牙根部覆盖着牙髓，它比牙釉质更易磨损。
The root is covered with cementum, which is worn away more easily than enamel.
目的 利用天然牙的牙根放置自行研制的球帽型附着体，增强覆盖义齿的固位力。
Objective Using stud type attachments on the natural root in order to get retention for overdentures.
结果表明：（1）岸杂一号狗牙根种苗在入冬前覆盖稻草、猪粪渣、火土灰和黄泥，种苗由自然条件下越冬率40％分别提高到98％、95％、95％和65％。
The results showed that (1) the survival rate of seedling increased by. 98% , 95% , 95% and 65% from the natural 40% by covering with rice straw, hog dung, ash soil and loess respectively;
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