Your regular toothbrush or electric toothbrush head should be replaced every 3 months, or sooner if the bristles become splayed or flattened.
Once the brush appears splayed, the gentle edges of the bristles are gone, and the jagged edges of the bristles are exposed. Brushing with worn bristles isn’t effective for plaque removal and the jagged edges easily lacerate your fragile gum tissue.
You should replace your toothbrush immediately after any cold or flu-like illnesses to prevent recontamination. The porosities in the toothbrush bristles are ideal for harboring the bugs that cause these illnesses.
Most toothbrushes have indicator bristles that will lose colour which will remind you to add a toothbrush or electric toothbrush head refill to your shopping list.