title: [The study of tarnish induced by Actinobacillus actinomycetemcomitans serotype b (Aay4) on titanium and Ti-75 alloys].
abstract: OBJECTIVE
  To study the tarnish induced by Aay4 on titanium and Ti-75 alloys.
  
  
  METHODS
  Pure titanium and Ti-75 alloys were machined into size of 10 mm x 10 mm x 1 mm in tablets(30 of pure titanium; 60 of Ti-75 alloys). Thirty specimens sampled randomly from Ti-75 alloy together with 30 specimens of titanium were subjected to chemical passivation treatment. 30 specimens of the pure titanium, depassivation Ti-75 alloy and passivation Ti-75 alloy were randomly divided into three groups (blank control group, media control group and inoculated media group) respectively, every group contains 10 specimens. Under the anaerobic conditions, the surfaces of the modified GAM media were inoculated with Aay4. The labeled specimens surfaces were then aseptically placed on top of the media surface for 10 weeks with one generation time per week. The specimens were removed after 10 weeks of incubation, immersed in 0.05% glutaradehyde solution to eliminate Aay4, rinsed with distilled water. After 2 weeks, the specimens were removed and observed visually or examined by MINOLTA CR-100 color apparatus.
  
  
  RESULTS
  Visual evaluation: Aay4 caused significant tarnish on specimens exposed to inoculated media, all the specimens surface changed into yellow color. Color apparatus evaluation: this result showed that comparing with the blank control, media control has no influence on all the specimens L*a*b* values (P > 0.05). Aay4 caused significant tarnish on specimens exposed to inoculated media, the result showed that there was significant difference between media control group and blank control group with inoculated media group on all the specimens L*a*b* values (P < 0.05).
  
  
  CONCLUSIONS
  Aay4 caused significant tarnish on pure titanium, depassivation Ti-75 alloys and passivation Ti-75 alloys by naked eyes and color apparatus, according CIE1976L*a*b* color system reading, the color of titanium and Ti-75 alloys changed from the yellow-green ranges to red-yellow ranges.
authors.affiliation: Department of Prosthodontics, College of Stomatology, Fourth Military Medical University, Xi'an 710032, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Song
authors.forename: J
authors.initials: J
authors.lastname: Xu
authors.forename: X
authors.initials: X
authors.lastname: Ma
mesh_terms: D016976:Aggregatibacter actinomycetemcomitans / Q000502:physiology*; D003116:Color; D003722:Dental Alloys / Q000737:chemistry*; D014025:Titanium / Q000737:chemistry*
chemical_list: D003722:Dental Alloys; D014025:Titanium