title: Setting properties and cytotoxicity evaluation of a premixed bioceramic root canal sealer.
abstract: BACKGROUND
  This study investigated the setting time and micohardness of a premixed calcium phosphate silicate-based sealer (EndoSequence BC Sealer; Brasseler USA, Savannah, GA) in the presence of different moisture contents (0-9 wt%). The moisture content that produced the most optimal setting properties was used to prepare set EndoSequence BC Sealer for cytotoxicity comparison with an epoxy resin-based sealer (AH Plus; Dentsply Caulk, Milford, DE).
  
  
  METHODS
  Standardized disks were created with BC Sealer, AH Plus, Pulp Canal Sealer EWT (positive control) (SybronEndo, Orange CA), and Teflon (Small Parts Inc., Miami Lakes, FL; negative control). Disks were placed in Transwell Inserts, providing indirect contact with MC3T3-E1 cells. Succinate dehydrogenase activity of the cells was evaluated over a 6-week period using MTT ((3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Cytotoxicity profiles of BC Sealer and AH Plus were fitted with polynomial regression models. The time for 50% of the cells to survive (T(0.5)) was analyzed using the Wald statistic with a two-tailed significance level of 0.05.
  
  
  RESULTS
  BC Sealer required at least 168 hours to reach the final setting using the Gilmore needle method, and its microhardeness significantly declined when water was included in the sealer (P = .004). All set sealers exhibited severe cytotoxicity at 24 hours. The cytotoxicity of AH Plus gradually decreased and became noncytotoxic, whereas BC Sealer remained moderately cytotoxic over the 6-week period. A significant difference (P < .001) was detected between T(0.5) of BC Sealer (5.10 weeks; 95% confidence interval [CI], 4.69-5.42, standard error [SE] = 0.09) and T(0.5) of AH Plus (0.86 weeks; 95% CI, 0.68-1.05; SE = 0.18).
  
  
  CONCLUSIONS
  Further studies are required to evaluate the correlation between the length of setting time of BC Sealer and its degree of cytotoxicity.
authors.affiliation: Department of Endodontics, Medical College of Georgia, Augusta, GA, USA.
authors.forename: Bethany A
authors.initials: BA
authors.lastname: Loushine
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Bryan
authors.forename: Stephen W
authors.initials: SW
authors.lastname: Looney
authors.forename: Brian M
authors.initials: BM
authors.lastname: Gillen
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Loushine
authors.forename: R Norman
authors.initials: RN
authors.lastname: Weller
authors.forename: David H
authors.initials: DH
authors.lastname: Pashley
authors.forename: Franklin R
authors.initials: FR
authors.lastname: Tay
mesh_terms: D016475:3T3 Cells; D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry* / Q000633:toxicity; D002130:Calcium Phosphates / Q000737:chemistry / Q000633:toxicity; D002470:Cell Survival / Q000187:drug effects; D002516:Ceramics / Q000737:chemistry* / Q000633:toxicity; D004396:Coloring Agents; D004338:Drug Combinations; D004853:Epoxy Resins / Q000737:chemistry / Q000633:toxicity; D006244:Hardness; D008422:Materials Testing; D051379:Mice; D010006:Osteoblasts / Q000187:drug effects; D010087:Oxides / Q000737:chemistry / Q000633:toxicity; D011138:Polytetrafluoroethylene / Q000737:chemistry / Q000633:toxicity; D012387:Root Canal Filling Materials / Q000737:chemistry* / Q000633:toxicity; D017640:Silicates / Q000737:chemistry / Q000633:toxicity; D013385:Succinate Dehydrogenase / Q000032:analysis; D013778:Tetrazolium Salts; D013844:Thiazoles; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: D001672:Biocompatible Materials; D002130:Calcium Phosphates; D004396:Coloring Agents; D004338:Drug Combinations; C550603:EndoSequence root repair material; D004853:Epoxy Resins; D010087:Oxides; D012387:Root Canal Filling Materials; D017640:Silicates; D013778:Tetrazolium Salts; D013844:Thiazoles; C534916:epoxy resin-based root canal sealer; D014867:Water; D011138:Polytetrafluoroethylene; D013385:Succinate Dehydrogenase; C022616:thiazolyl blue