sonic toothbrush / electric toothbrush: The Sonicare ® toothbrush.

The evolution of the electric toothbrush has come a long way during the last several decades. The first electric toothbrushes were introduced to the consumers' marketplace about 50 years ago. Surprisingly, despite the primitive nature of these toothbrushes and their lack of features, some close relatives of these electric toothbrushes are available yet today.

At the other end of the spectrum, the newest type of electric toothbrush design is the "sonic toothbrush" (as characterized by the Sonicare ® toothbrush). The cleansing action of these brushes is based on a technology that makes it possible for them to have a cleaning effect beyond where the tips of their bristles actually touch. This is a claim no other type of electric toothbrush design has ever been able to make.

Overall it seems that the more recent generations of electric toothbrushes have proven to be the best dental plaque removers. For this reason our discussion will start by describing the sonic toothbrushes, as characterized by the Sonicare ® model, and then work backward in time through earlier electric toothbrush designs.

The sonic toothbrush: Sonicare ® toothbrushes.

The most recent advancement in the design of electric toothbrushes was first incorporated into a product in 1983. This product was the Sonicare ® toothbrush. The class of electric toothbrushes that subsequently grew out of the use of this technology has now become known as the "sonic toothbrushes." Even today the features and capabilities of the Sonicare ® brand of brushes can still be considered to represent the standard for this toothbrush group.

It's easy to identify a sonic toothbrush by way of the high rate of speed at which its brush head vibrates. The brush head of a sonic toothbrush is capable of creating in excess of 30,000 brush strokes per minute. (The latest models of sonic toothbrushes can create more than 40,000 brush strokes per minute. In comparison conventional electric toothbrushes typically operate at frequencies ranging between 2,500 and 7,500 strokes per minute). It is the vibrational motion of these brushes that sets them apart from all previous generations of electric toothbrush design.

How does a Sonicare ® toothbrush work?

The cleaning action generated by a Sonicare ® toothbrush (or any other type of true "sonic toothbrush") is actually based on two separate mechanisms. One of these is conventional and is similar in nature to that mechanism employed by all other types of toothbrushes. The second cleaning action is based on a new technology that was first introduced by Sonicare ® and one that is entirely unique to sonic toothbrushes.

1) The primary mode of cleaning that a sonic toothbrush can provide is that which is produced by the scrubbing action of its brush head's bristles on the surface of the user's teeth. Of course this method of cleaning teeth is not new. All toothbrushes, both electric and manual, rely on this same principle for removing dental plaque. ( More... )

2) Sonicare ® toothbrushes are also capable of producing a secondary cleaning action, one based upon a new technology developed by the brush's creators. This cleaning action is founded on the intense speed at which the bristles of the sonic toothbrush vibrate. This vibratory motion is able to impart energy to the fluids that surround teeth (such as saliva). The motion of these agitated fluids is capable of dislodging dental plaque, even beyond where the bristles of the toothbrush actually touch. Only a sonic toothbrush can make this claim.

About the fluid dynamics created by a Sonicare ® toothbrush.

As we've just mentioned the unique property of a Sonicare ® toothbrush, and that aspect which sets sonic toothbrushes apart from all other types of electric toothbrush designs, is its ability to dislodge and disrupt dental plaque even beyond where the tips of the toothbrush's bristles actually touch. If you were to read a brochure written by the makers of Sonicare ® toothbrushes it quite possibly would read something like this:

The brush head of your sonic toothbrush has been designed to vibrate at more than 30,000 brush strokes per minute. This high speed brushing action in turn creates turbulent fluid dynamics near the tips of its bristles.

The result is the creation of waves of pressure and shear forces in the liquids that surround your teeth, and also the creation of minute bubbles that are propelled forcefully against surfaces where plaque resides. The combination of these various fluid dynamics results in forces that are capable of dislodging dental plaque in those hard to reach areas such as between teeth and below the gum line. The cleaning effect of these fluid forces has been measured to occur at distances of up to 4 millimeters (slightly more than 1/8th of an inch) beyond where the bristles of your sonic toothbrush actually touch.

More about the fluid dynamics cleaning action generated by a sonic toothbrush.

