title: Effective single-charge end point of cordless light-emitting diode light-curing units.
abstract: BACKGROUND
  The purpose of this study was to evaluate the battery lives of cordless light-emitting diodes (LEDs) and their effect on orthodontic bracket bond strength.
  
  
  METHODS
  One hundred eighty-six metal orthodontic brackets were bonded to extracted molars. Two LED light-curing units (L. E. Demetron [SDS/Kerr, Orange, Calif] and Ortholux [3M Unitek, Monrovia, Calif]) were evaluated. Each light was used to bond 93 specimens. One bracket was bonded every 5 minutes until the battery ran out. The lights were activated for 20 seconds, then automatically turned off for 40 seconds every minute (33% duty cycle) without recharging. Bonded specimens were stored in water at 37 degrees C for 24 hours and then subjected to shear force with a universal testing machine until bracket failure.
  
  
  RESULTS
  Repeated measures ANOVA detected significantly weaker mean shear bond strength and fewer consecutive cures with the Ortholux compared with the L. E. Demetron light-curing unit. However, when the first 5 time points were excluded, there were no differences between the 2 lights, demonstrating that the lights performed similarly after the first 20 minutes of operation Just before battery failure, both lights still provided the same power density as at the beginning.
  
  
  CONCLUSIONS
  Both light-curing units provided adequate power density for up to 2 hours without recharging at a 33% duty cycle. There was no significant decrease in power in cordless LED light-curing units as the battery life approached its end point.
authors.affiliation: Department of Orthodontics, Travis Air Force Base, Fairfield, Calif, USA.
authors.forename: Robert H
authors.initials: RH
authors.lastname: Judy
authors.forename: William J
authors.initials: WJ
authors.lastname: Dunn
authors.forename: Arpita B
authors.initials: AB
authors.lastname: Patel
authors.forename: Timothy
authors.initials: T
authors.lastname: Swanson
mesh_terms: D000704:Analysis of Variance; D017438:Bisphenol A-Glycidyl Methacrylate / Q000528:radiation effects; D001840:Dental Bonding; D003748:Dental Equipment; D003799:Dental Stress Analysis; D011211:Electric Power Supplies; D006801:Humans; D008027:Light; D008963:Molar; D016910:Orthodontic Brackets; D044367:Phase Transition; D019279:Resin Cements / Q000528:radiation effects*; D012666:Semiconductors; D033081:Shear Strength
chemical_list: D019279:Resin Cements; C065742:Transbond; D017438:Bisphenol A-Glycidyl Methacrylate