Objective: To evaluate the effect of core∶dentin thickness ratio on the flexure strength, fracture mode and origin of bilayered IPS Empress Ⅱceramic composite specimens. Methods: IPS EmpressⅡ core ceramic, dentin porcelain and bilayered composite specimens with core∶dentin thickness ratio of 2∶1 and 1∶1 were tested in three-point flexure strength. Mean strengths and standard deviations were determined. The optical microscopy was employed for identification of the fracture mode and origin. Results: The flexure strength of dentin porcelain was the smallest (62.7 MPa), and the strength of bilayered composite specimens was smaller than single-layered core ceramic(190.2 MPa). The core∶dentin ratio did not influence the strength of bilayered composite specimens. The frequency of occurrence of bilayered specimen delaminations was higher in the group of core∶dentin thickness ratio of 1∶1 than in the group of 2∶1. Conclusion: IPS Empress Ⅱcore ceramic was significantly stronger than veneering dentin porcelain. Core∶dentin thickness ratio could significantly influence the fracture mode and origin, and bilayered IPS Empress Ⅱceramic composite specimens showed little influence in the fracture strength.

OBJECTIVE：To study the improvement effects of saf flower yellow on lung function in chronic obstructive pulmonary disease （COPD）model rats. METHODS ：SD rats were randomly divided into control group ，model group ，positive control group （dexamethasone，0.09 mg/kg），safflower yellow low-dose ，medium-dose and high-dose groups （5，10，20 mg/kg）， with 10 rats in control group and 11 rats in other groups. Except for control group ，other groups were given lipopolysaccharide combined with fumigation to induce COPD model. After modeling ，control group and model group were given constant volume of normal saline intragastrically ，and administration groups were given relevant medicine intragastrically ，once a day ，for consecutive 12 weeks. After last medication ，the levels of TNF-α，IL-6 and IL- 8 were detected by ELISA. The levels of blood gas indexes （PaO2，SaO2 and PaCO 2）in whole blood were detected by blood gas analyzer. The levels of lung function indexes （FVC，FEV1， FEV1/FVC，PEF and MMEF ）were detected by lung function analyzer. The expression of TLR 4，NF-κB and I κB-α protein were detected by Western blot. HE staining was used to observe the pathological changes of lung tissue. RESULTS ：Compared with control group ，the serum levels of TNF-α，IL-6 and IL- 8，the level of PaCO 2 in whole blood as well as the protein expression of TLR4 and NF-κB in lung tissue were increased significantly in model group（P＜0.01）；the levels of PaO 2 and SaO 2 in whole blood，the levels of lung function as FVC ，FEV1，FEV1/ FVC，PEF and MMEF as well as the protein expression of IκBα in lung tissue were decreased significantly（P＜0.01）； there were obvious degeneration and necrosis in the epithelial cells of lung tissue ，and obvious inflammatory infiltration in the interstitial cells. Compared with model group ，the levels o f inflammatory factors in serum ，blood gas indexes in whole blood and lung function indexes as well as the expression of related protein in lung tissue （except for IκBα in low-dose group）were reversed significantly in safflower yellow groups （P＜0.05 or P＜ 0.01）；the necrosis ，exfoliation and inflammatory infiltration of epithelial cells in lung tissue were improved in varying degrees. CONCLUSIONS：Safflower yellow can significantly improve the lung function of COPD model rats ，and its mechanism may be related to inhibiting the expression of inflammatory factors and regulating the expression of TLR 4/NF-κB pathway-related proteins.