Improving the Quality of the Quartz Fiber Postcore Bond Using Sodium Ethoxide Etching and Combined Silane/ Adhesive Coupling Francesca Monticelli,* Raquel Osorio, † Manuel Toledano, † Cecilia Goracci,* Franklin R. Tay,* ‡ and Marco Ferrari* Abstract The influence of different silane/dentin adhesives on the microtensile bond strengths of a hybrid composite to sodium ethoxide-etched quartz fiber posts was in- vestigated. A prehydrolyzed silane was applied without an adhesive and compared to two-component systems in which hydrolysis of the silane occurred after mixing with the acidic monomer present in the dentin adhe- sives. Nanoleakage along post/core interfaces was ex- amined after silver nitrate tracer penetration using scanning electron microscopy. Higher interfacial strengths and more uniform adaptation between the etched fiber post surface and the composite core were recorded after post treatment with silane/adhesive cou- plings. The combination of silane with two-step self- etch adhesives improves the chemical retention of com- posites around etched fiber posts with minimal nanoleakage. Although the one-step self-etching adhe- sive/silane combination enhances post adhesion, the extensive nanoleakage provides channels for rapid wa- ter sorption that may expedite hydrolytic degradation of the post/core interface. (J Endod 2006;32:447– 451) Key Words Acidic monomer, core build-up, fiber post, silane cou- pling, silver nitrate F iber posts are commonly employed for restoring endodontically treated teeth (1, 2). Although in vivo studies of post/core restorations demonstrated satisfactory clinical results (3), further improvement in the adhesion between fiber posts and composite resins is desirable to optimize the durability of these restorations (4). The use of silane coupling agents as adhesion promoters in fiber-reinforced ma- terials is well established (5, 6). Trialkoxy silanes have the general formula RYSiX 3, where R is a nonhydrolyzable functional group, Y a linker and X the hydrolyzable group. The nonhydrolyzable group (e.g. methacrylate) can polymerize with resin composite monomers containing C = C double bonds. The alkoxy groups (X) can form chemical bonds with inorganic substrates with hydroxyl groups, such as the silica surface, form- ing chemical bonds (7, 8). Recent studies on the silanization of translucent fiber posts before core build-up have been promising (9, 10). Bonding to etchable ceramics is usually achieved by etching the ceramic surface to increase the surface area for micromechanical retention and silane coupling (11). A similar approach may be used to render the surfaces of epoxy-resin based fiber posts more conducive to silanization. Etching solutions such as sodium ethoxide or hydrogen peroxide commonly employed for partially removing the resinous superficial layer of resin-embedded tissue sections to enhance immunolabeling may be adopted for surface etching of fiber posts containing epoxy resin matrix (12, 13). The possibility of com- bining a silane/primer solution and a bonding agent has been recently shown to im- prove bond strength to ceramics (14, 15). Microtensile bond strength and nanoleakage evaluations have generally been used for evaluating the integrity of bonded dentin interfaces (16, 17). Silver nitrate is a powerful tracer used to assess the existence of a microporous zone within or beneath dentin-resin hybrid layers (18). The purpose of the present study was to examine the effect of different combinations of silane coupling and bonding agents on the adhesion of etched fiber posts to a resin composite core material. The null hypothesis tested was that there are no differences on the adhesive strengths of different silane/resin-based couplings when they are applied for bonding fiber post to a composite core material. Materials and Methods Experimental Design Forty-two quartz fiber posts (DT Light Post #3, RTD, St. Egève, France) were used for testing. DT Light Posts contain pretensed quartz fibers (60%) embedded in an epoxy resin matrix (40%). All posts were pretreated with 21 wt% sodium ethoxide solution in ethanol (Sigma, Aldrich Chemicals, GmbH, Steinheim, Germany) for 20 min to remove the surface epoxy resin and expose the quartz fibers (12, 13). After etching, the fiber posts were rinsed consecutively with absolute ethanol (Panreac Quimica SA, Barcelona, Spain), 50% ethanol and deionized water (P Selecta S.A. Abrera, Barcelona Spain) until a stable pH of 7 was achieved. To ensure thorough cleaning, all posts were ultrasonically cleaned for 10 min in deionized water, immersed in 96% ethanol and dried with an oil-free air. The posts were divided into six experimental groups (n = 7 posts each) according to the silane/adhesive coupling agent tested on the post surface: From the *Department of Restorative Dentistry and Dental Materials, University of Siena, Italy; † Department of Dental Materials, University of Granada, Spain; ‡ Department of Oral Biology & Maxillofacial Pathology, School of Dentistry, Med- ical College of Georgia, Augusta, Georgia. Address requests for reprint to Monticelli Francesca, De- partment of Restorative Dentistry and Dental Materials, Uni- versity of Siena, Policlinico Le Scotte, Viale Bracci, 53100 Siena, Italy. E-mail address: francescamonti@hotmail.it. 0099-2399/$0 - see front matter Copyright © 2006 by the American Association of Endodontists. doi:10.1016/j.joen.2005.10.061 Basic Research—Technology JOE — Volume 32, Number 5, May 2006 Improving Quartz Fiber Postcore Bond Quality 447