19 cases with fractured instruments in root canals of posterior teeth were selected.The coronal 1-2 mm of the fractured instrument was exposed under microscope with ultrasonic technique.Irs instrument was used to clamp the end of the fractured instrument,then the fractured instrument was extracted.12 fractured instruments were removed by irs instrument successfully.The success rate was 63%,and the mean time consuming was 65 min.No root canal perforation happened.7 fractured instruments were removed by ultrasonic instruments,and the mean time consuming was 115 min.2 root canal perforations happened.The irs is an effective instrument for removal of separated instruments in root canals.

【Objective】 To explore pain and collapse mechanisms in fosteonecrosis of the femoral head (ONFH) with bone marrow edema (BME). 【Methods】 ONFH patients at ARCO Ⅲ stage who underwent total hip arthroplasty in the First Affiliated Hospital of Guangzhou University of Chinese Medicine were enrolled; the femoral head samples, clinical and imaging data were collected. These patients were divided into BME group and non-BME group according to the MR data in one week preoperative. Hematoxylin-eosin and Sirius red staining were performed to observe the morphological changes in bone tissue of femoral head specimens. Western blotting and qPCR were used to semi-quantitatively analyze the expression levels of CTSK, RANKL, and Netrin-1 proteins and mRNA in different regions of the bone tissue. 【Results】 Clinical and imaging data showed that ONFH patients with BME had significantly higher scores of VAS than ONFH patients without BME. Hematoxylin-eosin staining showed that bone structure disorder and a large number of empty bone lacunae were found in the necrotic areas in both groups, but there exited significant granulation tissue in the BME group, and spindle-shaped fibroblastic cells and inflammatory cells aggregated in the repaired region. Sirius red staining revealed the necrotic and sclerotic areas were accumulated with many collagenous fiber in the BME group. The results of Western blotting and qPCR showed that Netrin-1 expressions in the necrotic, sclerotic and health areas in the BME group were higher than those in the non-BME group (P<0.05), while osteoclast related proteins and mRNA expressions of the necrotic and sclerotic areas in the BME group was higher than those in the non-BME group (P<0.05). 【Conclusion】 All these findings indicated that hip pain was positively correlated with femoral head necrosis with BME, hyperactive osteoclasts participated in the femoral head collapse with BME, and the upregulated expression of Netrin-1 mediated the pain mechanism.