Objective: To observe the effects of acid etching times on nano-leakage and microtensile bond strength(?TBS) of the 4 total-etching adhesives-dentin bond.Methods: Superficial occlusal dentin surfaces of 80 molars were prepared with 600-grit SiC paper under running water.4 adhesives were applied to dentin surfaces under different etching time.The bonded teeth were sectioned occluso-gingivally into 1.0 mm?1.0 mm?4.0 mm serial slabs which were prepared for TEM and ?TBS tests.Results: Under 15 s etching time for 4 adhesives,the highest ?TBS(OB(25.36?4.18) MPa,SB(24.25?3.97) MPa,OS(28.65?4.93) MPa,PB(27.12?4.13) MPa) were achieved,and the amount of nanoleakage was positively correlated with the length of etching time.Conclusion: Etching for a reasonable time demineralizes the dentin surface to a moderate depth,resulting in higher ?TBS and lower nanoleakage.

Objective: To study the effect of cementation materials on the fracture resistance of metal free premolar Artglass crown. Methods: Thirty extracted human maxillary premolars were regularly prepared for cementation. Artglass crowns were cemented onto the teeth with zinc phosphate cement (ZnP), glass ionomer cement(GIC)or a resinous cement in combination with a dentinal bonding agent. Each of the cementation material was applied in 10 premolars. Artificial crowns were vertically loaded until the Artglass crowns compressed to failure. Significant differences of fracture loads between experimental groups were assessed by paired t test. Results: The fracture load(N) of ZnP, GIC and resinous cement were 1 743.1 ?383.4, 1 682.4?613.7 and 2 226.9?270.1 respectively( P

Objective:To test the effects of different preparation methods on the shear bond strength between porcelain veneers and the brackets.Methods:48 metal-porcelain veneers were randomly and evenly divided into two groups. The veneers in group 1 were grinded with stone, while others were intact. The veneers were bonded by acid etching,silicone coupler and acid etching combined with silicone coupler respectively.After bonding and 500 thermo cycle treatment, all veneers were submitted to shear bond strength test and the incidence of porcelain fracture was recorded.Results:The shear bond strength of the grinded samples was higher than that of the intact(P

Objective: To compare the fracture resistance of pulpless teeth restored with three types of post core.Methods: A total of 21 recently extracted sound upper incisors were randomly distributed into 3 groups. In group A the teeth were restored with prefabricated glass fiber post and composite core; in group B with custom cast titanium alloy post and core; and in group C with Ni Cr alloy dowel core. The size and shape of posts were identical in the 3 groups. All teeth were fully covered with Ni Cr alloy cast crown. Fracture resistance was measured by applying a point force at 130 degrees to the long axis of the teeth. Results: Mean fracture threshold was (276.6?15.1)N in group A, (394.7?29.1)N in group B and (373.4? 53.8 )N in group C. In group B and C, however, fracture always affected the tooth itself,whereas in group A,the core always failed first. Conclusion: Fiber reinforced composite(FRC) post may meet the clinical need, FRC post combined with composite core may prevent tooth root from fracture.

Objetives: To evaluate the microtensile bond strengths o f four dentin adhesives (Single Bond, Bond-1, Prime&Bond NT and One-Step) i n vivo.Methods: Before extraction the superficial occlu sal dentin of 19 molars (because of severe periodontitis) in 17 volunteers was exposed by diamond bur of a high-speed hand-piece copious air-water spray under local anesthesia, the crown was bonded with one of the above adhesives a ccording to the manufacturers' instructions. The teeth were then extracted and kept in normal saline for 24 h under 37 ℃,sectioned to obtain two or three bar -shaped specimens, which were then shaped to an hour-glass form. The specimens were stressed until rupture of the bond. The mean bond strength of the adhesive s was measured and compared using student test. Rusults: M ean microtensile bond strength (MPa) of Single Bond,Bond-1,One-Step and Prime & Bond NT to the tooth surface was 26.18?3.67,30.08?3.15,29.91?3.51,29.70?3 .03 respectively (P

