BACKGROUND:In the fluorine-containing acidic environment, it is unclear whether Damon copper- nickel-titanium arch wire can have a corrosion resistance similar to conventional nickel-titanium arch wire and whether copper ion wil affect its corrosion resistance. OBJECTIVE: To evaluate the corrosion resistance of 3M nickel-titanium arch wires and Damon copper-nickel-titanium arch wires in artificial saliva with different fluoride and pH. METHODS:Potentiodynamic polarization curves of 3M nickel-titanium arch wires and Damon copper-nickel-titanium arch wires were measured in four kinds of artificial saliva (pH=7; pH=7, 0.2% fluoride; pH=7, 0.5% fluoride; pH=5, 0.5% fluoride). Then, the corrosion potential, corrosion current density and polarization resistance were acquired, and scanning electron microscope was used for morphological observation after corrosion. RESULTS AND CONCLUSION: In neutral (pH=7) artificial saliva, 0.2% fluoride ions added could shift up the Damon specimen polarization curve, increase the corrosion cerrent density and reduce the polarization resistance (P < 0.05); under the scanning electron microscope, corrosion was observable on the specimen surface. But 3M specimen polarization curve did not move, corrosion current density and polarization resistance substantialy unchanged (P > 0.05), and no significant corrosion was produced. When fluoride concentration was increased to 0.5%, the polarization curves of two kinds of the specimens moved, the corrosion cerrent density increased, the polarization resistance decreased (P < 0.05), and there was significant presence of corrosion on the specimen surface. When pH=5, corrosion phenomenon was more pronounced. These findings suggest that low concentrations fluoride cannot affect corrosion resistance of 3M arch wire, but can reduce the corrosion resistance of Damon arch wire; high concentrations of fluoride and acid can both reduce their corrosion resistance. In addition, the corrosion resistance of 3M arch is stronger than that of Damon arch wire.

Objective To analyze the MRI characteristics of cavernous angioma of the epidural space in spine.Methods MR imaging features of cavernous angioma of epidural space in 3 cases confirmed by surgery-pathology were analysed with literature review . Results Among the three cases,the tumors located in the lumbar spine in one and in the thoracic spine in 2.The tumors were all at posterior to the spinal cord and shuttle-shaped,the major axis was consistent with the spinal ordinate axis,the corresponding plane spinal cords were compressed and resulting in distortion and shift.The tumors were high signal intensity on T_2WI,and obviously homogeneous enhanced after Gd-DTPA administration. Conclusion MRI examination is the best method to diagnose this kind of disease.

Objective To explore the characteristic findings of 1H-MR spectroscopy(1H-MRS) in the prefrontal cortex and amygdala of patients with heroine dependence(HD), and the relationship to total cumulative dose of inhaled heroine.Methods Fourteen male HD patients and 12 healthy controls (HC) underwent 1H-MRS at the prefrontal cortex and amygdala regions.The total cumulative in haled heroin dose was (852±341) g in HD.Ratios of N-acetylaspartate/creatine(NAA/Cr) and choline/creatine (Cho/Cr) were respectively measured in the prefrontal cortex and bilateral amygdale regions.The student's t test and the linear correlation were employed for statistical analysis.Results Compared to HC group, HD patients had a significant lower ratio of NAA/Cr in the prefrontal cortex (1.44±0.46 vs 1.50±0.75, t=1.77 ,P <0.05), left amygdala region (1.32±0.08 vs 1.42±0.08, t=3.41, P < 0.05), and right amygdala region (1.34±0.09 vs 1.44±0.10, t=2.63, P <0.05), the HD patients had a significant increased ratio of Cho/Cr in the prefrontal cortex (0.92±0.06 vs 0.86±0.08, t=2.31, P < 0.05), left amygdala region (1.20+0.12 vs 1.07±0.04, t=3.60,P<0.05) and right amygdala region(1.26±0.15 vs 1.12±0.11,t=2.60,P <0.05).There was a negative linear correlation between the total cumulative inhaled heroine dose and the ratio of NKA/Cr in the prefrontal cortex (r=-0.9159, P < 0.01), left amygdala region (r=-0.8756, P < 0.01), and right amygdala region (r=-0.9399, P < 0.01) respectively.Conclusions The study indicates that neuronal damage and glial proliferation may occur in the prefrontal cortex and amygdala region, which suggests the abnormalities of executive function and emotion in patients with HD.A relationship exists between the heroin-induced metabolic abnormality and the total cumulative dose of inhaled heroine.

Objective To study the value of~1H-magnetic resonance spectroscopy(~1H-MRS) and diffusion weighted imaging(DWI) in evaluating the changes of pathological structures of hippocampal sclerosis.Methods Twelve normal controls and twelve cases with temporal lobe epilepsy were examined by conventional MRI,~1H-MRS and DWI.The NAA/(Cr+Cho) ratios and ADC values in the hippocampus were measured and compared between patients and normal controls.Results The NAA/(Cr+Cho) ratios of hippocampus in patients with hippocampal sclerosis were significant decrease in comparison with controls and the contralateral side,and the ADC values were also significant increase.There was correlation between the NAA/(Cr+Cho) ratios and ADC values in the disordered hippocampus(r=-0.79,P=0.002).Conclusion There is a significant correlation between the NAA/(Cr+Cho) ratios and ADC values in the hippocampal sclerosis.~1H-MRS and DWI capture partially complementary aspects of hippocampal pathology noninvasively in vivo.

Objective To investigate the effect of electromagnetic wave power density on the expression of glial fibrillary acidic protein(GFAP)in the hippocampus of SD rats under 1800 MHz electromagnetic wave irradiation,and whether it exhibits a"window effect".Methods Ninety-eight 4-week-old SPF-grade SD rats were randomly divided into 14 groups,with 7 rats in each group.Seven groups were exposed groups(frequency:1800 MHz,power densities:0.1 mW/cm2,0.3 mW/cm2,0.5 mW/cm2,0.7 mW/cm2,0.9 mW/cm2,1.0 mW/cm2,1.2 mW/cm2)and corresponding 7 groups were control groups(power density:0 mW/cm2).Exposure was conducted for 12 hours daily for 3 weeks.After exposure,Western Blot was used to detect the expression level of GFAP in the hippocampal tissue,and immunohistochemistry staining was performed to determine the average optical density(MOD)value of GFAP-positive expression products in the DG,CA3,and CA1 regions of the hippocampal tissue,to determine the power density window of GFAP expression in the hippocampus of SD rats under 1800 MHz exposure.Results At power densities of 0.1 mW/cm2 and 0.3 mW/cm2,Western Blot results showed increased expression of GFAP in the rat hippocampus(P<0.05),and immunohistochemistry staining demonstrated increased MOD values of GFAP in the three regions(P<0.05).Conclusion Long-term exposure to 1800 MHz elect-romagnetic radiation has a"window effect"on the expression of GFAP in the DG,CA3,and CA1 regions of the hippocampus in SD rats,with power density windows of 0.1 mW/cm2 and 0.3 mW/cm2.