The Effect Of Fluoride Concentration On The Corrosion Behavior Of Cobalt-chromium Alloy Fabricated By Two Different Technology

Objective：To investigate the effect of fluoride concentration on the corrosion behavior ofcobalt-chromium alloy fabricated by two different production in a simulated oralenvironment.Methods：Specimens for SLM group and cast group which were fabricated with the same(Co-Cr)alloy were manufactured as cylinders (12mm diameter and3mm thickness).The metal specimens were divided into2groups after the same surface pretreatment.The corrosion behavior of the first group specimens was studied using potentiod-ynamic polarization test under different NaF concentration (0%、0.05%、0.2%)contaning oral environment, In the other group metal specimens surface roughnesswere measured after immersed for3weeks and then their surface morphology wasobserved by field emission scanning electron．The experimental results were analyzedStatistically.Results：1. Electrochemical corrosion test:1) The corrosion potential (Ecorr) value of cast cobalt-chromium alloy decreasedwith the increasing of NaF concentration in acidic artificial saliva. The corrosionpotential (Ecorr), corrosion current density (Icorr) and polarization resistance (Rp)values of cobalt-chromium alloy of fabricated by two different production changedsignificantly when NaF concentration was0.2%.2) There were significant differences for cast cobalt－chromium alloy electricPotential of corrosion at the fluoride concentration of0%and0.05%(P<0.05), Ecorr,Icorrand Rpvalues at the fluoride concentration of0%and0.2%(P<0.05). Others hadno significant difference(P>0.05). 3) There were significant differences for SLM group cobalt－chromium alloyEcorrand Icorrvalues at the fluoride concentration of0%and0.2%(P<0.05). Othershad no significant difference(P>0.05).4) There were significant differences for SLM group and cast group cobalt－chromium alloy electric Potential of corrosion at the fluoride concentration of0.05%(P<0.05).The corrosion potential, corrosion current density and polarizationresistance values of cobalt-chromium alloy of fabricated by two different productionchanged significantly when NaF concentration was0.2%(P<0.05). Others had nosignificant difference(P>0.05).2. Immersion corrosion test：1) Cast cobalt-chromium alloy surface roughness was increased with theincreasing of NaF concentration in acidic artificial saliva.There was significantdifference in surface roughness of SLM group and cast group cobalt-chromium alloyafter immersion at high concentration fluoride artificial saliva.2) SLM group and cast group cobalt-chromium alloy surface roughness have onStatistically significant difference at before immersion（P＞0.05）. After immersiontest between the SLM group and cast group cobalt-chromium alloy, at the fluorideconcentration of0.05%and0.2%, the surface roughness between SLM group andcast group had Statistically significant differenc（eP＜0.05）. Others had no significantdifference(P>0.05).3) The surface roughness of cast cobalt-chromium alloy had statisticallysignificant differences between before and after immersion（P＜0.05）at the fluorideconcentration of0.05%, SLM group cobalt－chromium alloy had no statisticallysignificant difference（P＞0.05）. The differences of the two groups before and afterimmersion were statistically significant difference （P＜0.05） at the fluorideconcentration of0.2%.4) The surface roughness of the SLM group cobalt－chromium alloy2.0%NaFgroup and0%NaF group,2.0%NaF group and0.05%NaF group had statisticaldifference after immersion in acidic artificial saliva（P＜0.05）.The surface roughnessof the cast group cobalt-chromium alloy2.0%NaF group and0%NaF group,2.0%NaF group and0.05%NaF group,0%NaF group and0.05%NaF group had statistical difference after immersion in acidic artificial saliva（P＜0.05）．Others hadno significant difference(P>0.05).Conclusions:1) The Presence of fluorides influence the corrosion resistance of SLM groupand Cast group cobalt-chromium alloy.2) The sensitivity to fluoride of two group cobalt-chromium alloys is Castcobalt-chromium alloy＞SLM group cobalt－chromium alloys.3) Patients with prostheses of these two production cobalt-chromium alloy arenot advised to use high concentration fluoride products long.