I don't think I was too clear...
Ever since I have started using a Sonicare toothbrush, I haven't gotten any cavities or anything. If everyone started using this toothbrush, the only business that would remain for the dentist would be hygiene, which is rarely even performed by the dentist.
My question is: will there be less demand for general dentistry/endodontistry if electric toothbrushes become the norm? How would that affect dentist incomes?