title: Comparison of cytotoxicity test models for evaluating resin-based composites.
abstract: OBJECTIVE
  This study compared different cytotoxicity test models for evaluating resin-based composites (RBCs) and assessed the biocompatibility of standard and bulk-fill RBCs.
  
  
  METHODS
  A standard (spectrum TPH) and a bulk-fill (smart dentin replacement (SDR)) RBC were selected. Disc-shaped specimens (7 mm diameter) of 2 and 4 mm thickness were polymerized for 20 s with a LED curing light of 700 mW/cm2irradiance. The specimens ( n = 5) were subjected to micro-hardness testing and three cytotoxicity test models (direct contact, indirect contact and extract tests) with the established L-929 cell line. Hardness ratios of top and bottom surfaces of specimens were computed to assess the effectiveness of cure. For the direct and indirect contact tests, the cells were stained and zones of inhibition were analyzed after material contact for 24 h. For the extract test, cells were exposed to extracts for 24 h, and cell viability was measured. Data was analyzed using analysis of variance/Scheffe's post hoc test and Pearson's correlation ( p < 0.05).
  
  
  RESULTS
  The lowest mean hardness ratio and highest cytotoxicity were observed for TPH at 4 mm. At 4-mm thickness, SDR was found to be biocompatible with all three models. Correlations between hardness ratio and cell viability ranged from r = 0.89-0.96 for the various tests. A significant correlation ( r = 0.97) was also observed between the three test models.
  
  
  CONCLUSIONS
  Our data indicated consistency between direct contact, indirect contact and extract test models for cytotoxicity testing of RBCs. Bulk placement and curing at 4 mm for the bulk-fill RBC evaluated did not result in undue cytotoxicity.
authors.affiliation: 1 Faculty of Dentistry, National University of Singapore, Singapore.
authors.forename: S M
authors.initials: SM
authors.lastname: Lim
authors.affiliation: 1 Faculty of Dentistry, National University of Singapore, Singapore.|2 Department of Dentistry, Ng Teng Fong General Hospital, Jurong Health Services, Singapore.
authors.forename: Auj
authors.initials: A
authors.lastname: Yap
authors.affiliation: 1 Faculty of Dentistry, National University of Singapore, Singapore.
authors.forename: Csl
authors.initials: C
authors.lastname: Loo
authors.affiliation: 1 Faculty of Dentistry, National University of Singapore, Singapore.
authors.forename: J
authors.initials: J
authors.lastname: Ng
authors.affiliation: 1 Faculty of Dentistry, National University of Singapore, Singapore.
authors.forename: C Y
authors.initials: CY
authors.lastname: Goh
authors.affiliation: 1 Faculty of Dentistry, National University of Singapore, Singapore.
authors.forename: Chl
authors.initials: C
authors.lastname: Hong
authors.affiliation: 1 Faculty of Dentistry, National University of Singapore, Singapore.|3 Tissue Engineering Program, Life Sciences Institute, National University of Singapore, Singapore.
authors.forename: W S
authors.initials: WS
authors.lastname: Toh
mesh_terms: D000818:Animals; D002460:Cell Line; D002470:Cell Survival; D003188:Composite Resins / Q000633:toxicity*; D006244:Hardness; D055115:Light-Curing of Dental Adhesives; D051379:Mice; D018675:Toxicity Tests / Q000379:methods*
chemical_list: D003188:Composite Resins; C000614714:SDR composite; C467914:TPH spectrum
keywords: Cytotoxicity; bulk-fill; resin-based composites; test models