Objective: To study the effect of the modified preparation method with root canal flushing of different solutions on the anti-fracture properties of mechanical nickel-titanium filings. Methods: A transparent resin model of root canal was established. ProTaper Universal (PTU F1) instrument was used to prepare the root canals. The number of prepared root canals by each PTU F1 with the various solutions(n = 20) was recorded and compared among groups. Results: 6. 13 ± 3. 52 root canals were prepared in distilled water group, 6. 25 ± 1. 76 in 0. 9％saline group, 6. 27 ± 2. 07 of 0. 2％ chlorhexidine group, 6. 88 ± 3. 21 in 1％ sodium hypochlorite group, 4. 31 ± 2. 34 in 5％ sodium hypochlorite group and 3. 26 ± 2. 08 in dry drilling group. The number between each 2 of distilled water, 0. 9％saline group, 0. 2％chlorhexidine group and 1％ sodium hypochlorite group, and the number between 5％ sodium hypochlorite group and dry drilling group was not statistically significant(P＞ 0. 05). The number of prepared root canals in the first 4 groups was more than that in the latter 2 groups(P＜ 0. 05). Conclusion: Distilled water, 0. 9％ saline, 0. 2％ chlorhexidine or 1％ sodium hypochlorite for root canal irrigation can improve mechanical nickel-titanium instrument for fatigue resistance in root canal preparation, but 5％ sodium hypochlorite and dry drilling can not.

Objective To summarize clinicopathologic features of papillary thyroid carcinoma (PTC) coexistent with chronic lymphocytic thyroiditis (CLT) and investigate risk factors for lymph node metastasis.Methods The medical records of 4 264 consecutive papillary thyroid carcinoma patients who received surgical treatment from Oct 2013 to Oct 2015 in Peking Union Medical College Hospital were reviewed.The diagnoses was confirmed by histopathological tests.Univariate analysis was performed to identify specific clinicopathologic features of PTC with CLT.Univariate and multivariate analysis were performed to determine whether each clinicopathologic feature was an independent risk factor for lymph node metastasis.Results In all 4 265 cases,there were 3 059 papillary thyroid microcarcinoma (PTMC) (71.7％),1 010 PTC patients (23.7％) with CLT.909 female patients (90％),624 cases with multifocal lesions (61.8％),422 cases with extra-thyroid extension (41.8％),429 cases with lymph node metastasis (42.5％),and 133 cases with metastatic lymph nodes(LNs) ≥6 (13.2％).The median age was 43 years old and median tumor size was 0.8 cm.Patients with CLT were more females (90.0％ vs.70.2％;P ＜ 0.001),younger median age (43 vs.44 years;P =0.001),and lower incidence of lymph node metastasis (42.5％ vs.50.9％;P ＜0.001).CLT was not associated with tumor size,multifocal lesions,extra-thyroid extension and metastatic LNs≥6 (0.8 cm vs.0.7 cm,61.8％ vs.62.9％,41.8％ vs.42.1％ and 13.2％ vs.14.8％,respectively,all P ＞ 0.05).In multivariate analysis,CLT was an independent protective factor for lymph node metastasis (OR =0.713,95％ CI 0.609-0.835,P ＜0.001).In PTC patients with lymph node metastasis,CLT was not associated with lymph node metastasis number (3 vs.3,P =0.300).Conclusions Chronic lymphocytic thyroiditis was an independent protective factor for papillary thyroid carcinoma patients with lymph node metastasis.But in patients with lymph node metastasis,the metastatic number didn't decrease.