Toothbrush bristle density: relationship to plaque removal

A double-blind, parallel, controlled study was conducted to determine the effect of toothbrush bristle density (total number of bristles divided by the brush head area) in removing plaque from tooth surfaces. Ninety subjects (29 males, 61 females), aged 18-65, were randomly assigned to one of three groups using the Sensodyne Search 4-Rowa toothbrush modified to have the following bristle densities: A (4.5 bristles per mm2); B (8.3 bristles per mm2); or C (11.8 bristles per mm2). The average trim height of the bristles was 10.77 mm. Subjects brushed without any dentifrice once a day for 7 days in order for adherent deposits (salivary pellicle and plaque remnants) to accumulate on their teeth. On the eight day, examinations for stained deposits were performed according to the Global Scoring Index before and after one minute of brushing with a commercially available toothpaste. Percent reductions in deposits were highly significant for the eighty-seven subjects who completed the study. A paired t-test between the pre- and post-treatment scores (p = 0.005) demonstrated the following: Toothbrushes A, B and C had reductions in plaque of 45.5%, 51.9% and 56.8%, respectively. On an overall basis, the intergroup percent reductions were significantly different using ANOVA (p = 0.001), and demonstrated a relationship in terms of data clustering for percent plaque removal of toothbrushes with varied bristle densities.