钻头有哪几种?
参考答案:
钻头有麻花钻、扁钻、中心钻等。
牙槽骨水平吸收时形成的牙周袋通常为()
A.骨上袋
B.骨内袋
C.复杂袋
D.一壁骨袋
E.四壁骨袋
Ordinary people are now lacking of the scientific knowledge about nutrition.
A. short with B. are absent ofC. lack in D. are deficient on