A Study Of Surface Modification On NiTi Alloy Using Advanced Oxidization Method

Objective The aim of this study was to compare the quantity of Ni ion precipitation before and after NiTi alloy surface modification using advanced oxidization method, to analyse the influence of modification on adherence of streptococcus mutans and candida albicans.Methods To cast flake wax patterns(10mm×10mm×1mm) with casting wax. Selected specimens that strictly met the requirements.The first step was to polish the surface of specimens in mechanical ways.Then wiped the specimens with alcohol,cleaned the specimens with deionized water in the ultrasonic cleaner and reserved them after oven dryness.Surface modification of NiTi alloy was made by an advanced oxidization method.Saliva test was to immerse the polished groups and modified groups in artificial saliva (PH=6-7). Removed the test plates at the end of 1,2,3,4, 5 week(s) respectively, and detected the quantity of Ni ion precipitation using AA-240 atomic absorption spectrometer.Microbial adhesion test was to place the polished groups and modified groups of NiTi alloy in culture mediums which were contained with streptococcus mutans and candida albicans, at the end of 24hours,48hours and 72hours,the adhesive microbial amount in the culture mediums were determined by counting formation unit(CFU).Results In the saliva test, The quantity of Ni ion precipitation shows a rising trend both in the polished groups and the modified groups. Ni ion precipitation quantity of the modified groups is significantly less compared with that of the polished groups. In five weeks, the total quantity of Ni ion precipitation of modified groups is to be significantly less than that of the polished groups (P<0.01).In the microbial adhesion test,the adhesion level of streptococcus mutans and candida albicans were increased both in the polished groups and the modified groups. The adhesion level of streptococcus mutans and candida albicans in modified groups was significantly less than the level in the polished groups(P<0.01).Conclusions The results of saliva test and microbial adhesion test showed that advanced oxidization modification could significantly inhibit the Ni ion precipitation quantity and the adhesion ability of streptococcus mutans and candida albicans of NiTi alloy,which illustrates the surface stability of NiTi alloy was much improved.