| ObjectiveCobalt-chromium alloy is widely used in dentistry because of its fine biological compatibility and cheap price. However, when the cobalt-chromium is bedded in oral cavity, it would release heavy metal ions such as chromium ions, which can be absorbed by organs resulting in swollen gums and allergy reaction. Recently, more and more people concerned about the security problem of clinical application of cobalt-chromium alloy. The Co-Cr dental casting alloy applied to the dental restore can be affected by varies complicated factors resulting in the change of metal ions release. This study designs the Co-Cr dental casting alloy size according to the human dental superficial area. This study is aimed to investigate the effect of different factors on the metal ions release of Co-Cr dental casting alloy by in vitro simulating the oral cavity condition such as the changes of pH values, temperature and exposure time. The experimental results provide experimental evidence for the Co-Cr dental casting alloy applied to clinic and proving the corrosion resistance.MethodsThis study adopted Co-Cr dental casting alloy test specimen. The test specimen were put into the artificial saliva with the different pH values of5.0,7.0and9.0, and at different temperature (8℃,37℃,45℃), respectively. The group of pure water was put in the37℃stable temperature culture box. Then the soak solution were measured the chromium ions and cobalt ions concentration by inductively coupled plasma atomic emission spectrometry, ICP-MS at different time point (2w,4w,6w,8w). The data were performed statistical analysis using SPSS13.0statistical software. Results(1) At the pH level of7.0, the Co-Cr dental casting alloy soaked in the artificial saliva and pure water respectively, the concentrations of both the cobalt and chromium ions are higher in the artificial saliva than in the water. The concentrations of two kind of metal ions are both different at different time point, with statistical significance (p<0.05), and there is a significant interaction between artificial saliva and pure water on the release of cobalt and chromium ions from Co-Cr dental casting alloy.(2) Chromium ions release from Co-Cr alloy has time-dependence at37℃temperature with the pH=5.0. Cobalt release from Co-Cr alloy has increased arriving peak at the4th week. Three groupa of different PH values were performed Student Newman Keuls test, any two groups have statistical significant difference (p<0.05), except the groups between PH=7.0andpH=9.0.(3) Both of cobalt and chromium ions release from Co-Cr alloy are different among different temperature. There is a significant difference interaction between pH values and temperature on the release of cobalt and chromium ions from Co-Cr dental casting alloy. At the8th week the speed of chromium ions reach the highest when T=45℃.(4) When the Co-Cr dental casting alloy had been soaking for4weeks, both cobalt and chromium ions release are different among3pH values groups, pH5.0group>pH9.0group>pH7.0group, with statistical significant difference (p<0.05). The concentration of cobalt and chromium ions are both different in different temperature groups, T=45℃group>T=8℃group>T=37℃group with statistical significant difference (p<0.05). There is a significant difference interaction between pH values and temperature on the release of cobalt and chromium ions from Co-Cr dental casting alloy, with statistical significance (p<0.05).(5) The mass difference of Co-Cr dental casting alloy are higher at the pH level of5.0than other pH groups, with significant difference (p<0.05) at37℃temperature. The mass difference has significance at different time point, and it is time-dependent. The liner change tendency of mass difference are different at different pH levels (p=0.000). There is a significant difference between pH level and temperature on the mass difference of Co-Cr dental casting alloy with significant difference (p>0.05).Conclusion(1) Artificial saliva has effect on the metal ions release of Co-Cr dental casting alloy.(2) The level of pH, temperature and time affect the metal ions release of Co-Cr dental casting alloy. Compared with the condition of PH=7and temperature=37℃, there are more release of Co-Cr dental casting alloy either PH>7or<7, and either lower or higher temperature. And there is a significant difference among them on the release of cobalt and chromium ions from Co-Cr dental casting alloy in artificial saliva. |
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