dental materials 27 ( 2 0 1 1 ) 180–186 available at www.sciencedirect.com journal homepage: www.intl.elsevierhealth.com/journals/dema Effect of N-acetyl cysteine on orthodontic primers cytotoxicity Vincenzo D’Antò a,*,1 , Gianrico Spagnuolo a,1 , Helmut Schweikl b , Sandro Rengo a , Luigi Ambrosio c , Roberto Martina a , Rosa Valletta a a Department of Oral and Maxillofacial Sciences, University of Naples “Federico II”, via S. Pansini 5, 80128 Napoli, Italy b Department of Operative Dentistry and Periodontology, University of Regensburg, University Medical Center, D-93042 Regensburg, Germany c Institute of Composite and Biomedical Materials (IMCB), C.N.R., P. le Tecchio 80, 80125 Naples, Italy article info Article history: Received 9 March 2010 Received in revised form 5 May 2010 Accepted 15 October 2010 Keywords: Orthodontic adhesives Cytotoxicity Reactive oxygen species N-acetyl cysteine abstract Objectives. 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 (TC 50 ) in HGF was ranked as follows (median values): Eagle Fluor- sure (0.078 mg/ml) > Transbond XT (0.081 mg/ml) > Transbond MIP (0.128 mg/ml) > Ortho solo (0.130mg/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). Significance. 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. © 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved. ∗ Corresponding author. Tel.: +39 0817462080; fax: +39 0817462080. E-mail address: vincenzo.danto@unina.it (V. D’Antò). 1 These authors equally contributed to the work. 0109-5641/$ – see front matter © 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.dental.2010.10.011