Objective: To examine the influence of compressive and deflective force on the filaments of 7 commercially available powered toothbrushes. Method and Materials: The deformation (collapse under force) of the filaments on individual brush heads was measured at a rate of 4 mm/min using an Instron load testing machine under applied loads of 0.5 to 3.0 N. The load was directed perpendicular to the long axis of the filaments. The peak deflection force (deflecting of the filaments from their normal position) was measured with the head of the powered brush oriented horizontally to the applied load. Measurements were taken while the brush head was stationary and during oscillation. Data for peak deflective force were analyzed using a general linear model with post hoc Tukey tests. Results: All powered toothbrushes showed filament deformation when increasing loads were applied. Deformation of the filaments was greatest at 0.5 N and 1.0 N for the Teledyne and was recorded at 1.70 mm and 3.67 mm, respectively. At 2.0 N, greater deformation (5.50 mm) occurred with the Blend-a-Dent, and at 3.0 N, the Sonicare powered toothbrush exhibited a deformation of 3.95 mm. Over the whole range of applied forces, the Braun D15 showed the lowest deformation effects. The different deformations of the filaments recorded between the heads of all powered toothbrushes tested were significant (general linear model, P .001). Also a decrease in peak deflective force was observed between stationary and oscillating toothbrush heads. Conclusions: The compressive and peak deflective forces vary between different brushes, and the ability to resist deformation depends on the arrangement of the filaments on the head of the powered brush. Keywords: compressive deformation, peak deflective force, powered toothbrush