title: [Study of factors affecting tooth discoloration during fixed orthodontics in vitro].
abstract: OBJECTIVE
  To investigate effects of acid etching, adhesives, brackets and debonding process on tooth color during direct bonding technique.
  
  
  METHODS
  One hundred freshly extracted premolars were divided into blank control, acid etching, adhesive, acid etching+adhesive and acid etching+adhesive+bracket group. Computerized colorimeter was utilized to evaluate L*, a* and b* of tooth color parameters before treatment, 7 days and 30 days after treatment. SPSS 16.0 software package was utilized for statistical analysis.
  
  
  RESULTS
  At 7 day, ΔE** value in all experimental groups were significantly higher than blank control group. ΔE* values of acid etching+adhesive+bracket group, and acid etching group were greater than 3.3, showing that recognizable clinic change was observed, but no significant difference was observed between the 2 groups. At 30 d, for ΔE* value, acid etching+adhesive+bracket group > acid etching group, and acid etching+adhesive group > adhesive group > blank control group. Recognizable clinic change was observed in all experimental groups (ΔE*>3.3).
  
  
  CONCLUSIONS
  In fixed orthodontic procedures, acid etching and metal erosion resulting from long time wearing braces are two important factors leading to enamel discoloration, and adhesives removing procedures may also affect tooth discoloration.
authors.affiliation: Department of Orthodontics, School and Hospital of Stomatology, Fujian Medical University. Fuzhou 350002, Fujian Province, China.E-mail:xlyyydentist@163.com.
authors.forename: Lin-yu
authors.initials: LY
authors.lastname: Xu
authors.forename: Min
authors.initials: M
authors.lastname: Dong
authors.forename: You-guang
authors.initials: YG
authors.lastname: Lu
authors.forename: Lang
authors.initials: L
authors.lastname: Lei
mesh_terms: D000269:Adhesives; D001641:Bicuspid; D001840:Dental Bonding; D017005:Dental Debonding; D003743:Dental Enamel; D016910:Orthodontic Brackets; D009970:Orthodontics; D019279:Resin Cements; D014075:Tooth Discoloration
chemical_list: D000269:Adhesives; D019279:Resin Cements