Open, single center, single arm test design. Plan to enroll 24 subjects. On the basis of clinical standard treatment, the injection of dental mesenchymal stem cells was increased on day 1, 3 and 7 of the trial.
Injection dose: 1.0x106 cells /kg. Injection method: slowly and quietly drop 50 mL of normal saline, then the endodontic mesenchymal stem cell injection (after 60 min), and then 50 mL of normal saline.
