Too many people wait too long to get a new toothbrush, and this can contribute to poor dental health. At Harris Dental in Phoenix AZ we recommend a new toothbrush about every three months.How often you replace your toothbrush depends, of course, on how often you use it. We recommend, strongly, that you brush at least twice a day. If you’re brushing twice a day, picking up a new toothbrush at the store every three months is recommended.