Objective To speculate the contents changes and clinical significance of heme oxygenase-1(HO-1) and unconjugated bilirubin (UCB) in the patients with acute cerebral infarction.Methods HO-1 and UCB in blood serum were measured in these patients with acute cerebral infarction(ACI) and control group at one day, third day,and sixth day after the onset by ELISA and oxidation of vanadate. Results The content of HO-1 and UCB in serum decreased step by step at the first day, third day, and sixth day after the onset. The level of HO-1 displayed a positive correlation with the UCB in serum in the first day after the onset (r=0.645, P

AIM: To observe the changes of Ca-L current (ICa-L) and to investigate the mechanism of salvia miltiorrhizae (SM) for eliminating Ca~2+ overloaded in cells during acute hypoxia/reoxygenation. METHODS: The whole cell patch clamp technique was applied to study the changes of ICa-L. Different concentrations (32, 320, ~3 200 mg/L) of SM were added to the ventricular myocytes isolated from guinea pigs by enzyme digestion. RESULTS: SM (32, 320, ~3 200 mg/L) decreased the amplitude of ICa-L in a concentration-dependent manner regardless of these cells were under normoxia, hypoxia or reoxygenation. Furthermore, SM at low concentration (32 mg/L) was more effective to hypoxia or reoxygenation-treated cells than that to the cells under normoxia condition. CONCLUSION: These results indicate that SM effectively decreases the abnormal raised amplitude of ICa-L in ventricular myocytes under hypoxia or reoxygenation conditions, preventing Ca~2+ overloaded in the cells. [

Objective To identify the factors related to the influence of medical research papers. Methods The influence of 1146 research papers by the hospital in the period 1996-2003 and its relationship with such factors as the backgrounds of the authors and the quality of the papers were studied u-sing regression analysis. Results Nine factors, including the impact factor, the status of the paper (being or not being one based on fund-supported research or representing research achievements), and the status of the author (being or not being chosen for talent cultivation and undertaking or not undertaking research projects), were significantly correlated with the influence of the papers. Conclusion In order to enhance the influence of medical research papers, it is necessary for research' management departments not only to encourage research personnel to publish papers in journals with high impact factors but also to step up efforts to better personnel cultivation, degree education, and project and achievement management so as to set up a quality and distinguished research contingent.

Objective:To measure the effect of disinfection on dimension stability of four high polymer impression materials which were separately immersed in 20 ml/L glutaraldehyde solution.Methods:Fifteen plaster replication models of four high polymer impression materials(Impregum Penta polyether, Express-Putty silicone, Silagum-Putty silicone, GC EXAFINE silicone) were made on the same metal master cast respectively. Vertical and horizontal dimensions between landmarks on the masters and plaster casts were measured with an optical microscope,one-way ANOVA was used to compare the measurements among the materials.Results:The difference between the masters and Casts in horizontal distances measured on Express-Putty silicone impression material produced models was longer than those on other high polymer impression materials produced ones after disinfection for 20 minutes and beyond clinical requirement. Compared with metal master cast, the difference became significant when these four silicone impression materials were disinfected for 40 minutes. Conclusion: Among the four kinds of impression materials, the Express-Putty silicone material is relatively the most accurate one after disinfection for 20 minutes.

Objective:In order to optimize the crystallization technics, the effects of heat-treatment on the flexible strength and microstructure of a novel dental mica glass-ceramic were studied in present study. Methods:7 groups were treated respectively with different crystallization temperature and different crystallization time.Then the flexible strength, X-ray diffraction (XRD)and scanning electron microscope(SEM) were used to study the flexible strength and microstructure of such a novel dental mica glass-ceramic. Results: The result of the study indicated that along with the rise of crystallizing temperature and crystallizing time, this dental mica glass-ceramic showed the peak of bending strength (173.68 MPa) at 680 ℃ for 120 min.Conclusion:This material is promising as esthetic all-ceramic dental material.