title: Light-emitting diode vs halogen light curing of orthodontic brackets: a 15-month clinical study of bond failures.
abstract: BACKGROUND
  Previous in-vitro investigations reported no significant differences in the bond strength of brackets cured with conventional halogen lamps and those cured with light-emitting diodes (LED), even though LED curing times are much shorter. However, it is not known how LED curing performs in the oral cavity. The purpose of this randomized clinical trial was to evaluate the clinical performance of brackets cured with 2 light-curing units: a conventional halogen unit and an LED.
  
  
  METHODS
  Thirty patients treated with fixed appliances were included in this study. The bonding followed a contralateral quadrant pattern: in each patient, 2 quadrants were cured with the conventional halogen unit, and the other 2 quadrants were cured with the LED unit. The study had a single blind controlled design with a within-patient comparison of the 2 curing techniques, and the patients were allocated randomly. A total of 544 stainless steel brackets were examined for bracket failure. Location (tooth), cause, and date of failure were recorded over 15 months. Statistical analyses were performed with the Kaplan-Meier survival estimates and the log rank test.
  
  
  RESULTS
  No statistically significant differences were found in total bond failure rate or in mean survival time between brackets cured with the halogen light and those cured with the LED. Neither were significant differences found between the 2 lights when the clinical performances of the maxillary and mandibular arches were compared, or when the posterior and anterior segments were compared.
  
  
  CONCLUSIONS
  These results show that curing with an LED does not result in more bond failures or shorter time to failure when compared with conventional halogen light curing. Curing with an LED is an acceptable alternative to conventional halogen light curing.
authors.affiliation: Department of Orthodontics and Dentofacial Orthopaedics, Ragas Dental College and Hospital, Chennai, India. ennar@md3.vsnl.net.in
authors.forename: N Rengarajan
authors.initials: NR
authors.lastname: Krishnaswamy
authors.forename: Chakravarthi
authors.initials: C
authors.lastname: Sunitha
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D003722:Dental Alloys; D001840:Dental Bonding / Q000295:instrumentation*; D003748:Dental Equipment; D003799:Dental Stress Analysis; D004868:Equipment Failure; D005260:Female; D006219:Halogens; D006801:Humans; D053208:Kaplan-Meier Estimate; D008027:Light; D008297:Male; D016910:Orthodontic Brackets; D044367:Phase Transition; D019279:Resin Cements / Q000528:radiation effects*; D012666:Semiconductors; D016037:Single-Blind Method; D013193:Stainless Steel
chemical_list: D003722:Dental Alloys; D006219:Halogens; D019279:Resin Cements; C477790:Transbond XT; D013193:Stainless Steel