Brush Head Retention of Powered Toothbrushes as Consumer Safety Measure

The typical power toothbrush design includes a moving brush head (bristled disc) mounted on a shaft which in most cases is defined as a small part.  If dislodged, this part presents a potential choking hazard. Therefore, robust testing methods to assess retention forces are critical to ensure consumer safety during use. Objective: Demonstrate that static brush head pull force in and of itself is the most appropriate test parameter to evaluate brush head retention. Methods: Simulate in-use conditions in vitro using high speed video analysis to observe brush head movement when sufficient force is applied to result in brush head detachment. Results: High speed video analysis shows that when sufficient force is applied to the brush head it stops moving prior to detachment, which occurs at random oscillation angles.  Static pull testing carried out at random oscillation angles on various commercially available brands with a significant market share, e.g. Oral B, ranged from 92-174 N. Modeling and simulation was developed as a design tool to ensure the mechanical integrity before building molded samples and correlates to the laboratory data. Conclusions: These data demonstrate that movement of the brush head stops prior to its detachment. Furthermore, under no condition was the pull force < 90 N. Therefore, pull force testing of the brush head while static is representative of brush head movement at the time of dislodgement during consumer use. Additionally the > 90 N pull force requirement set forth in the European toy standard¹ is appropriate for a minimum brush head retention threshold. Static pull force testing of power brush heads is proposed as a method to aid brush head design to ensure safety of consumers during use.