Electric Toothbrush

An electric toothbrush is a toothbrush that makes rapid automatic bristle motions, either back-and-forth oscillation or rotation-oscillation, in order to clean teeth. Motions at sonic speeds or below are made by a motor. In the case of ultrasonic toothbrushes, ultrasonic motions are produced by a piezoelectric crystal. A modern electric toothbrush is usually powered by a rechargeable battery charged through inductive charging when the brush sits in the charging base between uses.

History
The earliest example of an electric toothbrush was first produced by Tomlinson Moseley. Sold as the Motodent, a patent was filed by his company, Motodent Inc on December 13, 1937. In Switzerland in 1954 Dr. Philippe Guy Woog invented the Broxodent. Woog's electric toothbrushes were originally manufactured in Switzerland for Broxo S.A. The device plugged into a standard wall outlet and ran on line voltage. Electric toothbrushes were initially created for patients with limited motor skills and for orthodontic patients.

Classification
Electric brushes can be classified according to their type of action:


 * Side to side vibration, which has a brush head action that moves laterally from side to side.
 * Counter oscillation, indicates a brush action in which adjacent tufts of bristles rotate in one direction and then the other, independently. Each tuft rotating in the opposite direction to that adjacent to it.
 * Rotation oscillation, indicates a brush action in which the brush head rotates in one direction and then the other.
 * Circular, indicates a brush action in which the brush head rotates in one direction only.
 * Ultrasonic, indicates a brush action where the bristles vibrate at ultrasonic frequencies.
 * Ionic, indicates a brush that aims to impart an electrical charge to the tooth surface with the intent of disrupting the attachment of dental plaque.

Sonic Toothbrush
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 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. One study found that using sonic toothbrush causes less abrasion to the gum when compared to the manual toothbrush.

Ultrasonic toothbrush
The newest developments in this field are ultrasonic toothbrushes, which use ultrasonic waves to clean the teeth. In order for a toothbrush to be considered "ultrasonic" it has to emit a wave at a minimum frequency of 20,000 Hz or 2,400,000 movements per minute. Typically, ultrasonic toothbrushes approved by the U.S. Food and Drug Administration (FDA) operate at a frequency of 1.6 MHz, which translates to 192,000,000 movements per minute.

Ultrasonic toothbrushes emit vibrations that are very high in frequency but low in amplitude. These vibrations break up bacterial chains that make up dental plaque and remove their methods of attachment to the tooth surface up to 5 mm below the gum line.