They suggest limiting the length of tooth-brushing to two minutes and a force of 150 grams.

研究人员建议，刷牙的时间应该是两分钟，力度应在150克左右。

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Tooth brushing became popular during the World War I.

第一次世界大战期间，刷牙开始流行起来。

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Poor tooth brushing techniques can harm your teeth - if you really scrub your teeth too hard, you will wear the sides of your teeth down, leaving V-shaped defects near the gum margins.

不恰当的刷牙方法会损害牙齿，如果你真的太用力刷牙，就会磨损牙齿边缘，在牙龈缘附近形成V字形缺口。

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At the same time, Scotland's chief dentist urged parents to ensure their children stuck to a good tooth-brushing routine.

BBC: Scottish children's teeth 'best on record'

Creating routines or even rituals around our work helps in the same way making a routine out of tooth-brushing or taking daily walks helps in everyday living.

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