The American Dental Association recommends replacing the head your electric toothbrush as often as you'd toss your old-fashioned manual toothbrush: every three months. But because the round bristles may not show physical wear as quickly or as obviously as the toothbrushes of your youth, you may forget to upgrade until the head is practically ready to spin off the handle.
It's much easier to piggyback a new habit onto an old one than it is to create a new habit from scratch, explains New York Times
reporter Charles Duhigg in his book The Power of Habit
. So consider replacing your toothbrush head when, say, you’re updating your closet for the new season’s weather, filing expense reports or going through quarterly receipts.