Frequency of changing your toothbrush is dependent on so many factors: how hard you brush, how often you brush, if someone else uses your brush, if you brush more than two times a day, what type of pastes are you using, how it's stored, have you been sick recently, if someone has the same color brush as you, has it been contaminated, how long has it been in your bathroom, and so on and on..
Blah, blah, blah. Every 3 months--that's all you need to know--or whenever you cannot see the sides of the toothbrush because the bristles are too frayed.
Here are some quarterly events to help you remember when to change your toothbrush:
HOLIDAYS
SCHOOL EVENTS
SPORTS CHAMPIONSHIPS
SEASONS
THE 4 TIMES A YEAR THE HUSBAND DOES THE DISHES WITHOUT BEING ASKED
...Wow, so proud. Reward please!
The brush is completely ineffective once the bristles are frayed. This is usually after 3 months. Just change it out.
Brush softly and carry a big stick. --Dr Pearl E. Whites