We won't pretend that the cleaning achieved by the fluid dynamics of a sonic toothbrush, the cleaning action that occurs beyond where the tips of the toothbrush's bristles actually touch, results in a tooth surface that is spotless and totally devoid of dental plaque. The fluid dynamics cleaning action produced by a sonic toothbrush is considered to be one of secondary importance. It augments and enhances that cleaning activity created by the conventional scrubbing action of the toothbrush's bristles on the surface of teeth.

We would suggest however that the fluid dynamics created by a sonic toothbrush that can disrupt dental plaque (even if just superficially) and also dilute and wash away the toxins produced by the bacteria that live in dental plaque could overall help to mitigate dental plaque's harmful effects. And while these benefits (which are not provided by other electric toothbrush designs) might only exist for just a short period of time, when one considers the long-term use of a sonic toothbrush over years and decades, these small benefits might prove to be significant. However at this time there is no research that definitively proves this.

Research evaluating the fluid dynamics cleaning action of sonic toothbrushes.

Just to make sure you are well informed about the capabilities of the fluid dynamics cleaning ability of a sonic toothbrush, both its strengths and limitations, here is some information drawn from published dental research. We'd like to point out up front that the setting used for these studies was a "laboratory" environment (in vitro) as opposed to a "clinical" setting (in vivo). To the defense of this criticism, we can see how it would be extremely difficult to quantify the types of measurements described below by direct observation in a person's mouth.

One study was conducted (our Stanford et al reference) where tooth enamel samples were allowed to accumulate a film of dental plaque. These samples were then exposed to the brushing action of either a Sonicare ® toothbrush or else a conventional, non-sonic type, electric toothbrush. After this brushing period the enamel samples were evaluated for cleanliness by way of viewing them under a scanning electron microscope. Here's what the study found:

Variation #1: The Sonicare ® toothbrush was held in direct contact with the enamel sample. [An evaluation of the conventional cleaning (tooth surface scrubbing) action of sonic toothbrushes.]

95% of the dental plaque harbored on the enamel samples was dislodged if the contact between the sonic toothbrush and the enamel surface was for a duration of at least 5 seconds. If the contact time was 10 seconds or longer essentially all of the dental plaque was removed.

Variation #2: The Sonicare ® toothbrush was held 2mm (a little more than 1/16th of an inch) from the surface of the enamel sample surface. [No direct contact between the sonic toothbrush and the enamel sample surface.]

65% of the dental plaque originally inhabiting the enamel sample was removed by the fluid forces generated by the sonic toothbrush when it was held at this distance for at least 5 seconds.

Variation #3: The Sonicare ® toothbrush was held 3mm (just short of 1/8th of an inch) from the surface of the enamel sample surface. [No direct contact between the sonic toothbrush and the enamel sample surface.]

The fluid forces that were generated by the sonic toothbrush were able to produce the following cleaning effects in the listed time frames. 58% plaque reduction at 5 seconds, 63% plaque reduction at 10 seconds, 76% plaque reduction at 15 seconds.

Variation #4: The conventional electric toothbrush [one generating 4,200 brush strokes per minute) was held 3mm from the surface of the enamel sample surface. [No direct contact between the electric toothbrush and the enamel sample surface.]

No significant dental plaque removal was observed.

Variation #5: The conventional electric toothbrush (one generating 4,200 brush strokes per minute) was held in direct contact with the enamel sample.

Actually this study did not evaluate this variation. One would have to assume however that when in direct contact with an enamel surface that a modern conventional electric toothbrush would be a very effective plaque remover.

More about the conventional scrubbing action generated by a sonic toothbrush.

As we mentioned previously, the primary mode of cleaning of a sonic toothbrush is conventional. It's produced by the scrubbing action of the brush's bristles on the surface of teeth.

Sonic toothbrushes do create a very effective brushing action, primarily due to the high number of brush strokes per minute that these toothbrushes can generate. Sonic toothbrushes are capable of producing more than 30,000 brush strokes per minute. Compare that number to the number of brush strokes created by brushing by hand which is generally considered to be in the neighborhood of 300 strokes per minute. The better non-sonic type electric toothbrushes typically generate somewhere between 2,500 and 7,500 brush strokes per minute, which is only about one fourth the number of brush strokes created by sonic toothbrushes.