Corrosion and discoloration of metallic biomaterials such as titanium are the major concern when applied for the dental implants and the bases of prostheses. This study aimed to investigate the biocorrosion behavior of titanium under artificial biofilm.
Methods:
Streptococcus mutans NCTC10449 were grown in the 0.5%-glucose-containing complex medium (designated as viable cells (VC)). Part of the cells was treated with autoclaving (designated as killed cells (KC)). Samples of commercially-pure titanium (CPTi) ASTM Grade II (1×10×10 mm) were ground up to the one side mirror polishing. Experimental apparatus with a well (4.0 mm in diameter and 2.0 mm deep) was made of polymethyl methacrylate with a CPTi at the bottom. VC or KC were packed into the well as artificial biofilm and kept at 37°C for 90 min. Before and after biofilm formation for 90 min, corrosion current on the surface of CPTi was measured using computer-controlled potentiostat (VersaSTAT4, TOYO Corporation, Tokyo, Japan). The amount of titanium eluted from CPTi surface into VC or KC was measured by inductively coupled plasma mass spectrometry (ICP-MS; HP4500, Agilent, Tokyo, Japan).
Results:
In the presence of VC biofilm, corrosion current of CPTi surface was significantly increased (1.37±0.79 to 41.27±12.57 nA, p<0.01), while in the presence of KC biofilm, there was no significant difference (0.20±0.21 to 2.67±2.78 nA, p=0.30). No significant elution of titanium was detected in the presence of VC or KC biofilm.
Conclusions:
The results of this study revealed that presence of VC for short time caused electrochemical change on the titanium surface, suggesting that biofilms on the surface of titanium could corrode titanium, although it seems to be not enough to elute titanium from the surface. This method could make it possible to evaluate the biocorrosion behavior of several metallic biomaterials under biofilm. Supported by MEXT, Japan.