Rotary Electric Toothbrushes - These brushes have either a circular arrangement of bristles or they are arranged as in a manual toothbrush. When battery of toothbrush is switched on bristles of toothbrush start vibrating. Bristles move in an oscillating or pulsating motion at a frequency of 3000-7500 brush strokes per minute. The cleaning action of these brushes is primarily by scrubbing the teeth when oscillating bristles come in contact with the teeth. They can have 2 types of motions:

  1. Oscillating/pulsating
  2. Spinning motion

Sonic Toothbrushes

They are based on more advanced technology then rotary toothbrushes. They work on the principle of oscillating motion as well as “acoustic streaming action” for disruption of plaque. The first toothbrush of this type was introduced in 1983 under the trade name “Sonicare”. It is capable of generating 30000-40000 strokes per minute. 2 principle mechanisms on which it works:
  1. Scrubbing action of oscillating bristles cleanses the surface of teeth in contact with bristles. This action is similar to the one performed by rotary toothbrush.
  2. Acoustic streaming: When the bristles of sonic toothbrush vibrate at a very high speed they impart energy to the fluid surrounding the teeth i.e. saliva. On gaining energy waves of pressure are created in these fluid molecules and bubbles are formed which get propelled against the surfaces of teeth where the plaque is present. So, plaque is disrupted even from the areas which are beyond the reach of bristlessuch as in between teeth and below the gum line. It has been found that this action of acoustic streaming for disruption of plaque is seen 4mm beyond the reach of bristles.

Power Source & Charging of Electric Toothbrush

The electronic compartments of the powered toothbrushes are completely sealed so as to prevent any water damage. Electric toothbrushes are cordless and consist of rechargeable batteries. The indicator gauges are incorporated in the design of the toothbrush so that person using it may know the degree to which battery is charged and when does it require recharging. The base of the toothbrush is sometimes compact so that it can be easily carried while travelling and at other times it is quite large so that many brush heads can be stored in its base.

As there are no metal contacts in the tooth brush it gets charged when base of toothbrush is kept in contact with the charger by a phenomenon called inductive charging. The toothbrush and its base form a two-part transformer, such that base is having one part of the transformer and the toothbrush having the other. When electric toothbrush is slide onto the base, the complete transformer is created through which charge can flow. So, when base is applied to the charger, the battery gets recharged by the flow of charge through this transformer.

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