Aim: To compare the effectiveness of new and 3‐month‐old worn brush heads in plaque removal using a rotation–oscillation‐powered toothbrush. Material and Methods: A single examiner blinded, randomized, cross‐over study was conducted in which 34 adults attended the clinic on two occasions following 48‐h periods of no oral hygiene. Following plaque scoring, subjects brushed for 2 min. with either a new brush or a brush they had used for 3 months and plaque was then re‐scored. Bristle wear was assessed by measuring brushing surface areas on digital images. Results: The mean plaque score percentage reductions with new brush heads were not significantly different from those achieved with 3‐month‐old heads for total surfaces (new=38.1%; worn=37.1%; p=0.83) and approximal surfaces (new=31.3%; worn=30.8%; p=0.9). Brushing surface area increases of the 3‐month‐old heads ranged from 0% to 135% (mean 26.9%). Compared with new brush heads, no significant differences were found for plaque score reductions for heads with minor, moderate or marked wear. Conclusion: Rotation–oscillation‐powered toothbrushes with 3‐month‐old brush heads exhibiting various degrees of wear were as effective as new brush heads in plaque removal. Bristle age and wear on a powered toothbrush may not impede the effectiveness of plaque removal.