Effect Of Cobalt-Chromium Alloy And Titanium Surface Polishing Methods On Wettability And Bacterium Adhesion

ObjectTo study the influence of mechanical polishing,electro-polishing,chemical polishing and combined polishing methods on the wettability and bacteria adhesion of cobalt-chromium alloy and pure titanium.Investigate the best polishing method for each material.MethodsThe casting of titanium and cobalt-chromium alloy were respectively processed into the size of 15mm* 8mm* 1.2mm in tablets.Each material was prepared for 36 specimens,randomly divided into 6 groups, dealt with 6 treatments. Surface roughness were measured by topographer and the advacing contact angleθα,reducing contact angleθγof the two materials in artificial saliva were tested,calculate contact angle hysteresisΦ=θα-θγto reflect the specimens'wettability.International standard ingbritt,serotype c,streptococcus mutans was carried out in the bacterial adhesion experiments and colony counting method was used.One-way ANOVA was performed with SPSS 16.0 software package,the reslut was carried out by LSD-t test.Result1) The surface roughness of cobalt-chromium alloy dealt with mechanical polishling only was 0.308±0.027μm,electrolytic polishing combined with coarse grinding was 0.568±0.030μm,electrolytic polishing after fine grinding was0.1517± 0.018μm.They were both able to meet the clinical standard:surface roughness <0.6μm.The combined polishing was the most effective method,which could reduce the roughness value to 0.093±0.014μm.2) The surface roughness of titanium specimens by mechanical polishling is 0.782±0.025μm,which could not meet the clinical standard,by chemical polishing after coarse grinding the roughness value was 0.562±0.037μm,chemical polishing combined with fine grinding was 0.277±0.016μm,joint polishing could achieve the best results,by which the surface roughness was 0.130±0.012μm,they were able to reach the clinical standard.3) Contact angle hysteresis of cobalt-chromium alloy and titanium specimens decreased with the surface roughness decreased, which cause wettability reduced.4) Bacterial adhesion experiment's results showed that with the polishing process increased,surfaces bacterial adhesion of cobalt chromium alloy and titanium specimens decreased.For cobalt-chromium alloy mechanical combined with electro-polishing had the best effect, and for titanium mechanical,chemical combined polishing had the least amount of adhesion plaque.Conclusion1) Cobalt-chromium alloy with enough grinding, mechanical polishing or electrolytic polishing achieve good polishing effect.As for titanium specimens chemical polishing is better than mechanical polishing, combined polishing for the two materials can best minimize surface roughness.2) Cobalt-chromium alloy and titanium in artificial saliva contact angle hysteresis decrease with the reduction of surface roughness.The lower down of wettability can enhance the material's antibacterial properties.3) Bacterial adhesion on the specimen is associated with surface roughness, reducing surface roughness can reduce the adhesion of bacteria on the specimens surface.Polishing can effectively decrease surface roughness,inhibit bacterial adhesion.