The Sonicare FlexCare and the Oral-B Triumph Professional Care 9000 power toothbrushes were compared in a single-use, examiner-masked, crossover clinical trial. Outcomes were evaluated using the Turesky Modified Quigley-Hein (TMQH) plaque index. Percent reduction in overall plaque score because of toothbrushing was the primary efficacy measure. Subjects were required to have a TMQH score > or = 1.8 at screening after refraining from oral hygiene for 24 hours. The study included three visits. At visit 1, subjects were randomized to one of two treatment sequences, given their first toothbrush and toothpaste, and instructed to use them twice daily for 2 minutes during a 1-week familiarization phase. Before visit 2, subjects again refrained from oral hygiene for 24 hours. At this visit, plaque scores were assessed before and after a 2-minute supervised brushing episode, then the second test product was issued. Familiarization, plaque accumulation, and clinical examinations were the same for both product use periods. Data were analyzed using a linear mixed effects model with subject as a grouping factor. Treatment effects were expressed as mean values and the appropriate 95% confidence intervals (CI). Ninety-six subjects were screened with 93 subjects completing the study. The sample's TMQH score at Visit 1 was 3.18 +/- 0.42 (mean +/- standard deviation [SD]). Full-mouth prebrushing plaque scores were 2.85 +/- 0.49 for FlexCare and 2.94 +/- 0.45 for Triumph. Respective full-mouth reductions in overall plaque score were 38.02% +/- 15.14% and 30.43% +/- 14.05%. The estimated treatment effect, expressed as difference between FlexCare and Triumph in percent plaque index reduction, was 7.59% with a 95% CI from 4.79% to 10.40%. Similar differences were observed for all subregions, including anterior, posterior, interproximal, and interproximal posterior sites. The same protocol design was used at an earlier study in another center. The combined overall treatment effect from the two studies was estimated at 6.97% (95% CI: 5.17%, 8.78%), favoring FlexCare.