上下颌一、二磨牙,在完成咀嚼功能上,有着非常重要的作用。因龋病或外伤,使牙冠丧失80%以上,或仅存在较健康的牙根时,仍需采用某些特殊的医疗技术措施,以求此类残根或残冠得到永久性保存,在此基础上,施行除髓术及根管治疗术后,采用根管内插入螺旋根钉,并用无缝带环,银汞充填形? Upper and lower jaw one or two molars, in the completion of chewing function, has a very important role. Due to dental caries or trauma, the loss of more than 80% of the crown, or the existence of only healthy roots, the need to use some special medical and technical measures, such residual roots or crown to be permanently preserved in this Based on the implementation of the removal of pulp surgery and root canal therapy, the use of root canal insertion screw root nails, and seamless belt loop, amalgam filling shape?