title: Cytotoxicity of post and core composites as a function of environmental conditions.
abstract: OBJECTIVE
  In the revised version of ISO 7405 there are so far no detailed recommendations concerning temperature and humidity during specimen production for light curing and chemically setting dental materials. The main objective of the present study was to observe if different environmental conditions during specimen production influence cytotoxicity and degree of conversion of four post and core composite materials and to investigate if cytotoxicity of post and core materials is influenced by their corresponding bonding substances.
  
  
  METHODS
  Specimens of four different post and core composite materials (LuxaCore - Dual, Core X-Flow, Flow White and MultiCore Flow) were produced in a climate test chamber at 23°C/50% relative humidity or 37°C/95% relative humidity and were dual-cured or self-cured, with or without their corresponding bonding substances. Specimens were added to cell cultures immediately after production or after preincubation for 7 days. Specimens were incubated with L-929 fibroblasts for 72h and cell numbers determined by a flow cytometer. FTIR spectroscopic measurements of post and core materials were performed at the same temperature conditions as for the cytotoxicity assay (23°C or 37°C).
  
  
  RESULTS
  Dual-cured specimens of all post and core composites exhibited less cytotoxicity under both environmental conditions than self-cured specimens. All self-cured specimens manufactured at 37°C/95% showed less cytotoxicity than specimens produced at 23°C/50%. All dual-cured specimens showed similar cytotoxicity at both environmental conditions. After 7 days of preincubation most dual-cured specimens produced at 23°C/50% showed less cytotoxicity than self-cured specimens (with the exception of Flow White). Compared to fresh specimens, 7-day aged specimens of most materials showed reduced cytotoxicity. Materials already showing low cytotoxicity as fresh specimens did not further reduce their cytotoxicity after 7 days of preincubation. For dual-cured materials the degree of conversion was higher compared to self-cured materials.
  
  
  CONCLUSIONS
  Different temperatures during specimen production have an impact on cytotoxicity and degree of conversion of dual-curing composite materials. Detailed recommendations for standardization concerning environmental conditions during specimen production are required.
authors.affiliation: Competence Center for Dental Materials, Bernhard Gottlieb University Clinic of Dentistry, Vienna, Austria.
authors.forename: Alexander
authors.initials: A
authors.lastname: Franz
authors.affiliation: Spinell T: Division of Periodontics, Section of Oral and Diagnostic Sciences, Columbia University College of Dental Medicine, NY, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Spinell
authors.affiliation: Graf A: Center for Medical Statistics, Informatics and Intelligent Systems, Medical University of Vienna, Vienna, Austria.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Graf
authors.affiliation: Wutzel H: Institute of Applied Synthetic Chemistry, Vienna University of Technology, Vienna, Austria.
authors.forename: Harald
authors.initials: H
authors.lastname: Wutzel
authors.affiliation: Liska R: Institute of Applied Synthetic Chemistry, Vienna University of Technology, Vienna, Austria.
authors.forename: Robert
authors.initials: R
authors.lastname: Liska
authors.affiliation: Watts DC: University of Manchester, School of Dentistry and Photon Science Institute, Oxford Road, Manchester M13 9PL, UK.
authors.forename: David C
authors.initials: DC
authors.lastname: Watts
authors.affiliation: Competence Center for Dental Materials, Bernhard Gottlieb University Clinic of Dentistry, Vienna, Austria.
authors.forename: Andreas
authors.initials: A
authors.lastname: Moritz
authors.affiliation: Competence Center for Dental Materials, Bernhard Gottlieb University Clinic of Dentistry, Vienna, Austria. Electronic address: andreas.schedle@meduniwien.ac.at.
authors.forename: Andreas
authors.initials: A
authors.lastname: Schedle
mesh_terms: D000818:Animals; D002460:Cell Line; D003188:Composite Resins; D051379:Mice; D011176:Post and Core Technique
chemical_list: D003188:Composite Resins
keywords: Biocompatibility; Degree of conversion; Dental bonding substances; Dental post and core composites; Fibroblasts; Toxicology