Mechanical oral hygiene instruments are intended to aid in the removal of stain and dental plaque from tooth surfaces. Certain home hygiene procedures, however, can lead to soft and hard tissue trauma. Power assisted brushing instruments are gaining in popularity, yet there is limited information on the interaction of these home care instruments with commercial dentifrices, and the resultant impact on oral tissues. In this study, the average forces applied during in vivo toothbrushing were determined for three powered brushing instruments (Rota-dent, Interplak and Braun Oral-B Plaque Remover) and a manual toothbrush (Oral-B P40). The Rota-dent instrument was found to be used with the lowest brushing pressure followed, in order, by the Braun Oral-B Plaque Remover. Interplak and the manual toothbrush. The average amount of dentifrice applied to the three powered brush heads was directly related to the size of the head, with Rota-dent typically receiving the least and Interplak the most applied dentifrice.