Maybe.

>A Bristle subscription would be more convenient than going to CVS when you need a new toothbrush--you'd order online, set your replacement-head frequency, and forget about it.

Picking up a toothbrush every now and then--assuming you don't just get given them at every cleaning by your dentist--is so far down the list of problems that I and most people have as to be negligible. Furthermore, I doubt if middlemen markups on toothbrushes are a big problem when in fact overheads are probably far lower overall.

There are clearly some things like eyeglasses that the existing market is fairly broken. But most goods simply aren't in that situation.