Replacing your toothbrush every three months is not without reason. It turns out that even when it looks undamaged, harmful bacteria accumulates in the microdamages of the fibres. It is impossible to rinse all the microorganisms out of the brush – with each brushing they migrate back into the oral cavity. So even if the fibres seem to be as good as new, if you have used the brush for a few weeks, replace it. For the health of your teeth.