title: Influence of irradiance on the push-out bond strength of composite restorations photoactivated by LED.
abstract: OBJECTIVE
  The aim of this study was to compare the bond strength of resin composites to dental structure photoactivated with a light emitting diode (LED) curing unit.
  
  
  METHODS
  One hundred bovine incisors were selected and a conical cavity was prepared in the facial surface of each tooth. Clearfil SE Bond (Kuraray CO., LTD. Osaka, Japan) adhesive system was applied, and the cavities were filled with a single increment of Filtektrade mark Z250 (3M ESPE, St. Paul, MN, USA) or Esthet-X (Dentsply-Caulk - Mildford, DE, USA). The specimens were assigned to ten groups (n=10) according to the irradiance used: 100, 200, 300, 400, or 500 mW/cm(2). Photoactivation was accomplished using an Ultrablue IS LED (DMC Equipamentos LTDA, São Carlos, SP, Brazil). The radiant exposure time was kept constant. A push-out test was conducted in a universal testing machine. Bond strength values were submitted to a two-way analysis of variance (ANOVA) and a Tukey's test at the 5% significance level.
  
  
  RESULTS
  The bond strength of the Z250 was higher than the Eshet-X (p<0.05). However, the modulation of irradiance adjusted to the same radiant exposure had no influence on Z250. The bond strength using an irradiance of 100mW/cm(2) was higher than the other levels for Esthet-X. When composites were compared, no significant differences were detected between them for activation with irradiances of 100 and 200 mW/cm(2).
  
  
  CONCLUSIONS
  The modulation of the luminous energy emitted by LED was almost unable to provide significant differences among the groups for both composites, except for a lower irradiance of Esthet-X.
authors.affiliation: Department of Restorative Dentistry, Dental Materials Division, of the State University of Campinas in Piracicaba, SP, Brazil. draxse@fop.unicamp.br
authors.forename: Dario
authors.initials: D
authors.lastname: Segreto
authors.forename: William Cunha
authors.initials: WC
authors.lastname: Brandt
authors.forename: Lourenco
authors.initials: L
authors.lastname: Correr-Sobrinho
authors.forename: Mario Alexandre Coelho
authors.initials: MA
authors.lastname: Sinhoreti
authors.forename: Simonides
authors.initials: S
authors.lastname: Consani
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002417:Cattle; D003188:Composite Resins / Q000528:radiation effects*; D001840:Dental Bonding; D003799:Dental Stress Analysis; D008027:Light; D019279:Resin Cements; D012666:Semiconductors; D018709:Statistics, Nonparametric; D013997:Time Factors
chemical_list: C438313:Clearfil SE Bond; D003188:Composite Resins; C466112:Esthet-X; C444701:Filtek Z250; D019279:Resin Cements