In Vitro Study On Surface Properties Of Cobalt Chromium Alloy Fabricated By Two Different Methods

In teams of physical properties and mechanical properties, selective laserforming cobalt chromium alloy are conformed better than the cobalt chromiumalloy,casted by traditional casting process. But in the oral environment,oral bacterialwill adhere to the surface of the cobalt chromium alloy, even cause some oraldiseases.Objective:To evaluate the differences of the surface free energy and Streptococcus mutans’adhesion between different materials，including selective laser forming cobaltchromium alloy、Wirobond280cobalt chromium alloy and SG cobalt chromiumalloy,in a simulated oral environment. Then to provide some experimental data fordoctors and offer options for the prevention of their occurrence.Materials and methods:Materials: three groups made of different Co-Cr alloy with the same size andshape:1) A group-SG cobalt chromium alloy specimen: Co63.9%Cr24.7%Mo5%W5.4%Si1%(BEGO company, Wirocast S, Germany).2) B group-Wirobond280cobalt chromium alloy specimen:Co60.2%Cr25%Mo4.8%W6.2%(Ga2.9%)BEGO, Wirocast S,Germany).3) C group-selective laser forming cobalt chromiumalloy specimen:Co60.5%Cr28%Mo5%W9%Si1.5%(BEGO company, WirocastS,Germany). Methods: The specimen were polished step by step by SiC sandpaperrespectively until ABC have the same surface roughness (Ra)(0.32-0.33um), thenuse the environmental scanning microscopy test the ABC’s surface morphology anduse the optical contact angle measuring instrument (KRUSS DSA100) to obtain theirsurface contact angle; Put ABC into sterile artificial saliva (PH6.8）respectively for24hours.After24hours,put the samples into the fluid MRS culture mediumcontaining Ua159for48hours and finally the adhesive microbial amount andmicrobial amount in the culture medium were determined by counting the clonalformation unit. Result:：（1）By single factor analysis of variance, the test result of ABC’s surfacecontact angle showed that: three is no significant difference ibetween them(P>0.05).（2）In the same culture situation, the number of Streptococcus mutans adherenton there surfaces have no statistical difference (P>0.05).Conclusion:（1）In the same culture condition, the surface free energy of laser formingcobalt chromium alloy is similar to others.（2）Under the same condition, the number of Streptococcus mutans adherenton laser forming cobalt chromium alloy is similar to the other two groups.The laserforming cobalt chromium alloy can be used safely in clinic.