早在公元前3500年，巴比伦人咀嚼枝条，这似乎是牙刷的起源。
The toothbrush seems to have its origins in the chewing sticks of Babylonia as early as 3500 BC.
为了清洁牙齿切端或咬合面(咀嚼食物的那一面)握牙刷是刷毛与这些面垂直。
To clean the biting or chewing surfaces of the teeth, hold the brush so the bristles are straight down on those surfaces.
当你咀嚼清脆的水果和蔬菜时，它们起着小牙刷的作用。
Crunchy fruits and vegetables act as little toothbrushes when you chew them;
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