Are electric toothbrushes more efficient than manual toothbrushes? Yes, of course they are!
But... do they remove 100% more plaque than a manual toothbrush? No.
With proper brushing technique you can achieve thorough plaque removal using a regular manual toothbrush.
As with electric toothbrushes, manual toothbrushes also differ in quality and efficiency. And studies have been made putting a range of different quality electric toothbrushes face-to-face against a range of different quality manual toothbrushes.
The electric toothbrushes are just as safe as manual toothbrushes, removed 10 - 49% more Plaque and reduced Gingivitus by 8 - 40% over the same time of usage.
2 out of 10 people did not get any benefit whatsoever from an electric toothbrush over a manual toothbrush.
For sure an electric toothbrush is more efficient than a manual toothbrush in general. There is no argumenting that. But it's not an increase of 100%.. That is like saying you are 2 meters tall when you are in fact only 1 and a half meter.
Keep in mind that an electric toothbrush requires precious energy to work and uses toxic batteries that should be disposed of properly.