title: Effect of shorter polymerization times when using the latest generation of light-emitting diodes.
abstract: BACKGROUND
  Recent studies have suggested that a 10-second cure time with a high-energy quartz-tungsten-halogen (QTH) or a light-emitting diode (LED) light might be adequate when bonding orthodontic brackets to tooth enamel. The purpose of this study was to evaluate the ability of the latest generation of QTH and LED light-curing units (LCUs) to bond orthodontic brackets to teeth at decreased polymerization times.
  
  
  METHODS
  Two LED LCUs (Ortholux LED, 3M Unitek, Monrovia, Calif; UltraLume LED 5, Ultradent Products, South Jordan, Utah) and a QTH LCU (Optilux 501, Demetron, Danbury, Conn) were evaluated. One hundred eighty metal orthodontic brackets were bonded to extracted human molars. The specimens were divided into 9 groups (3 lights and 3 curing times) of 20 teeth each. Each group was cured with 1 of the 3 lights for 20, 10, or 6 seconds. Thirty minutes after polymerization, the specimens were subjected to shear force on a universal testing machine until bracket failure.
  
  
  RESULTS
  Two-way ANOVA detected significant differences among the main effects of light type and cure time. Tukey post-hoc tests determined that brackets bonded by all light types had lower bond strengths with the 6-second cure than the 20-second cure (P < .001). The highest bond strengths were obtained with the Optilux 501 QTH LCU and the UltraLume LED 5 LCU at the longest cure time of 20 seconds.
  
  
  CONCLUSIONS
  It is recommended that orthodontic brackets be photopolymerized for at least 20 seconds with the QTH or the LED LCU before the archwires are engaged.
authors.affiliation: Tri-Service Orthodontic Residency Program, Lackland Air Force Base, San Antonio, TX, USA.
authors.forename: Y Teresa
authors.initials: YT
authors.lastname: Silta
authors.forename: William J
authors.initials: WJ
authors.lastname: Dunn
authors.forename: Charles B
authors.initials: CB
authors.lastname: Peters
mesh_terms: D000704:Analysis of Variance; D017438:Bisphenol A-Glycidyl Methacrylate / Q000528:radiation effects; D001840:Dental Bonding; D003748:Dental Equipment; D003799:Dental Stress Analysis; D006219:Halogens; D006801:Humans; D008027:Light; D008422:Materials Testing; D008963:Molar; D016910:Orthodontic Brackets; D044367:Phase Transition; D019279:Resin Cements / Q000528:radiation effects*; D012666:Semiconductors; D033081:Shear Strength; D013997:Time Factors
chemical_list: D006219:Halogens; D019279:Resin Cements; C065742:Transbond; D017438:Bisphenol A-Glycidyl Methacrylate