When your toothbrush is no longer up to performing its primary task (the American Dental Association recommends replacing yours every three to four months), take a beat before tossing it in the trash.

The old family toothbrush That hangs by the sink. First it was father’s . . . Almost as bad as the toothbrush of this parody, say Dentists Allen O. Gruebbel and J. M. Wisan, is the actual toothbrush ...