title: Biocompatibility and cytotoxicity of two novel low-shrinkage dental resin matrices.
abstract: OBJECTIVE
  To reduce the polymerization shrinkage of dental composite resin, we used two different ratios of toluene 2,4-diisocyanate (TDI) or 1,6-hexamethylene diisocyanate (HDI) as functional side chains of bisphenol A-glycidyl methacrylate (bis-GMA) to synthesize two series of new dental resin matrices. This study evaluated the biocompatibility and cytotoxicity of these two series of new resin matrices.
  
  
  METHODS
  Two series of new dental resin matrices with the ratios of TDI or HDI functional side chain to bis-GMA (defined as B group) being 1:4, 1:2, 1:1 and 3:2 (defined as T1/4, T1/2, T1, T3/2, and H1/4, H1/2, H1, H3/2 groups, respectively) were synthesized. Each resin sample was light cured and immersed in the culture medium for 24 hours to make the extract solution. Then, human gingival fibroblasts were cultured in different extract solutions for 72 hours. The cytotoxicities of different resins were evaluated by microtitertetrazolium (MTT) assay, the levels of cell-produced reactive oxygen species (ROS) induced by different extract solutions was measured.
  
  
  RESULTS
  Resins of the T1/4 and B groups revealed significantly higher cytotoxicity than resins of other groups. However, resins of the T1 and T3/2 groups exhibited less cytotoxicity. In general, resins of the TDI-modified groups showed equal or less cytotoxicity and induced equal or lower levels of ROS than the corresponding resins of the HDI-modified and B groups.
  
  
  CONCLUSIONS
  Our results showed that the TDI-modified resin matrices containing more functional side chains were less cytotoxic than the corresponding HDI-modified resin matrices. When the ratio of functional side chain to bis-GMA is increased, the stereo hindrance of resin structure is increased, more toxic resin monomers are trapped in the complicated resin structure, and thus the resin matrix reveals less cytotoxicity. The TDI-modified resin matrices exhibit higher stereo hindrance of resin structure and thus show less cytotoxicity than the corresponding HDI-modified resin matrices.
authors.affiliation: Graduate Institute of Clinical Dentistry, National Taiwan University, Taipei, Taiwan.
authors.forename: Yih-Dean
authors.initials: YD
authors.lastname: Jan
authors.affiliation: Graduate Institute of Oral Biology, National Taiwan University, Taipei, Taiwan; School of Dentistry, National Taiwan University, Taipei, Taiwan.
authors.forename: Bor-Shiunn
authors.initials: BS
authors.lastname: Lee
authors.affiliation: Graduate Institute of Clinical Dentistry, National Taiwan University, Taipei, Taiwan; Graduate Institute of Oral Biology, National Taiwan University, Taipei, Taiwan; School of Dentistry, National Taiwan University, Taipei, Taiwan; Department of Dentistry, National Taiwan University Hospital, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Chun-Pin
authors.initials: CP
authors.lastname: Lin
authors.affiliation: School of Dentistry, National Taiwan University, Taipei, Taiwan; Department of Dentistry, National Taiwan University Hospital, College of Medicine, National Taiwan University, Taipei, Taiwan. Electronic address: yeshes@gmail.com.
authors.forename: Wan-Yu
authors.initials: WY
authors.lastname: Tseng
mesh_terms: D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D006801:Humans; D017953:Isocyanates / Q000737:chemistry; D008422:Materials Testing; D017382:Reactive Oxygen Species / Q000378:metabolism; D012117:Resins, Synthetic / Q000737:chemistry / Q000494:pharmacology; D014051:Toluene 2,4-Diisocyanate / Q000737:chemistry
chemical_list: D017953:Isocyanates; D017382:Reactive Oxygen Species; D012117:Resins, Synthetic; C015262:1,6-hexamethylene diisocyanate; D014051:Toluene 2,4-Diisocyanate
keywords: biocompatibility; cytotoxicity; reactive oxygen species; resin matrix