title: [The ultrastructure and activities of free radical scavenger in discolored gingiva adjacent to porcelain fused to metal crowns].
abstract: OBJECTIVE
  This study was designed to study the discolored gingiva adjacent to porcelain fused to metal (PFM) crowns in terms of ultrastructure , SOD and GSH activities in 40 cases.
  
  
  METHODS
  The discolored gingival ultrastructures were observed and metal X-ray energy level was analyzed;The activities of SOD and GSH were measured and compared with normal control by student's t test and one-way ANOVA with SPSS10.0 software package.
  
  
  RESULTS
  The discolored gingival ultrastructure had changes compared with the normal gingiva. Nickel and chromium were not found in the particles through X-ray energy machine within the discolored gingiva adjacent to PFM crown. The activities of SOD and GSH in discolored gingiva were significantly different from control(P<0.05) and the values at 6 to 18 months were significantly different from those at other times.
  
  
  CONCLUSIONS
  The ultrastructure underwent changes in discolored gingiva after PFM restoration; the activity of SOD and GSH in discolored gingiva changed to result in apoptosis, and discoloration.
authors.affiliation: Department of Prosthodontics, School of Stomatology, China Medical University, Shenyang 110002, Liaoning Province, China. zhangzhongti@163.com
authors.forename: Zhong-ti
authors.initials: ZT
authors.lastname: Zhang
authors.forename: Lu
authors.initials: L
authors.lastname: Yan
authors.forename: Ming
authors.initials: M
authors.lastname: Zhong
authors.forename: Xiao-dong
authors.initials: XD
authors.lastname: Yang
authors.forename: Hong-jun
authors.initials: HJ
authors.lastname: Ai
mesh_terms: D003116:Color; D003442:Crowns; D003776:Dental Porcelain; D016166:Free Radical Scavengers; D005881:Gingiva / Q000378:metabolism*; D006801:Humans; D009532:Nickel
chemical_list: D016166:Free Radical Scavengers; D003776:Dental Porcelain; D009532:Nickel