Electric brushes can be classified into two categories according to the type of action that they employ: vibration or rotation-oscillation. When using vibrating toothbrush, a brushing technique similar to that used with a manual toothbrush is recommended, whereas with rotating-oscillating brushes the recommend cleaning technique is to simply move the brush slowly from tooth to tooth.[5]
Electric toothbrushes can also be classified according to the speed of their movements as standard power toothbrushes, sonic toothbrushes or ultrasonic toothbrushes. If the motion of the toothbrush is sufficiently rapid to produce a hum in the audible frequency of human range (20 Hz to 20,000 Hz), it can be classified as a sonic toothbrush. Any electric toothbrush with movement faster than this limit can be classified as an ultrasonic toothbrush. Certain ultrasonic toothbrushes, such as the Megasonex and the Ultreo, have both sonic and ultrasonic movements.[6]
Sonic toothbrushes are a subset of electric toothbrushes with movement that is fast enough to produce vibration in the audible range. Most modern rechargeable electric toothbrushes from brands such as Sonicare, FOREO, and Oral-B fall into this category and typically have a frequencies that range from 200 to 400 Hz, that is 12,000-24,000 oscillations or 24,000-48,000 movements per minute. Because sonic toothbrushes rely on sweeping motion alone to clean the teeth, the movement that they provide is often high in amplitude, meaning that the length of the sweeping movements that they make is large.
