Toothbrushes are generally replaced once every three months or so. When using a toothbrush, the bristles should be as close to the tooth surface as possible, reaching into the gingival sulcus to clean the plaque on each tooth surface. Widening the gap of the bristles will weaken the cleaning effect, resulting in toothpaste or food residue, soft dirt, etc. being retained at the root of the bristles. When the bristles are obviously bent, deformed or collapsed, it means that too much force is exerted and the toothbrush is worn out and cannot continue to clean, so it should be replaced in time. When the residue accumulated at the bottom of the bristles accumulates slowly and cannot be completely removed, it will cause bacteria to proliferate and affect oral health, and must be replaced immediately.