Bacteria Adherence Properties of Nitrided Layer on Ti6Al4V by the Plasma Nitriding Technique

The nitrided layer on Ti6A14V substrate was prepared by the plasma nitriding technique. The sample was characterized by X-ray diffraction （XRD）, glow discharge optical emission spectroscopy （GDOES）, X-ray photoelectron spectroscopy （XPS）, and rough-meter. X- ray diffraction analysis reveals that TiN, Ti2N and Ti phase exist in the nitrided layer subsurface. GDOES analysis shows the thickness of the nitrided layer is about 3 ~tm. XPS analysis shows that there is higher N, lower A1 and lower V in the nitrided layer surface than in the Ti6A14V surface. Rough-meter analysis results show the roughness of the nitrided layer is greater than that of Ti6A14V alloy base. The bacteria adherence property of the nitrided layer on Ti6A14V substrate on the Streptococcus mutans was investigated and compared with that of Ti6A14V alloy by fluorescence microscope. It shows that the nitrided layer inhibits the bacteria adherence.

Bacteria Adherence Properties of Nitrogen-Doped TiO_2 Coatings by Plasma Surface Alloying Technique

In order to obtain a high-performance surface on 316L stainless steel （S. S） that can meet the requirements in medical material field environment, nitrogen-doped titanium dioxide （TiO2-xNx） was synthesized by oxidative annealing the resulted TiNx coatings in air. Titanium nitride coatings on 316L S. S were obtained by plasma surface alloying technique. The as-prepared coatings were characterized by X-ray diffraction, glow discharge optical emission spectrometer （GDOES）, scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. The bacteria adherence property of the TiO2-xNx coatings on S. S on the oral bacteria Streptococcus Mutans was investigated and compared with that of S. S by fluorescence microscopy. The mechanism of the bacteria adherence was discussed. The results show that the TiO2-xNx coatings are composed of anatase crystalline structure. SEM measurement indicates a rough surface morphology with three-dimensional homogenous protuberances after annealing treatment. Because of the photocatalysis and positive adhesion free energy, the TiO2-xNx coatings inhibit the bacteria adherence.

STUDY ON ADHERENCE ABILITY OF PERIODONTAL PATHOGENS AND CARIOGENIC BACTERIA TO HYDROXYAPATITE DISKS

Objective To study the adherence activity of six representative periodontopathic and cariogenic bacteria to hydroxyapatite disks. Methods Six periodontopathic and cariogenic bacteria of P. gingivalis, A. actinomycetemcomitans, F. nucleatum, S. sanguis, A. viscosus and S. mutans were cultured in modified MD-300 chemostat according to total fifteen experimental groups of single-specie and each pair of periodontal pathogens and cariogenic bacteria, respectively. After 1h attached live bacteria on removable hydroxyapatite disks was analyzed by culture technologies to evaluate the adherence level. Results The adherence activity of periodontopathic and cariogenic bacteria to HA was in the following order: S. sanguis > A. viscosus> S. mutans> A. actinomycetemcomitans > F. nucleatum > P. gingivalis. The number of periodontopathic bacteria to HA was enhanced by S. sanguis and A. viscosus,respectively.When mix-cultivated with S. mutans, the colonization of P. gingivalis was reduced significantly(P<0.001). Periodontopathic bacteria had no effect on the adherence activity of S. mutans and A. viscosus, except S. sanguis. Conclusion It was showed that the adherence activity of periodontal pathogens was weaker than that of cariogenic bacteria and emphasized the importance of bacterial adherence in determining the level of bacterial colonization on tooth surfaces. It was suggested that periodontopathic bacteria can utilize initial colonizers to become those predominant bacteria in periodontal ecosystem, which maybe have close relation to the periodontopathic mechanism.