In Vitro lTBS of One-Bottle Adhesive Systems: Sound Versus Artificially-Created Caries-Affected Dentin Maria Carolina G. Erhardt, 1 Jose ´ Augusto Rodrigues, 2 Thiago Assunc ¸a ˜ o Valentino, 1 Andre ´ Vicente Ritter, 3 Luiz Andre ´ Freire Pimenta 4 1 Fellow Research, Department of Restorative Dentistry, Piracicaba School of Dentistry, University of Campinas, Sa ˜ o Paulo, Brazil 2 Associate Professor, Department of Restorative Dentistry, University of Guarulhos, Sa ˜ o Paulo, Brazil 3 Associate Professor, Department of Operative Dentistry, School of Dentistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 4 Clinical Professor, Department of Dental Ecology, School of Dentistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina Received 21 November 2006; revised 30 July 2007; accepted 1 October 2007 Published online 27 December 2007 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/jbm.b.31004 Abstract: This in vitro study aimed to evaluate a pH-cycling model for simulation of caries- affected dentin (CAD) surfaces, by comparing the bond strength of etch-and-rinse adhesive systems on sound and artificially-created CAD. Dentin substrates with different mineral contents and morphological patterns were created by submitting buccal bovine dentin to the following treatments: (1) immersion in artificial saliva during the experimental period (sound dentin, SD), or (2) induction to a CAD condition by means of a dynamic pH-cycling model (8 cycles, demineralization for 3 h followed by mineralization for 45 h). The bond strength of Excite or Prime and Bond NT adhesive systems was assessed using the microtensile bond strength (lTBS) test. Dentin microhardness was determined by cross-sectional Knoop evaluations. Resin–dentin morphology after the treatments was examined by scanning electron microscopy. SD produced significantly higher lTBS than CAD for both adhesives evaluated, without differences between materials. CAD exhibited lower microhardness than SD. Morphological analysis showed marked distinctions between SD and CAD bonded interfaces. Under the conditions of this study, differences in morphological pattern and dentin mineral content may help to explain resin–dentin bond strengths. The proposed pH-cycling model may be a suitable method to simulate CAD surfaces for bonding evaluations. ' 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 86B: 181–187, 2008 Keywords: caries-affected dentin; etch-and-rinse; bond strength; microtensile; pH cycling INTRODUCTION The primary aim of dentin caries excavation is to eliminate the outer layer of highly infected, irreversibly demineralized and denatured biomass known as caries-infected dentin. 1–3 This enables the preservation of the inner layer of partially- preserved and remineralizable caries-affected dentin (CAD). 4,5 However, CAD presents structural and composi- tional variations which may compromise effective bonding of resin-based materials. 6 CAD contains tubules that are filled with acid-resistant whitlockite minerals 3,4 due to deminerali- zation–remineralization cycles. 5 The mineral casts that occupy the dentinal tubules can interfere with the infiltration of adhesive resins and prevent resin tag formation during bonding. 7 Conversely, the increased porosity of intertubular dentin in CAD permits deeper etching of this substrate. 2,3 Currently, researchers are investigating the durability and quality of the adhesive bonds to sound dentin (SD) sub- strates. However, clinicians often have to bond to abnormal dentin, including CAD and hypermineralized dentin. 3 Perdiga ˜o et al. 8 introduced an artificial mineralization method to simulate hypermineralization and standardize this type of clinical substrate for bond strength studies. However, although hypermineralized dentin usually contains sclerosis products inside the tubules, this substrate is different than CAD, because the latter is partially demineralized by bacte- rial metabolic products. 2,3 Therefore, it would be also Correspondence to: L. A. F. Pimenta (e-mail: pimental@dentistry.unc.edu) Contract grant sponsor: FAPESP (The State of Sa ˜o Paulo Research Foundation); Contract grant number: 00/14049-1 ' 2007 Wiley Periodicals, Inc. 181