It is the electric toothbrush which makes users clean teeth easily and effectively in the way recommended by dentists. The 3D acceleration sensor detects the angle of the brush and recognizes the part to switch to optimal brush swing automatically. It makes an optimal angle for cleaning periodontal pocket by placing the thumb on the thumb point and indicates the light. Users can check the proper brushing angle. The original S shaped design enables to clean the back teeth and the inner side of the front teeth. The battery charger has a 2 min. navigation timer to inform elapsed time with a light (only HT-B551).