Effect of 2% chlorhexidine on dentin microtensile bond strengths and nanoleakage of luting cements N. Hiraishi a, *, C.K.Y. Yiu a , N.M. King a , F.R. Tay b a Paediatric Dentistry and Orthodontics, Faculty of Dentistry, The University of Hong Kong, Prince Philip Dental Hospital, 34 Hospital Road, Pokfulam, Hong Kong SAR, China b Department of Endodontics, School of Dentistry, Medical College of Georgia, Augusta, Georgia, USA 1. Introduction Incomplete removal of caries-infected enamel or dentine during cavity preparation 1,2 results in the entrapment of active bacteria which may continue to multiply within the cavity. These bacteria can produce toxins that diffuse into the pulp, causing pulpal irritation and inflammation. 1 Pre-treatment of the tooth surface with an antibacterial agent is useful in eliminating the harmful effects caused by either the residual bacteria or by bacterial microleakage. 3 Chlorhexidine has a broad spectrum of action against both Gram-positive and Gram-negative microbes, although it is less effective with the latter. 2 Because of its antibacterial action, chlorhexidine application to cavity prior to placement of the restoration had been recommended. 4–6 In addition to its antibacterial effect, chlorhexidine also functions as a potent MMP inhibitor. 7 Chlorhexidine has recently been shown to have an inhibitory effect on the journal of dentistry 37 (2009) 440–448 article info Article history: Received 22 April 2008 Received in revised form 15 January 2009 Accepted 3 February 2009 Keywords: Resin cement Nanoleakage Microtensile bond strength SEM Chlorhexidine Dentine disinfectant abstract Objectives: The aim of this study was to investigate the effect of pre-treatment by chlorhex- idine on the microtensile bond strength (mTBS) of resin cements and nanoleakage at the resin–dentine interfaces. Methods: Cylindrical composite blocks were luted to human dentine using resin cements (RelyX ARC, 3M ESPE: ARC; Panavia F, Kuraray Medical Inc.: PF; RelyX Unicem, 3M ESPE: UN) with/without pre-treatment by 2% chlorhexidine digluconate (CAVITY CLEANSER, Bisco, Inc., Schaumburg, IL, USA). CAVITY CLEANSER was applied on the acid etched dentine for 60 s in the ARC group, and on smear layer-covered dentine in the PF and UN groups. After storage in water for 24 h, the bonded teeth were sectioned into 1 mm thick slabs and further into 0.9 mm  0.9 mm beams. After immersion in water or ammoniacal silver nitrate for 24 h, the beams were stressed to failure in tension. The fractured surfaces were examined by field-emission scanning electron microscopy (FE-SEM) using backscattered electron mode. The silver-stained slabs were used to examine nanoleakage within the bonded interface by FE-SEM. Results: The resin cement and chlorhexidine treatment had significant effects ( p < 0.0001) on mTBS; while the storage media had no significant effect ( p = 0.435). The mTBS of ARC was significantly higher than the other cements. Chlorhexidine reduced mTBS and produced pronounced nanoleakage when PF and UC were luted to dentine. Conclusions: Pre-treatment with chlorhexidine affected the integrity of dentine bonding with PF and UC, while there was no adverse effect on coupling of ARC. # 2009 Elsevier Ltd. All rights reserved. * Corresponding author. Tel.: +852 28590251; fax: +852 25593803. E-mail address: hiraishinoriko@yahoo.com (N. Hiraishi). available at www.sciencedirect.com journal homepage: www.intl.elsevierhealth.com/journals/jden 0300-5712/$ – see front matter # 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.jdent.2009.02.002