The Oral-B iO Series 4 electric toothbrush features Oral-B’s best technology, combining a dentist-inspired round brush head with micro-vibrating bristles for a professional purifying clean feel at home. The Smart Pressure Sensor helps prevent you from brushing either too hard or too softly to better protect your gums. Gum Guard alerts you to time spent brushing with too much pressure. Replace your Oral-B iO Brush Head every 3 months for best results.