What would be the benefits of sonic brush?

Timing, dexterity: People who have dexterity problem (stroke victim, arthritis, geriatric population) should used sonic brush since it does all the mechanical movement for you. Secondly, it comes with the timer to make sure you brush the area long enough to achieve good result. Lastly, it produced enough fluid movement to almost produce a flossing effect (adequate for straight teeth area).