Degradation of resin – dentin bonds using NaOCl storage M. Yamauti a , M. Hashimoto b, * , H. Sano c , H. Ohno d , R.M. Carvalho a , M. Kaga b , J. Tagami e , H. Oguchi b , M. Kubota f a Department of Operative Dentistry, Bauru School of Dentistry, University of Sa ˜o Paulo, SP, Brazil b Division of Pediatric Dentistry, Graduate School of Dental Medicine, Hokkaido University, Hokkaido, Japan c Division of Cariology and Endodontology, Graduate School of Dental Medicine, Hokkaido University, Hokkaido, Japan d Department of Dental Materials Science, School of Dentistry, Health Sciences University of Hokkaido, Hokkaido, Japan e Department of Restorative Sciences, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan f Department of Operative Dentistry and Endodontics, School of Dentistry, Iwate Medical University, Iwate, Japan Received 26 September 2001; revised 15 April 2002; accepted 13 June 2002 Abstract Objectives. Several recent studies have reported collagen hydrolysis within bonds over the long-term. This may be one reason for the degradation of the bonds. This study therefore aimed to determine the effects of NaOCl on adhesive system bonds (total-etch bonding system vs. self-etching primer system) to dentin in order to accelerate the durability testing. Methods. Resin – dentin bonded specimens were produced using Liner Bond 2V (Kuraray), a self-etching primer system, and OptiBond SOLO (Kerr), a total-etch bonding system, according to the manufacturers’ instructions. The bonded specimens were serially sectioned in both x and y directions across the adhesive interface to obtain beams (adhesive area: 0.9 mm 2 ). The specimens were immersed in 10% NaOCl solution for 1–5 h after being stored in water at 37 8C for 24 h. Control specimens were tested without exposure to NaOCl. After storage, micro-tensile bond tests were performed. Results were analyzed by two-way ANOVA and Fisher’s PLSD tests ( p , 0.05). All fractured surfaces were observed by SEM, and examined using an image analyzer. Results. The bond strengths decreased with increasing storage time in NaOCl. Fractography showed that NaOCl had a greater effect on the bond structure of OptiBond SOLO than on that of Liner Bond 2V, although both adhesives were susceptible. Significance. Deterioration of the bonds was responsible for the effect of NaOCl on the hybrid layer. This deterioration may occur in humans in cases of deproteinization within the bonds. q 2003 Academy of Dental Materials. Published by Elsevier Science Ltd. All rights reserved. Keywords: NaOCl storage; Hybrid layer; Microtensile bond test; Total-etch bonding system; Self-etching primer system; Durability 1. Introduction In an attempt to simplify the bonding procedure, several single bottle primer-adhesive systems have recently been introduced to reduce the clinical steps in bonding pro- cedures. These newly developed systems can be divided into two types: total-etch bonding systems (single bottle) and self-etching primer systems. In a total-etch bonding system, the priming agent and the adhesive resin are combined into a single component that is applied after acid etching and water rinsing. At the time of resin application, the acidified dentin surface is left wet to promote the resin infiltration into the collagen network [1]. In the self-etching primer system, a combined etching/priming agent is applied but not rinsed off, and then a low-viscosity resin layer is applied. Theoretically, in order to promote optimal bonding and sealing, the resin should completely diffuse across the full thickness of the etched dentin. This would encapsulate and protect the collagen fibril, fill interfibrillar spaces and permit physical interaction with the unaltered underlying dentin. Recently, several studies using total-etch bonding systems have suggested that a demineralized and non-protected dentin zone remains below the hybridized layer, due to incomplete resin infiltration [2–6]. Some long-term in vitro studies [7–9], using water as the storage medium, have demonstrated that the decrease in bond strength over time was not uniform for all materials tested. That is, the rate of 0109-5641/03/$ - see front matter q 2003 Academy of Dental Materials. Published by Elsevier Science Ltd. All rights reserved. doi:10.1016/S0109-5641(02)00083-0 Dental Materials 19 (2003) 399–405 www.elsevier.com/locate/dental * Corresponding author. Address: Department of Pediatric Dentistry, School of Dentistry, Hokkaido University, North 13, West 7, Kita-ku, Sapporo 060-8586, Japan. Tel.: þ81-11-706-4292; fax: þ81-11-706-4307. E-mail address: masanori-h@mue.biglobe.ne.jp (M. Hashimoto).