title: The effect of light curing units and modes on cytotoxicity of resin-core systems.
abstract: OBJECTIVE
  The aim of this study was to compare the cytotoxic effects of various resin-based core materials that were cured with three light curing units (LCUs) in different modes on L-929 mouse fibroblast cells over 24 h and 72 h periods.
  
  
  METHODS
  Eighty-four cylindrical discs (2 mm in thickness and 6 mm in diameter) of each material (Rebilda, Voco; Build-It FR, Pentron; Clearfil DC Core, Kuraray and Bis-core, Bisco) were cured by QTH LCU (soft-up and high-power modes), LED LCU (exponential and standard modes) and PAC LCU (normal and ramp-curing modes). Then the samples were aged for 24 and 72 hours in Dulbecco's Modified Eagle Medium/Ham's F12 (DMEM/F12). After each ageing interval, cytotoxicity of the extracts to cultured fibroblasts (L 929) was measured by MTT assay. The degree of cytotoxicity for each sample was determined according to the reference value represented by the cells with a pure culture medium. Statistical significance was determined by a multifactorial analysis of variance followed by one-way ANOVA and Tukey's post-hoc test or independent t tests.
  
  
  RESULTS
  Data showed that there are significant differences among resin based core materials, LCUs, curing modes and time factors (p<0.001). The test materials cured with the QTH and LED demonstrated statistically higher cell survival rates when compared with those cured with the PAC (p<0.001).
  
  
  CONCLUSIONS
  Differential toxic effects of the resin-based core materials cured with QTH, LED and PAC on the fibroblast cells may prove to be very important when suitable resin-core systems, LCUs and curing modes are used for operative restorations.
authors.affiliation: Department of Prosthodontics, Faculty of Dentistry, Gazi University, Ankara, Turkey. ergungulfem@yahoo.com
authors.forename: Gulfem
authors.initials: G
authors.lastname: Ergun
authors.forename: Ferhan
authors.initials: F
authors.lastname: Egilmez
authors.forename: Isil
authors.initials: I
authors.lastname: Cekic-Nagas
mesh_terms: D000818:Animals; D055117:Curing Lights, Dental; D005347:Fibroblasts / Q000187:drug effects*; D051379:Mice; D012117:Resins, Synthetic / Q000633:toxicity*
chemical_list: D012117:Resins, Synthetic