Evaluate usefulness of longitudinal or thopanotomography in the diagnosis of maxillary-anterior embedded dentes;
上颌骨纵向断层片对上颌前部埋伏牙的诊断价值
A compound punch die made of Cr12MoV steel,hardened at 1040℃ and tempered at 180℃ with an average hardness of 58 HRC,which was used in punching and drawing steel plate with 1mm thickness and stamped into a part like bowl,occurred early longitudinal brittle fracture with service life less than 1000 times.
工作中出现了早期纵向脆断 ,使用寿命不足 10 0 0次。