头牙

一次性双吸引器头牙种植骨收集器的制作和应用

Head continuous with body ; The production and application of a one-off bone collector with two suction tips using in dental implantation

目的：介绍自行研制的一次性双吸引器头牙种植骨收集器的制作并检测收集物的体积和含量。

Objective : To introduce a one-off bone collector with two suction tips designed by us and to determine the amount and component of bone harvested from dental implant osteotomies .

GB/T5785-1986六角头螺栓细牙A和B级

Hexagon head bolts-Fine pitch thread-Product grades A and B

不要把我折磨得跟你自己一样地发疯吧，他叫，扭开他的头，咬着牙。

` Don 't torture me till I am as mad as yourself , ' cried he , wrenching his head free , and grinding his teeth .

有时候起了狂风，把他打得出不来气，可是他低着头，咬着牙，向前钻，像一条浮着逆水的大鱼；

Sometimes there would be a raking wind which beat the breath out of him ; but he would lower his head , grit his teeth and forge doggedly ahead , like a large fish swimming against the current .

二叠纪动物群繁盛，大量的动物化石大多采自泥岩和灰岩，计有138属421种，主要包括（？）、腕足、双壳类、头足类和牙形刺等。

The Permian faunas are very abundant , with a great of fossils , mostly collected from the mudstone and limestone . They consist of 421 species and 183 genera , mainly including Fusulinids , Brachiopoda , Bivalves , Cephalopoda , Conodont and so on .