Effects of Sodium Hypochlorite Gel and Sodium Hypochlorite Solution on Dentin Bond Strength Vanessa G. Arias, Ana Karina B. Bedran-de-Castro, Luiz Andre ´ Pimenta Department of Restorative Dentistry, School of Dentistry of Piracicaba University of Campinas (UNICAMP), Av. Limeira, 901, 13414-018, Piracicaba/SP, Brazil Received 28 April 2004; revised 15 July 2004; accepted 21 July 2004 Published online 15 October 2004 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/jbm.b.30160 Abstract: The aim of this study was to determine the effect of 10% NaOCl gel and 10% NaOCl solution on dentin bond strengths of four adhesive systems. One hundred eighty bovine incisors were ground to achieve a flat polished surface, then divided into 12 groups: Gluma One Bond [G1 - control; G2 - NaOCl solution; G3 - NaOCl gel]; Prime & Bond 2.1 [G4 - control; G5 - NaOCl solution; G6 - NaOCl gel]; Single Bond [G7 - control; G8 - NaOCl solution; G9 - NaOCl gel]; Prime & Bond NT [G10 - control; G11 - NaOCl solution; G12 - NaOCl gel]. Dentin was etched, rinsed, and blot dried. For the experimental groups, after acid etching, 10% NaOCl solution or 10% NaOCl gel was applied for 60 s, rinsed, and blot dried. Composite resin was inserted and light cured. Shear bond strengths were tested with a crosshead speed of 0.5mm/min. The mean values MPa (SD) were analyzed with two-way ANOVA and Tukey’s tests ( < 0.01). Ten percent NaOCl solution significantly increased Gluma One Bond strength. No effect was observed for the other adhesives. The 10% NaOCl gel did not affect bond strengths. Ten percent NaOCl gel was less effective on collagen removal as compared to 10% NaOCl solution. The influence of collagen removal on bond strength is dependent on adhesive system, where both the solvent and the monomer can influence the results. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 72B: 339 –344, 2005 Keywords: collagen removal; adhesion; acetone-based adhesive system; ethanol-based ad- hesive system; shear bond strength; dentin bonding INTRODUCTION The integrity of the bond between dental substrates and adhesive materials has important implications in improving the success of composite resin restorations. 1 Increased adhe- sion between enamel and acrylic resin was initially observed by Buonocore, 2 who used 85% phosphoric acid on enamel prior to resin application. The subsequent development of a resinous matrix (BIS-GMA) 3 focused research on adhesion to enamel and dentin. The development of hydrophilic mono- mers 4,5 and the total etch technique 6 has resulted in reliable dentin bond strengths. Based in this technique, many proto- cols for dentin bonding require acid etching to remove the smear layer and partially demineralize the underlying den- tinal structures. Both peritubular and intertubular dentin are etched exposing the collagen-based organic matrix. When the dentinal tubules are exposed, in cross-section on the etched dentin surface, the etching pattern will result in funnel-shaped dentinal tubules. The so-called hybrid layer is formed when resin monomers are applied to this etched dentin, involving the exposed collagen fibrils and penetrating into the demin- eralized dentin. 4 Currently, researchers are investigating the durability and stability of the adhesive bond to dentin. 7,8,22 Wakabayashi and colleagues, 9 Sano and colleagues, 10 and Titley and col- leagues 11 reported that poor infiltration of the adhesive resin into the collagen-rich area of the demineralized dentin leaves gaps in the hybrid layer that, after long-term exposure to water, may be vulnerable to degradation. Some authors have questioned the quantitative contribution of the collagen lo- cated in the demineralized dentin to bond strengths. 1,12–14,17 Composite-to-dentin bond strengths after treatment of the dentin with sodium hypochlorite (NaOCl), a nonspecific pro- teolytic agent that removes exposed collagen fibrils in the demineralized zone, has been evaluated. 1,9,14 –23 Depending on the testing methodology and the adhesive system compo- sition, the application of sodium hypochlorite may increase, decrease, or have no effect on bond strengths. 18,20 For de- mineralized and deproteinized dentin, it has been suggested that acetone-based adhesives increase bond strengths com- pared to water- and ethanol-based adhesive systems. 14,18,24 To deliver an uniform and controlled application of NaOCl, its use as a gel has been studied. Perdigao and Correspondence to: L. A. Pimenta (e-mail: lpimenta@fop.unicamp.br) Contract grant sponsor: National Council for Scientific and Technological Devel- opment, Brazil; Contract grant number: 300924/1997-6; 475667/01 © 2004 Wiley Periodicals, Inc. 339