牙结石—如果菌斑呆的时间足够长，它就开始矿化变硬形成牙石或牙垢，因为菌斑从唾液中吸收了钙，磷和其他矿物质。

Calculus - If left alone long enough, plaque begins to mineralize and harden into calculus or tartar because the plaque absorbs calcium, phosphorus and other minerals from saliva.

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牙结石—如果菌斑呆的时间足够长，它就开始矿化变硬形成牙石或牙垢，因为菌斑从唾液中吸收了钙，磷和其他矿物质。

Calculus - If left alone long enough, plaque begins to mineralize and harden into calculus or tartar because the plaque absorbs calcium, phosphorus and other minerals from saliva.

youdao