Rotary electric toothbrushes.
This grouping of electric toothbrushes, while encompassing a number of different individual designs, are all similar by way of the fact that their brush heads each contain a set of rotary bristles. The bristles are either set in a circular format that rotates or oscillates, or else the individual tufts of bristles contained in the brush head each possess a spinning motion. Typically these brushes generate somewhere between 3,000 to 7,500 brush strokes per minute but one manufacturer, Braun Oral B, has add a high frequency pulsating motion to enhance the cleaning action of their brush. You will find that rotary brushes comprise a large percentage of electric toothbrushes sold today, both high end and low cost models.

The plaque cleaning action of rotary electric toothbrushes, just like all toothbrushes before them, relies on the scrubbing motion of the bristles of the brush on a tooth's surface (there is no plaque dislodging effect beyond where the bristles actually touch as there is with sonic toothbrushes). However, different than previous generations of electric toothbrushes these brushes often possess the ability to reach into the interproximal (between the teeth) or subgingival (below the gum line) areas to some degree.

Studies evaluating rotary electric toothbrushes, as opposed to the more primitive designs of electric toothbrushes which predate them, has produced a large amount of clinical evidence that shows that these brushes are superior to manual tooth brushing for plaque removal and reduction in gingivitis (gum inflammation). These findings are probably related to both the enhanced cleaning action of the bristle movements of these brushes, and the fact that the effective use of these brushes relies little on the dexterity of the individual using it.

The oscillating / pulsating rotary electric toothbrushes.
Electric toothbrushes that have both an oscillating and pulsating motion, such as the Braun Oral B "3D" model brushes, could certainly be considered to be examples of the pinnacle of conventional (non-sonic) electric toothbrush design.

These brushes have a round brush head that oscillates back and forth at a rate of 7,600 brush strokes per minute. In addition to this motion the Braun Oral B company has incorporated a pulsating action which creates movements somewhere between 20,000 and 40,000 pulses per minute, depending on the specific brush model.

Even with this intense high rate of movement the Braun Oral B "3D" brushes are not considered to be "sonic" type toothbrushes. We are unaware of any claims by the manufacture of a fluid dynamic clean action such as the one generated by sonic toothbrushes. The conventional mode of cleaning produced by these Braun Oral B brushes however, that cleaning created by the toothbrush's bristles scrubbing a tooth's surface, is exceptional (per our van der Weijden et al reference)

Related to the relatively small size of the brush heads of these types of brushes, oscillating/pulsating toothbrushes are intended for use with a tooth-by-tooth technique. Cleaning each side of one tooth before moving on to the next. This is somewhat in contrast to sonic toothbrushes whose more conventional style brush head is intended to be manipulated more like a manual toothbrush.

Other rotary electric toothbrushes.
Previous decades have produced a variety of other rotary electric toothbrush designs. Some of these are:
---- Rota-dent brand toothbrushes.
The tiny brush heads of these brushes possess a single rotating tuft of bristles fashioned in either pointed or cup-shaped form. The cup-shaped brushes are intended for use on larger tooth surfaces while the pointed brushes have been designed for use between teeth.

---- Interplak brand toothbrushes.
These brushes are known as "counterrotational" toothbrushes. The brush head of these brushes looks similar to a standard manual toothbrush but each individual tuft of bristles in the brush head rotates, in opposite direction as its neighbor.

The original generation of electric toothbrushes.
The first electric toothbrushes were primitive mechanized versions of standard manual toothbrushes. The brush stroke action was a simple back and forth movement that attempted to simulate the scrubbing motion accomplished by brushing by hand.

The studies involving this generation of electric toothbrushes were the ones where the researchers found it difficult to show that the use of an electric toothbrush was superior to brushing with a manual one. Even though these types of brushes were first developed and brought to market about 60 years ago, this same design can still be found today in some of the inexpensive lower end electric toothbrushes that are sold.