A tired toothbrush looks like it tried to hug every tooth at once. Once bristles flare, they stop cleaning the gumline well.
So what is the honest answer?
Replace a toothbrush about every three months, sooner if the bristles splay or you were sick.
Three months is a good default. Heavy handed brushers may need sooner. Electric heads follow the same idea. After a stomach bug or nasty respiratory infection, I replace mine because it is cheap peace of mind.
The part people usually miss
Store it upright, let it dry, and do not cap a wet brush all day. If bristles flatten quickly, that is a pressure problem, not a brush problem.
My rule is boring and useful: change one thing, watch what happens, and stop if your mouth gets irritated. Teeth respond better to steady habits than to panic routines before weddings, photos, or dentist appointments.
How I would handle it this week
- Take a baseline photo in bathroom lighting you can repeat.
- Keep brushing gentle at the gumline, soft bristles only.
- Do not stack three new products at once, because then you cannot tell what helped or hurt.
Related reading: this guide and this review or article both go deeper on the practical side.