ABSTRACT
BACKGROUND:Domestic scholars use the potentiodynamic polarization technique to determine the corrosion potential of the dental aloys, which is used to evaluate the corrosion performance of the lownoble metal. They have discovered that the main reason affecting corrosion resistance is the content of noble metal. OBJECTIVE:To evaluate the corrosion resistance of Ti, Au aloy, Co-Cr aloy, Ti aloy, and Ni-Cr aloy. METHODS: Five aloys were immersed in synthetic saliva solution. The corrosion potential and corrosion current density of the aloys were determined with potentiadynamic polarization technique. RESULTS AND CONCLUSION:The galvanic series of five kinds of aloys were ranged as folows: Au aloy > pure Ti > Ti aloy > Co-Cr aloy > Ni-Cr aloy. Au aloy and pure Ti had more positive potential that were not easy to produce corrosion; Ti aloy and Co-Cr aloy could form stable oxidation film with a strong ability of anti-pitting and crevice corrosion; Ni-Cr aloy potential was more negative and easy to be dissolved. The corrosion current density of five kinds of aloys was ranged as folows: Au aloy < pure Ti < Ti aloy < Co-Cr aloy < Ni-Cr aloy. Au aloy and pure Ti had lowest current density which was 10-8, indicating that the corrosion rate of Au aloy and pure Ti was lower; in contrast, Ni-Cr aloy possessed the maximum corrosion rate. These findings indicate that Au aloy and pure Ti exhibit a very high corrosion resistance. The corrosion rate of Ni-Cr aloy is the highest; therefore, Ni-Cr aloy is the least acceptable material for implant suprastucture.
ABSTRACT
Objective To investigate the effect of apoptosis-related gene p53 on the apoptosis of retinal capillary cells in rats with spontaneously hypertensive (SHR) after ischemic reperfusion injury. Methods A total of 60 SHR rats were randomly divided into sham group (SHR-SH) and retinal ischemie reperfusion group (SHR-RIR), which were subdivided into 5 subgroups according to the time after RIR: 2, 6, 24, and 72 hours and 7 days, with 6 rats in each subgroup. Another 60 Wistar-Kyoto (WKY) rats were divided into the same groups as the SHR rats as the control. The RIR model was set up. The apoptosis of retinal capillary cells was detected by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) methods and the expression of p53 was determined by streptavidin-perosidase (SP) immunohistochemistry. Results The apoptosis rate of retinal capillary cells in the 5 SHR-RIR groups was (8.64±0.56)%, (14.92±0.99)%, (24.72±2.98)%, (16.53±1.80)%, and (7.12±1.10)%,respectively. The expression of p53 in SHR-RIR groups increased at the 2nd hour after RIR, reached the peak at the 24th hour, kept the high level at the 72nd hour, and remained a little at the 7th day, which was significantly different from which in the SHR-SH groups (P<0. 01). The expression of p53 were higher in SHR-IR groups than that in the WKY-RIR groups (P<0. 01). Conclusions p53 may play a part in RIR injury by inducing or promoting apoptosis. The apoptosis of retinal capillary cells after RIR is more severe under the hypertension, and reaches the peak at the 24 hour after RIR.