| 摘要 |
PROBLEM TO BE SOLVED: To finish tooth-brushing in a short period. SOLUTION: The length of bristle of a toothbrush is set to 5 to 9 mm for an adult, and 3 to 5 mm for a child, and while allowing the bristle tips to reach an interdental part and a recess, the dirt of teeth can be efficiently removed in a short time.
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