Philips Sonicare 2100 Series Electric Toothbrush HX3651/32 (Light Blue)Sonic Water Flow: High speed vibrations of approximately 31,000 strokes per minute loosen plaque, and the wide range of the brush head's oscillations gently removes it. At the same time, these movements generate a "sonic water flow" in the mouth, encouraging saliva to flow and gently remove plaque. Gentle to Use: The sonic water flow is gentle and suitable for orthodontic appliances and dental prostheses (fillings, crowns, laminate veneers). Smart