[Study on the surface roughness of three dental alloys soaked in artificial saliva]

The aim of this study was to investigate the corrosion behavior of three metal materials for dental use (Co-Cr alloy, Ni-Cr alloy, titanium) by measurement of their surface roughness after soaked in artificial saliva with two different pH values.

Standard samples were casted respectively from 3 different alloys and grided into the same roughness .Then the samples were exposed to artificial saliva with two different pH values. After three months,the surface roughness of the samples was tested, and the microstructure of surfaces was studied by metalloscope. The data were analyzed with SPSS11.0 software package for one-way ANOVA and t test.

There was significant difference in surface roughness of three alloys after exposed to artificial saliva with pH5.6. The surface roughness values of three alloys were listed as follows: Ni-Cr alloy>Co-Cr alloy >titanium(P<0.01). When exposed to artificial saliva with pH7.0, Ni-Cr alloy was found rougher than Co-Cr alloy and titanium(P<0.01), while there was no significant difference in roughness between Co-Cr alloy and titanium(P>0.05).Ni-Cr alloy and Co-Cr alloy soaked in artificial saliva with pH5.6 were found rougher than the same material in artificial saliva with pH7.0(P<0.01).The microstructure of the samples' surface verified the results.

Titanium was stable not only in neutral environment but also in acid environment. The corrosion resistance of Co-Cr alloy and Ni-Cr alloy was superior in neutral environment than in acid environment. The corrosion resistance of the three alloys was: Titanium >Co-Cr alloy >Ni-Cr alloy.