Do I only need to replace my toothbrush once the bristles splay? When is the right time to change it?

It is best to replace your toothbrush every 2 to 3 months even if the bristles have not splayed. The bristles lose their resilience with use, so cleaning becomes less effective, and bacteria build up between them. If the bristles have splayed, replace it right away regardless of how long you have used it. However, if they splay within a month, that is a sign you are brushing too hard and your technique needs review; we also recommend replacing your brush after an illness such as a cold.