). No statistical significance was demonstrated for smooth surface (SS) sites, nor was it detected for the interaction of subjects with brushing force or subjects with brushing time (p>0.05).
Conclusion: We conclude that brushing time and brushing force have significant effects upon the level of plaque removal by a PTB, and at 120 s brushing time the improvement in plaque removal with forces in excess of 150 g was negligible.