title: Influence of light transmittance and background reflectance on the light curing of adhesives used to bond esthetic brackets.
abstract: BACKGROUND
  The objectives of this study were to determine the correlation between diffuse light transmittance (DLT) of esthetic brackets and the degree of cure (DC) of light-cured adhesives after direct irradiation, and to evaluate the influence of background reflectance. The influences of curing unit and irradiation time were also determined.
  
  
  METHODS
  The DLT of 4 ceramic and 4 plastic brackets was measured. Two reference light-curing protocols (cured over a glass slab; mean reflectance, 14.7%) and 4 experimental protocols (cured over bovine tooth slab; mean reflectance, 66.5%) were followed with 3 curing units: halogen, plasma arc, and light-emitting diode. The DC of 2 adhesives was calculated based on Fourier transform infrared spectroscopy. Two-way analysis of variance for the DC was performed (P = .05). The Pearson correlation between the DC and the DLT was determined.
  
  
  RESULTS
  Mean DLTs were 44.9% to 75.9%. DC varied by bracket and curing protocol (P <.05) and also by adhesive. In the experimental protocols, there was no significant linear correlation between the DLT and the DC in both adhesives except 1 among 8 groups. The difference in reflectance of background influenced DC (P <.05).
  
  
  CONCLUSIONS
  Based on this clinically simulated model, it was confirmed that the reflectance of the background tooth influenced the DC, instead of the DLT of a bracket. The interaction of the DLT and the reflectance of the background tooth on the light curing of adhesives should be studied further.
authors.affiliation: Department of Orthodontics, Graduate School of Clinical Dentistry, Korea University, Seoul, Korea.
authors.forename: Yong-Kyu
authors.initials: YK
authors.lastname: Lim
authors.forename: Yong-Keun
authors.initials: YK
authors.lastname: Lee
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002417:Cattle; D002516:Ceramics; D003188:Composite Resins / Q000528:radiation effects; D003743:Dental Enamel / Q000502:physiology; D004955:Esthetics, Dental; D008027:Light; D016910:Orthodontic Brackets; D044367:Phase Transition; D010969:Plastics; D011874:Radiometry; D019279:Resin Cements / Q000528:radiation effects*; D012542:Scattering, Radiation; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D003188:Composite Resins; D010969:Plastics; C429652:Reliance Light Bond; D019279:Resin Cements; C477790:Transbond XT