Antibacterial activity and bonding characteristics of an adhesive resin containing antibacterial monomer MDPB Satoshi Imazato a, * , Yoshifumi Kinomoto a , Hisashi Tarumi a , Shigeyuki Ebisu a , Franklin R. Tay b a Department of Restorative Dentistry and Endodontology, Graduate School of Dentistry, Osaka University, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan b Pediatric Dentistry and Orthodontics, Faculty of Dentistry, The University of Hong Kong, Hong Kong SAR, China Received 21 August 2001; revised 22 January 2002; accepted 9 April 2002 Abstract Objectives. The aims of this study were to investigate the antibacterial activity of an adhesive resin incorporating the antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB) as well as its bonding characteristics in terms of bond strength into dentin and curing ability. Methods. An experimental adhesive resin was prepared by incorporation of 2.5% MDPB into proprietary adhesive (LB Bond), and the inhibitory effect of cured specimen against the growth of Streptococcus mutans on its surface was determined. Bond strength to human dentin and degree of conversion of the experimental adhesive in combination with 1, 2, or 5% MDPB-containing primers, which were previously reported to possess bactericidal effect, were evaluated by conventional tensile bond strength test and Fourier transformation infrared spectroscopy. Results. The cured experimental adhesive exhibited an inhibitory effect on S. mutans growth, reducing the number of bacteria to approximately 3% of control adhesive without MDPB. Tensile bond strength of experimental adhesive was not significantly different from that of the control ðp . 0:05Þ; and use in combination with MDPB-containing primer did not show any adverse influence on bond strength. The degree of conversion of the bonding system was not different ðp . 0:05Þ between control and experimental adhesive irrespective of addition of MDPB into primer. Significance. These results indicate that an adhesive resin with antibacterial activity after curing could be produced by incorporation of MDPB without influencing bond strength or curing performance, suggesting that the comprehensive bonding system including MDPB- containing primer and adhesive should be highly effective in its antibacterial effect before and after curing. q 2003 Academy of Dental Materials. Published by Elsevier Science Ltd. All rights reserved. Keywords: Antibacterial activity; Adhesive resin; Bond strength; Curing; Degree of conversion; Adhesive system 1. Introduction Complete sealing at the bonded surface is a pre-requisite for successful restorations as microleakage of bacteria through the gap between restorative material and cavity wall is known to be the main cause of unpleasant symptoms which occur after placement of restorations [1–3]. How- ever, even dentin adhesive systems which show high bond strength have been reported to be incapable of preventing the occurrence of microgaps between the tooth and the restoration in vitro [4]. In fact, scanning electron micro- scopic studies have shown that microgaps existed at the resin/dentin interface in human subjects when recent adhesive systems were used [5–7]. Therefore, dentin bonding systems which possess antibacterial activity even after being placed in the cavity would be beneficial for eliminating the harmful effect caused by bacterial microleakage. Previously, we have reported that incorporation of the antibacterial monomer 12-methacryloyloxydodecylpyridi- nium bromide (MDPB) is an effective method of providing dentin primer with antibacterial activity before and after curing [8,9]. Unpolymerized MDPB has strong antibacterial activity [10], and the primer incorporating MDPB demon- strated bactericidal effect before being cured, indicating the possible ability to kill residual bacteria in the prepared cavity [8]. In addition, resin-based material incorporating MDPB has a unique characteristic to inhibit bacterial growth on its surface after being cured by means of 0109-5641/03/$30.00+0.00 q 2003 Academy of Dental Materials. Published by Elsevier Science Ltd. All rights reserved. PII: S0109-5641(02)00060-X Dental Materials 19 (2003) 313–319 www.elsevier.com/locate/dental * Corresponding author. Tel.: þ 816-6879-2927; fax: þ 816-6879-2929. E-mail address: imazato@dent.osaka-u.ac.jp (S. Imazato).