How often should you replace a toothbrush?

Why three months

Bristles bend and splay with use, and a bent bristle no longer reaches the gum line, which is the part that matters. Dentists put the useful life at about twelve weeks for normal pressure. If yours look tired after six weeks, you are brushing too hard, not buying bad brushes.

Replace it earlier when

• The bristles splay past the edge of the head.
• You have had a throat infection, flu or a stomach bug: replace it once you are better.
• Someone else used it by mistake.
• It fell in the sink, or worse, behind the toilet.

Electric heads are the same

Every three months, and the small round heads often wear faster because they take the full load. Many have blue bristles that fade to white as a reminder, which is the one bit of packaging design that actually helps.

Where it stands matters

Upright, in the open, so it dries between uses. Not in a closed cup, not in a travel cap at home. Keep it a metre from the toilet if the bathroom allows, and close the lid when you flush.

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