After 7days,the group A1 and B1 were prepared for canal post,group A2 and group B2 were left untreated.

• B组20颗牙根管制备后Ther-mafil热熔牙胶充填,7d后,10颗牙行桩的根管制备为B1组,10颗牙留作对照为B2组。