Biomaterials 26 (2005) 1035–1042 A challenge to the conventional wisdom that simultaneous etching and resin infiltration always occurs in self-etch adhesives Ricardo M. Carvalho a , Stefano Chersoni b , Roland Frankenberger c , David H. Pashley d , Carlo Prati b , Franklin R. Tay e, * a Department of Operative Dentistry, Bauru School of Dentistry, University of S * ao Paulo, Brazil b Department of Dental Sciences, University of Bologna, Bologna, Italy c Policlinic for Operative Dentistry and Periodontology, University of Erlangen-Nuremberg, Gl . uckstraX e 11, Erlangen D-91054, Germany d Department of Oral Biology and Maxillofacial Pathology, School of Dentistry, Medical College of Georgia, Augusta, Georgia, GA 30912-1129, USA e Pediatric Dentistry and Orthodontics, Faculty of Dentistry, The University of Hong Kong, Prince Philip Dental Hospital, 34 Hospital Road, Hong Kong SAR, China Received 20 December 2003; accepted 6 April 2004 Available online 19 May 2004 Abstract This study provided morphological evidence that discrepancies between the depth of demineralisation and the depth of resin infiltration can occur in some mild self-etch adhesives. Sound dentine specimens derived from extracted human third molars were bonded with 5 one-step and 5 two-step self-etch adhesives. One millimeter thick slabs containing the resin–dentine interfaces were immersed in 50 wt% aqueous ammoniacal silver nitrate and processed for TEM examination. A zone of partially etched but uninfiltrated dentine was identified beneath the hybrid layers in the milder versions of both one-step and two-step self-etch adhesives. This zone was characterised by the occurrence of silver deposits along the interfibrillar spaces of mineralised collagen fibrils. The silver infiltrated interfibrillar spaces were clearly identified from the one-step self-etch adhesives Xeno III, iBond, Brush&Bond and the experimental adhesive, and were thinner and only occasionally observed in the two-step self-etch adhesives Clearfil SE Bond and Clearfil Protect Bond. The more aggressive one-step and two-step adhesives that exhibit more abrupt transitions from completely demineralised to mineralised dentin were devoid of these silver-infiltrated interfibrillar spaces beneath the hybrid layers. Incomplete resin infiltration observed in some self-etch adhesives may be caused by the reduced etching potential of the acidic monomers toward the base of hybrid layers, or the presence of acidic but non-polymerisable hydrolytic adhesive components, creating potential sites for the degradation of the bonded created by these self-etch adhesives. r 2004 Elsevier Ltd. All rights reserved. Keywords: Interfibrillar spaces; Self-etch adhesives; Incomplete resin infiltration 1. Introduction Attempt to infiltrate resin monomers into etched dentine created by total-etch adhesives has been shown to be only partially effective. The complete replacement of the rinsing water by adhesive monomers is unattain- able within the short clinical time allowed for this bonding step, and always results in hybrid layers that contain voids [1–3]. Such voids originate from spaces around collagen fibrils that were not enveloped by the infiltrating resin, and are usually located at the bottom of the hybrid layer, just above the mineralised dentine. These voids can be visualised by silver nitrate staining techniques, and have been referred to as nanoleakage [4]. Theoretically, discrepancies between the depth of demineralisation and the depth of resin infiltration can be avoided by the use of self-etching adhesives [5]. They remove minerals from the dentine surface while simul- taneously replacing them with the resin monomers. This process leaves no voids, and consequently, no nanoleak- age would be expected at the interface. However, silver nitrate staining has been reported along resin/dentine ARTICLE IN PRESS *Corresponding author. Tel.: +852-96363673; fax: +852-25593803. E-mail address: kfctay@netvigator.com (F.R. Tay). 0142-9612/$ - see front matter r 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.biomaterials.2004.04.003