title: Microleakage beneath ceramic and metal brackets photopolymerized with LED or conventional light curing units.
abstract: OBJECTIVE
  To test the null hypotheses that (1) the type of light curing unit used (quartz-tungsten-halogen [QTH] or light-emitting diode [LED]) would not affect the amount of microleakage observed beneath brackets, and (2) the bracket type used (ceramic or metal) would not influence the amount of microleakage observed beneath brackets.
  
  
  METHODS
  40 freshly-extracted human premolars were randomly assigned into 4 bonding groups (n = 10/group): group 1, metal bracket + LED-cured Transbond XT; group 2, ceramic bracket + LED-cured Transbond XT; group 3, metal bracket + QTH-cured Transbond XT; and group 4, ceramic bracket + QTH-cured Transbond XT. The teeth were kept in distilled water for 1 month, and thereafter subjected to 500 thermal cycles. Then, specimens were sealed with nail varnish, stained with 0.5% basic fuchsin for 24 hours, sectioned, and photographed under a stereomicroscope. Microleakage was scored with regard to the adhesive-tooth interface and the bracket-adhesive interface at both incisal and gingival margins. Statistical analysis was accomplished by Kruskal-Wallis and Mann-Whitney U-tests with Bonferroni correction.
  
  
  RESULTS
  Microleakage was observed in all groups. When an LED curing unit was used for adhesive polymerization, ceramic brackets displayed significantly less microleakage than metal brackets in both tooth-adhesive and bracket-adhesive interfaces. When a QTH curing unit was used, ceramic brackets displayed significantly less microleakage than metal brackets in the bracket-adhesive interface in both gingival and incisal margins.
  
  
  CONCLUSIONS
  Ceramic brackets cured with LED units were the best combination, demonstrating the lowest microleakage scores.
authors.affiliation: Osmanli Dis Hastanesi, Conservative Dentistry, Ankara, Turkey.
authors.forename: Serdar
authors.initials: S
authors.lastname: Arikan
authors.forename: Neslihan
authors.initials: N
authors.lastname: Arhun
authors.forename: Ayça
authors.initials: A
authors.lastname: Arman
authors.forename: Sevi Burcak
authors.initials: SB
authors.lastname: Cehreli
mesh_terms: D001641:Bicuspid; D002516:Ceramics; D001840:Dental Bonding / Q000379:methods; D003748:Dental Equipment; D003763:Dental Leakage / Q000209:etiology / Q000517:prevention & control*; D006219:Halogens; D006801:Humans; D008027:Light; D008422:Materials Testing; D008670:Metals; D016382:Orthodontic Appliance Design; D016910:Orthodontic Brackets / Q000009:adverse effects*; D044367:Phase Transition; D019279:Resin Cements / Q000528:radiation effects*; D012666:Semiconductors; D018709:Statistics, Nonparametric; D013674:Technology, Dental / Q000379:methods*
chemical_list: D006219:Halogens; D008670:Metals; D019279:Resin Cements; C477790:Transbond XT