Likely cause: Known as bruxism, teeth-grinding varies from jaw clenching to ferocious grinding that wears teeth down to stumps. It is usually due to genetics or stress.

可能的诱发原因：虽说都叫磨牙症，但磨牙的情况各不相同，从牙关紧闭到疯狂磨牙直到牙齿只剩残根。磨牙通常是由遗传或压力造成的。

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If you often wake up with a dull headache or sore jaw, you may be grinding your teeth or clenching your jaw while you sleep, a problem called bruxism.

如果你经常醒来的时候有轻微的头痛或下巴肿痛，你可能是在睡觉的时候磨牙或者紧闭牙关，被称为夜间磨牙症。

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Your dentist will fit you with a device that prevents your jaw from clenching.

你的牙医会用一个设备来阻止你紧闭牙关。

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She wasn't eating. She had terrible stomach pains. She started clenching her jaw and grinding her teeth at night.

VOA: special.2010.04.22

Her only visible reaction was the clenching and unclenching of her jaw.

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