The influence on plaque-removing efficiency of the alternating frequency of a powered brush has never been established. In the present study, a mechanical brush was tested at various alternations per minute (F1 = 2100, F2 = 2500, F3 = 3500). A double-blind, randomized, triple crossover design was applied. After a plaque growth phase, the test brushes were used under supervision for 90 s and the remaining plaque scored. A ridit analysis yielded significant differences between F2 and F1/F3. Odds ratios and frequency distributions demonstrated a clinically meaningful advantage for F2. Subjective evaluation by the participants confirmed the positive performance of F2. The results can be generalized in 3 ways: (1) the alternating frequency of a power brush influences its effectiveness, (2) high frequencies are not generally superior, (3) the test brush has its optimal cleaning efficiency at F2, which does not necessarily need to be true for other brands. It seems imperative to determine the optimal frequency for any new brush in a controlled study.