Objective: To study the microstructure development of mandibular bone in rats on timing sequence and under different occlusal force. Methods: 63 male SD rats aged 23 days were randomly divided into three groups (n = 7): Baseline group, soft-diet (SD) group and hard-diet (HD) group. 7 rats were killed at week 0, 2, 4, 6 and 8 respectively after feeding the food with different hardness.Micro-CT was used to reconstruct and analysis microstructure of the region of interest in mandible of the rats. Results: Compared with HD group, bone volume/total volume (BV/TV) and trabecular thickness (Tb. Th) decreased significantly after 4 th week (P ＜ 0. 05), the bone surface/bone volume (BS/BV) and trabecular separation (Tb. Sp) increased significantly during the 4 th to the 6 th week (P ＜0. 05) . Conclusion: In the process of mandibular development in rats, reduction of occlusal force may lead to reduction of bone mass, and the changes of microstructure are closely related to the time of intervention.

Objective To analyze the risk factors of multi-drug resistant organism (MDRO) infection after liver transplantation. Methods The clinical data of 77 recipients undergoing liver transplantation were retrospectively analyzed. According to the incidence of MDRO infection, all recipients were divided into the non-MDRO infection group (n=51) and MDRO infection group (n=26). The infection rate and strain distribution of MDRO in liver transplant recipients were summarized. The risk factors of MDRO infection in liver transplant recipients were identified. Clinical prognosis of all recipients was statistically compared between two groups. Results The infection rate of MDRO after liver transplantation was 34% (26/77), mainly carbapenem-resistant MDRO infection. The main sites of infection included lung, abdominal cavity and incision. Univariate analysis showed that postoperative tracheal intubation ≥48 h, length of intensive care unit (ICU) stay ≥72 h, length of hospital stay ≥30 d, re-operation, continuous renal replacement therapy (CRRT) and tacrolimus (Tac) blood concentration ≥15 ng/mL were the risk factors for MDRO infection after liver transplantation. Cox regression analysis indicated that postoperative tracheal intubation≥48 h, re-operation, CRRT and Tac blood concentration ≥15 ng/mL were the independent risk factors for MDRO infection after liver transplantation. The fatality in the MDRO infection group was significantly higher than that in the non-MDRO infection group [31%(8/26) vs. 10%(5/51), P=0.01]. Conclusions Postoperative tracheal intubation ≥48 h, re-operation, CRRT and Tac blood concentration ≥15 ng/mL may increase the risk of MDRO infection after liver transplantation and affect clinical prognosis of the recipients.