Dental Association recommends: changing out your tooth Brush every 3 months. After normal wear and tear your bristles start to get worn out creating a less effective toothbrush. Clinical studies show that a worn out toothbrush removes less plaque than a new toothbrush. Common sense practices also suggests to replace your toothbrushevery 3 months. It is also a good idea to replace your toothbrush after getting over a illness. Tips of keep you teeth healthy： 1.we should brush teeth twice day . 2.We should have 2 pcs toothbrush for day and night. 3.We should use hard bristle toothbrush for whitening teeth. 4.We should brush you teeth before sleeping. 5.we should changed toothbrush every two month if you want you teeth better than normal."