Comment by plausibility
Comment by plausibility 7 days ago
The usual problem with toothbrush bristles is they become microscopically worn down, so they don't scrape off plaque as effectively. Even if you can't see the problem, it might not be working as well as a fresh head will.
You can find electron microscope scans of fresh toothbrushes and worn ones in this[0] Applied Science YouTube video.