title: Light energy attenuation through orthodontic ceramic brackets at different irradiation times.
abstract: OBJECTIVE
  To evaluate the total light energy (TLE) transmission through three types of ceramic brackets with, bracket alone and with the addition of orthodontic adhesive, at different exposure durations, and to compare the microhardness of the cured adhesive.
  
  
  METHODS
  Three different makes of ceramic brackets, Pure Sapphire(M), Clarity™ ADVANCED(P) and Dual Ceramic(P) were used. Eighteen specimens of each make were prepared and allocated to three groups (n = 6). MARC(®)-resin calibrator was used to determine the light curing unit (LCU) tip irradiance (mW/cm(2)) and TLE (J/cm(2)) transmitted through the ceramic brackets, and through ceramic bracket plus Transbond™ XT Light Cure Adhesive, for 5, 10 and 20 s. Vickers-hardness values at the bottom of the cured adhesive were determined. Statistical analysis used one-way analysis of variance (ANOVA); P = 0.05.
  
  
  RESULTS
  TLE transmission rose significantly among all samples with increasing exposure durations. TLE reaching the adhesive- enamel interface was less than 10 J/cm(2), and through monocrystalline and polycrystalline ceramic brackets was significantly different (P < 0.05). Pure Sapphire(M) showed the highest amount of TLE transmission and Vickers-hardness values for 5, 10 and 20 s.
  
  
  CONCLUSIONS
  Following manufacturer's recommendations, insufficient TLE may be delivered to the adhesive: increasing the exposure durations may be required when adhesive is cured through ceramic brackets. Clinicians are advised to measure the tip irradiance of their LCUs and increase curing time beyond 5 s. Orthodontic clinicians should understand the type of light curing device and the orthodontic adhesive used in their practice.
authors.affiliation: a The University of Medicine and Pharmacy , Tg-Mures , Romania.|b The University of Edinburgh , Edinburgh , Scotland , UK.
authors.forename: Ario
authors.initials: A
authors.lastname: Santini
authors.affiliation: c Department of Orthodontics , Edinburgh Dental Institute.|d Orthodontic Unit, Bukit Minyak Dental Clinic , Penang , Malaysia.
authors.forename: Szu Hui
authors.initials: SH
authors.lastname: Tiu
authors.affiliation: e Department of Orthodontics , Edinburgh Dental Institute, University of Edinburgh , Scotland , UK.
authors.forename: Niall J P
authors.initials: NJ
authors.lastname: McGuinness
authors.affiliation: f Department of Paediatric Dentistry , Edinburgh Dental Institute, University of Edinburgh , Scotland , UK.|g Paediatric Dentistry, King Salman Hospital , Ministry of Health , Riyadh , Saudi Arabia.
authors.forename: Mohammed Saeed
authors.initials: MS
authors.lastname: Aldossary
mesh_terms: D002516:Ceramics; D055117:Curing Lights, Dental; D001840:Dental Bonding; D008422:Materials Testing; D016910:Orthodontic Brackets; D019279:Resin Cements
chemical_list: D019279:Resin Cements
keywords: Ceramic bracket; Vickers-hardness; irradiance; orthodontic adhesive