title: Effect of N-acetyl cysteine on orthodontic primers cytotoxicity.
abstract: OBJECTIVE
  The aims of this study were to evaluate the cytotoxicity of four orthodontic primers, including two hydrophilic and two hydrophobic materials, and to investigate the role of the reactive oxygen species (ROS) in induced cell damage. Moreover, the effects of the anti-oxidant N-acetyl cysteine (NAC) on primers toxicity was analyzed.
  
  
  METHODS
  Human gingival fibroblasts (HGF) were exposed to different concentrations of primers (0-0.25 mg/ml) in the presence or absence of NAC, and the cytotoxicity was assessed by the MTT assay, while cell death was quantified by flow cytometry after propidium iodide staining. The increase in the induced ROS levels was detected by flow cytometry measuring the fluorescence of the oxidation-sensitive dye 2',7'-dichlorofluorescein diacetate (DCFH-DA).
  
  
  RESULTS
  All materials decreased cell viability in a dose-related manner after a 24 h exposure period. Cytotoxicity of orthodontic primers based on concentrations which caused a 50% decrease in cell viability (TC₅₀) in HGF was ranked as follows (median values): Eagle Fluorsure (0.078 mg/ml)>Transbond XT (0.081 mg/ml)>Transbond MIP (0.128 mg/ml)>Ortho solo (0.130 mg/ml). Moreover, in HGF cells, all materials induced a dose-dependent increase in ROS levels compared to untreated cells. Incubation of HGF with NAC significantly reduced ROS production and decreased the cell damage and cytotoxicity caused by all materials tested (p<0.001).
  
  
  CONCLUSIONS
  Our results suggested that hydrophilic primers were less cytotoxic than hydrophobic materials. Moreover, we demonstrated a major role of ROS in the induction of cell death since the antioxidant N-acetyl cysteine was able to prevent cell damage induced by all materials tested.
authors.affiliation: Department of Oral and Maxillofacial Sciences, University of Naples Federico II, via S. Pansini 5, 80128 Napoli, Italy. vincenzo.danto@unina.it
authors.forename: Vincenzo
authors.initials: V
authors.lastname: D'Antò
authors.forename: Gianrico
authors.initials: G
authors.lastname: Spagnuolo
authors.forename: Helmut
authors.initials: H
authors.lastname: Schweikl
authors.forename: Sandro
authors.initials: S
authors.lastname: Rengo
authors.forename: Luigi
authors.initials: L
authors.lastname: Ambrosio
authors.forename: Roberto
authors.initials: R
authors.lastname: Martina
authors.forename: Rosa
authors.initials: R
authors.lastname: Valletta
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology*; D000975:Antioxidants / Q000494:pharmacology*; D016923:Cell Death / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004396:Coloring Agents; D017220:Dentin-Bonding Agents / Q000633:toxicity; D004305:Dose-Response Relationship, Drug; D000431:Ethanol / Q000633:toxicity; D005347:Fibroblasts / Q000187:drug effects*; D005434:Flow Cytometry; D005452:Fluoresceins; D005456:Fluorescent Dyes; D005881:Gingiva / Q000166:cytology / Q000187:drug effects*; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008689:Methacrylates / Q000633:toxicity; D011419:Propidium; D017382:Reactive Oxygen Species / Q000633:toxicity*; D019279:Resin Cements / Q000633:toxicity*; D013778:Tetrazolium Salts; D013844:Thiazoles
chemical_list: D000975:Antioxidants; D004396:Coloring Agents; D017220:Dentin-Bonding Agents; D005452:Fluoresceins; D005456:Fluorescent Dyes; D008689:Methacrylates; C508972:OrthoSolo; D017382:Reactive Oxygen Species; D019279:Resin Cements; D013778:Tetrazolium Salts; D013844:Thiazoles; C477790:Transbond XT; C458821:Transbond moisture-insensitive primer; C029569:diacetyldichlorofluorescein; D011419:Propidium; D000431:Ethanol; C022616:thiazolyl blue; D000111:Acetylcysteine