The Electrochemical Corrosion Of HBIC-Ti Implant And Commonly Used Dental Alloys

Objective: The purpose of this study was to evaluate the corrosion behavior of HBIC-Ti implant and Au-Pt alloy, Ni-Cr alloy, Co-Cr alloy,casting pure Ti in artificial saliva with different pH and fluoride contents.it was usefud for references and basis for selecting suprastructure in dental implantation dental alloys in the clinic.Methods:1 Preparation of alloys specimens: HBIC-Ti implant(Ti-HBIC) of commonly used dental alloys : Ni-Cr alloys (N), Co-Cr alloy(C), casting pure Ti(T) are selected.Each type of alloy was cast into 4 samples under the manufacture instruction ,all samples were shaped into a cylindrical form, in order to constitute the cap of a rotating disk electrode. With4mm diameter , 10mm high , cylinders were wedged into PTFE pipage with 3.5mm diameter,the exposed surfase of metal is 0.1275mm2. All the samples were ground and polished as follows: the specimens were subjected to waterproof abrasive paper on 220, 400, 600, 800 grit silicon carbide then immerse into artificial saliva for 24 h.2 The preparation of the artificial saliva : Four different artificial saliva: pH6.8(A), pH 4(B), pH6.8with0.1%F-(C) ,pH 4 with0.1%F-(D).3 In A, B, C, D artificial saliva at 37±0.5℃, the corrosion potential(E corr), corrosion current density (Iccor) and polarizaion curve of there usual dental the materials,which were Ni-Cr alloy, Co-Cr alloy, casting pure titanium and HBIC-Ti implant, were tested by the classic three electrodes system of electrochemical method.4 Surface analysis by SEM.Results:1 The corrosion potential (Ecorr) of different materials in the different artificial saliva.Tab-31.1 Ecorr of five different metals in the artificial saliva A were Au>C>N>T>T-HBIC, Ecorr Au was bigger than other four kind of metals(p<0.05), Ecorr N, Ecorr C were bigger than Ecorr T, Ecorr T-H(p<0.05),There were no signifcant difference between Ecorr N and Ecorr C, Ecorr T and EcorrT-H, (p>0.05).1.2 Ecorr of Tgroup and T-Hgroup in the artificial saliva A,B,C,D were EcorrA 0.05).2.2 Nickel-chromium alloy The corrosion current density of Ni-Cr alloy tesed by A, B, C, D artificial saliva respectively were The corrosion current density tested in artificial saliva B and D exceed tested in artificial saliva A and C, there is significant diffreence (p<0.05),but there is no significant diffreence in the corrosion current density tested in artificial saliva between C and D, and Iccor tested in artificial saliva between Aand B(P>0.05).2.3 Cobalt-chromium alloy The corrosion current density of Co-Cr alloy tesed by A, B, C, D artificial saliva respectively wereCC0.05).2.4 Casting pure titanium The corrosion current density of Casting pure Ti tesed by A, B, C, D artificial saliva respectively were TA< TC0.05).2.5 HBIC-Ti implant The corrosion current density of HBIC -Ti tesed by A, B, C, D artificial saliva respectively were T-HA< T-HB0.05).3 The corrosion current density of different materials in the same artificial saliva (IccorμA /cm2)3.1 In the artificial saliva A the corrosion current density of five metals respectively were N>C> T> T-H>Au, The corrosion current density tested of Au group and T group, T-H group was smaller than that N group and C group , there was significant difference (p<0.05). but there was no significant difference in the corrosion current density between N group and C group, among Au group ,T group and T-H group (P>0.05). In the artificial saliva B the corrosion current density of five metals respectively were N>C>Au>T>T-H, The corrosion current density tested of T group, T-H group was smaller than that of Au group, N group and C group, Au group was smaller than that of N group and C group ,there were significant difference (p<0.05). but there was no significant difference in the corrosion current density between N group and C group, T group ,and T-H group (P>0.05). 3.2 In the artificial saliva C, The corrosion current density tested of five kind of metals were no significant difference(p>0.05), In the artificial saliva D, the corrosion current density was AuD group0.05).4 Surface analysis by SEM:4.1 Au-Pt alloy: No obvious corrosion was observed on the surface of Au-Pt alloy tested in artificial saliva A and C, but in artificial saliva B and D there was some small sporadic shallow corrosion spot.4.2 Ni-Cr alloy: there was obvious corrosion of Ni-Cr alloy tested in artificial saliva A and C, It was typical pitting appeara- -nce,and pH degrade intensified the alloy corrosion.4.3 Co-Cr alloy: Exfoliatus destroy was observed on the surface of Co-Cr alloy tested in four different artificial saliva , and pH degrade intensified the alloy corrosion.4.4 Casting pure Ti and Ti-HBIC implant: There were both no obvious corrosion on the surface of two type of Ti tested in art -ificial saliva A,Band C, but in the artificial saliva D honeyc -omb appearance was observed in high power, the inhere appearance of metal was destroyed completely. Conclusion:1 In the neutral artificial saliva, the corrosion current density of Ni-Cr alloys, Co-Cr alloy, casting pure Ti, HBIC-Ti implant all smaller than 10-6, five kind of materials had a good corrosion resistance, but Au-Pt alloy and pure Ti presented the better corrosion resistance, and were far superior to that of Ni-Cr alloy and Co-Cr alloy.2 The corrosion current density of Ni-Cr alloys and Au-Pt alloy increased significantly, but Co-Cr alloy, casting pure Ti, HBIC-Ti implant was free of influnce.3 Adsition of F- in the acidic artificial saliva promoted the corrosion current density of five metals, casting pure Ti, HBIC-Ti implant were more sensitive than other alloys.there was a signifcant difference with that in pH=6.8 artificial saliva.4 Decreacing of pH and adsition of F- in the acidic artificial saliva intensified the electrochemical corrosion of implant and crown material, so removal bacterial plaque to maintain pH at normal limits and adjusting fluorine praeparatum to alkalinity or neutrality would be good to decreace the electrochemical corrosion.