| Objective: Concertration of nickel ion releasing from dental Ni-Cr alloy with or without nano-amorphous diamond film were measured and recorded in several immersion steps: neutrally artificial Saliva for 3 days, 7days; Then 2 hours treating in two kind of artificial Saliva (PH6.8, PH4); At last in neutrally artificial Saliva for 7days. Data obtained by Atomic Absorption Spectrophotometer in all experimental groups were analyzed by statistical package for the social science 16.0. The results were discussed and provide test data for Ni-Cr modification.Methods: 1 Preparation of alloy specimens: Ni-Cr alloy which was used as dental restoration materials were selected, the alloy constituents were listed in Table. The finished Ni-Cr alloy cylinder with diameter of 0.9mm was cut into 36 specimens, 5mm×5mm×25mm for each one in size. Each specimen with no visible deformation and trachoma was polished by the standard of dental Ni-Cr alloy, and then be cleared by alcohol sponge, washed by soapy water and steamed. Eighteen specimens were randomly selected as experimental group, the other eighteen specimens as control group. In experimental group, specimens were plated with nano-amorphous diamond film (thickness as 50nm) by CVD method. 2 Immersion service: Two different kinds of immersion solution were used in this study: B(pH6.8), and C( pH4). The experimental group were further divided into three text groups randomly: Sa, Sb ,Sc(n=6 in each group); the control group were also divided randomly into three groups: Da Db Dc(n=6); Different groups should experienced such steps as following: Sa and Da in BS for 3 days; Sb and Db in B for 1 week first, then changed into new B for 2 hours respectively, after that moved to new B again for another 7days; Sc and Dc in B for 1 week, then in C respectively for two hours, at last also be immersed in B for 7 days. Whenever each step ended during experiment, the solution should be collected immediately, in which nickel ion should be measured by special instrument. 3 Detection of nickel ion releasing: Nickel ion which released into the immersed solutions was measured with Atomic Absorption Spectroscopy (AAS), and results were analyzed statistically.Results: 1 Amount of Nickel ion release in experiment group:There was no significant difference in nickel ion release between Sa and Sb(first step) (P>0.05), as well as no difference between Sb and SC(second step),(P>0.05), and no difference between Sb and Sc (third step)(P>0.05). 2 Amount of Nickel ion release in control group: There was no significant difference in nickel ion release between Da Db(first step), but showed difference between Db and Dc (second step) (P<0.05), and no significant difference between Db and Dc(third step) (P>0.05). 3 Comparison between experimental group and control group: There were significant difference between Sa and Da, Sb and Db(first step), showed that whether plating or not had no interaction with time (P>0.05); but had significant difference among Sb and Db(second step), Sc and Dc(second step), indicated that there was interaction between PH and plated treatment(P<0.05). There was no significant difference in nickel ion release between plated groups Sc and Dc(third step)(P>0.05).Conclusions: 1 Nickel ion releasing from Ni-Cr alloy could happened in pH 6.8 artificial saliva, the amount of Nickel ion decreased while time passed; nano-amorphous diamond film could effectively decrease Nickel ion releasing in its primary immersion. 2 Decrease of pH could increase the amount of Nickel ion releasing. So nano-amorphous diamond film can prevent the corrosion of dental Ni-Cr alloy, protect alloy effectively and reduce Nickel ion release. 3 With pH value of Artificial saliva turning from Acidity into neutrality, amount of precipitation of nickel-chromium alloy nickel ions decreases. the amount of precipitation of plated nickel-chromium alloy nickel ions has no significant change and lower than that of unplated one.
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