The Research Of Influence Produced By Nickel Ions On Streptococcus Mutans Biofilm

After teeth get missed, patients wearing denture is effect methods to restore some oral functions such as mastication, pronunciation, esthetic appearance. Nickel-chromium alloys are widely used in crowns and bridges for repairing damaged or lost teeth, for its favorable mechanical properties and low cost. Oral bacterial is in balance with oral tissue in the form of biofilm , in which it can make exchange of biochemistrical material and message with environment . However, when Ni²⁺ from nickel-chromium alloys is put into mouth as a variant substance, some changes in microecological conditions like caries or periodontitis may take place in mouth.This research aims to exam the influence produced by Ni²⁺ from nickel-chromium alloys on bacterium biofilm formed by streptococcus mutans. Through observing the changes in count of colony forming unit(CFU)and structure of biofilm by confocal laser scanning microscope(CLSM),It helps to discover the influence produced by Ni²⁺ on oral microecological conditions.The biofilm of Streptococcus mutans was prepared by allowing bacteria to grow on the surface of standard glass slide, which is cultivated in Ni²⁺ solution of different concentration. The adhesive microbial amount were determined by the colony forming unit counting method; Stained by Fluorescein C₂₀H₁₂O₅, a fluorescent stain, the biofilm structure was observed under the Confocal Laser Scanning Microscopy (CLSM). When the concentration of Ni²⁺ was above 7.5mg/L, the adhesive amount of streptococcus mutans began to decrease obviously. The higher the concentration of Ni²⁺ was, the smaller the adhesive amount, which was negative correlation.The structure of the biofilm was difference as the concentration of Ni²⁺ changed. When the concentration of Ni was 7.5mg/L, the adhesion between bacteria began to go down and the normal structure of biofilm disappeared gradually. When the concentration of nickel ions was above 30mg/L, the biofilm began to fall off and became thinner. When the concentration of nickel ions reached 120mg/L, no biofilm was formed.The result showed that When the concentration of nickel ions increased, the adhesive amount of streptococcus mutans decreased, so did the adhesion between bacteriae, and the formed single-bacteria-biofilm fell off with normal structure destroyed. However, it is necessary to do further research about whether there is cross-effect between the erosive alloy ions and the microbes, because of the antagonistic or cooperative action among microbes in the plaque.