title: Microhardness of composite resins at different depths varying the post-irradiation time.
abstract: OBJECTIVE
  The purpose of this study was to assess the microhardness of posterior composite resins at different depths varying the post-irradiation time.
  
  
  METHODS
  For each composite resin [Solitaire 2 (SO) - Heraus Kulzer, P60 (P) - 3M, Prodigy Condesable (PC) - Kerr, Surefil (S) - Dentsply and Alert (A) - Pentron], 6 specimens (3 mm in diameter; 4 mm high) were prepared using a black polyurethane cylindrical matrix. The resins were inserted in a bulk increment and light cured for 40 seconds. Microhardness was analyzed at different depths (top, 0.4 mm, 1.0 mm, 2.0 mm, 3.0 mm and 4.0 mm) and at two moments (20 minutes and 24 hours after light-curing). Data were analyzed by ANOVA and Tukey's test (p<0.05).
  
  
  RESULTS
  Overall, microhardness means decreased significantly with the increase of depth, being lower in the first moment tested. P, S and PC showed the highest microhardness means.
  
  
  CONCLUSIONS
  It may be concluded that the tested composite resins presented a gradual decrease of microhardness as depth increased and this drop was more accentuated for depths beyond 2 mm. For all materials, higher microhardness means were recorded 24 hours after light activation. P60 yielded the best results at the different depths evaluated.
authors.affiliation: Department of Restorative Dentistry, School of Dentistry of Ribeirão Preto, University of São Paulo, Ribeirão Preto, São Paulo, Brazil.
authors.forename: Juliane Cristina
authors.initials: JC
authors.lastname: Ciccone-Nogueira
authors.forename: Mariana Cristina
authors.initials: MC
authors.lastname: Borsatto
authors.forename: Wanessa Christine
authors.initials: WC
authors.lastname: de Souza-Zaron
authors.forename: Renata Pereira
authors.initials: RP
authors.lastname: Ramos
authors.forename: Regina Guenka
authors.initials: RG
authors.lastname: Palma-Dibb