How do Sonicare toothbrushes work? / How effective are they?

Sonicare Toothbrushes

The newest type of electric toothbrush design is the "sonic" brush (as exemplified by the Sonicare product line).

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 the only type of electric toothbrush that can make this claim.

Sonicare is a registered trademark of Koninklijke Philips Electronics N.V.

Sonic technology = A high rate of vibrational speed.

It's easy to identify a sonic toothbrush by the high rate of speed with which its brush head vibrates. These brushes are capable of creating in excess of 30,000 brush-strokes-per-minute. In comparison, conventional electric toothbrushes typically operate at frequencies ranging between 2,500 and 7,500 strokes-per-minute. It's this high rate of vibrational motion that sets sonic brushes apart from all previous generations of electric-toothbrush design.

How does a Sonicare toothbrush work?

A Sonicare toothbrush.

The tooth-cleansing ability of a sonic brush is due to two separate mechanisms. One is conventional (and similar to the way that all other electric toothbrushes work). The second is based on sonic technology (and is entirely unique to this type of brush).

a) Mechanical scrubbing.

The biggest part of the cleaning action generated by a sonic toothbrush is produced by the scrubbing action of its 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 ... )

b) Fluid dynamics.

Sonic toothbrushes also create a secondary cleaning action. This one's created by the intense speed with which their bristles vibrate.

This bristle motion is able to impart energy to the fluids that surround teeth (such as saliva). In turn, these agitated fluids are able to disrupt dental plaque, even beyond where the bristles actually touch. Only a sonic toothbrush can make this type of claim.

How do these "fluid dynamics" work?

If you were to see a brochure describing how a Sonicare works, it might read something like this:

Sonic toothbrushes can dislodge plaque using fluid dynamics.

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 creates pressure waves and shear forces in the liquids that surround your teeth. It also generates minute bubbles that are forcefully propelled against surfaces where plaque has accumulated.

All combined, these fluid dynamics are able to disrupt dental plaque in those hard to reach areas such as between teeth and below the gum line.

This cleaning effect takes place at a distance of up to 4 millimeters (slightly more than 1/8th of an inch) beyond where the bristles of your Sonicare toothbrush actually touch.

How effective are these fluid dynamics at removing dental plaque?

A sonic toothbrush produces fluid dynamics that help to remove dental plaque.

We won't pretend that the fluid dynamics created by a sonic toothbrush (the cleaning action that occurs beyond where the tips of its bristles actually touch) remove dental plaque 100%.

In fact, this type of cleaning is only considered to be of secondary importance. It augments and enhances that basic cleaning activity created by the conventional scrubbing action of the toothbrush's bristles on the surface of the user's teeth.

It can be stated, however, that this fluid action does help to disrupt plaque colonies, which, in turn, helps to inhibit their further growth and development. It also dilutes and washes away the toxins produced by the bacteria that live in them. Both of these actions can help to minimize dental plaque's harmful effects.

We don't want to mislead you ...

When one considers the long-term use of a sonic toothbrush over years and decades, the additional benefits that it can provide (as compared to a conventional electric brush) may prove to be significant. However, at this time there is no research that has definitively proven that it will.

Dental research - How effective is the fluid-dynamics cleansing?

Just to make sure you are well informed about how well the fluid-dynamics cleaning ability of a sonic toothbrush works, both its strengths and limitations, here's 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 an oral (in vivo) one. 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.

A conventional electric toothbrush creates fewer brush-strokes-per-minute than a sonic one.

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

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

This scrubbing motion is very effective, primarily due to the high number of brush strokes per minute these types of brushes generate. Sonic toothbrushes are capable of producing more than 30,000.

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 per-minute.

The better, non-sonic type, electric toothbrushes typically work at a rate of 2,500 to 7,500 brush-strokes-per-minute, which is only about one fourth the number created by a sonic one.

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