title: Argon ion laser and halogen lamp activation of a dark and light resin composite: microhardness after long-term storage.
abstract: The objective of this study was to evaluate in vitro light activation of the nano-filled resin composite Vita shade A1 and A3 with a halogen lamp (QTH) and argon ion laser by Knoop microhardness profile.
  
  
  METHODS
  Specimens of nanofilled composite resin (Z350-3 M-ESPE) Vita shade A1 and A3 were prepared with a single increment inserted in 2.0-mm-thick and 3-mm diameter disc-shaped Teflon mold. The light activation was performed with QTH for 20 s (with an intensity of approximately 1,000 mW/cm(2) and 700 mW/cm(2)) and argon ion laser for 10 s (with a power of 150 mW and 200 mW). Knoop microhardness test was performed after 24 h and 6 months. The specimens were divided into the 16 experimental groups (n = 10), according to the factors under study: photoactivation form, resin shade, and storage time. Knoop microhardness data was analyzed by a factorial ANOVA and Tukey s tests at the 0.05 level of significance.
  
  
  RESULTS
  Argon ion laser was not able to photo-activate the darker shade of the nanofilled resin composite evaluated but when used with 200 mW it can be as effective as QTH to photo-activate the lighter shade with only 50% of the time exposure. After 6 months storage, an increase in the means of Knoop microhardness values were observed.
  
  
  CONCLUSIONS
  Light-activation significantly influenced the Knoop microhardness values for the darker nanofilled resin composite.
authors.affiliation: Department of Restorative Dentistry, School of Dentistry, Guarulhos University, São Paulo, Brazil. acassoni@prof.ung.br
authors.forename: Alessandra
authors.initials: A
authors.lastname: Cassoni
authors.forename: Juliana de Oliveira
authors.initials: Jde O
authors.lastname: Ferla
authors.forename: Luis Gustavo Barrotte
authors.initials: LG
authors.lastname: Albino
authors.forename: Michel Nicolau
authors.initials: MN
authors.lastname: Youssef
authors.forename: Jamil Awad
authors.initials: JA
authors.lastname: Shibli
authors.forename: José Augusto
authors.initials: JA
authors.lastname: Rodrigues
mesh_terms: D003116:Color; D003188:Composite Resins; D055117:Curing Lights, Dental; D003799:Dental Stress Analysis; D006244:Hardness; D006801:Humans; D066298:In Vitro Techniques; D054020:Lasers, Gas / Q000627:therapeutic use*; D008422:Materials Testing; D013499:Surface Properties; D013997:Time Factors
chemical_list: D003188:Composite Resins