Microtensile bond strength of etch-and-rinse and self-etch adhesives to artificially created carious dentin Maria Carolina Guilherme Erhardt, DDS, MS, PhD n Maristela Maia Lobo, DDS, MS, PhD n Marcelo Goulart, DDS Fabio Herrmann Coelho-de-Souza, DDS, MS, PhD n Thiago Assuncao Valentino, DDS, MS, PhD n Jatyr Pisani-Proenca, DDS, MS, PhD Ewerton Nocchi Conceicao, DDS, MS, PhD n Luiz Andre Freire Pimenta, DDS, MS, PhD This article evaluates a pH-cycling model for simulation of caries- affected and caries-infected dentin (CAD and CID, respectively) surfaces, by comparing the bond strength of an etch-and-rinse and a self-etch adhesive system. For both adhesives, bonding to sound dentin (SD) showed that the microtensile bond strength (μTBS) values of SD, CAD, and CID were SD > CAD > CID ( P < 0.05). Knoop microhardness number mean values followed the same trend. Adhesive systems were not able to totally penetrate into CAD and CID, forming more irregular resin-dentin interdiffusion zones and atypical resin tags than SD. The tested in vitro pH-cycling caries model allowed the evaluation of specific dentin substrate alterations in response to μTBS. The type of dentin and its histological structure played an important role in etch-and-rinse and self-etch bonding, as lower μTBS values were attained in CAD and CID. Received: May 28, 2012 Accepted: November 26, 2012 C arious dentin consists of a soft, outer layer of caries-infected dentin (CID), in which caries is actively in progress, and a relatively harder inner layer of intact, bacteria-free remineraliz- able caries-affected dentin (CAD). 1,2 In light of the minimally invasive strategy for remineralization and dentin perme- ability reduction, the primary aim in the excavation of carious dentin is to remove only the outer layer of highly infected, denatured CID. 3,4 However, the inherent subjectivity in detection of the excavation boundary can result in clinically significant dif- ferences in the quality and quantity of dentin removed by different operators. 5 In operative treatment of carious lesions in dentin, the surface left at the end of cavity preparation will play a significant role in the bonding of the adhesive restor- ative materials. 6,7 Since it is very difficult for clinicians to verify the real dentin condition before placing a restoration, it is possible that adhesive procedures are being erroneously executed to substrates that are composed of sound dentin (SD), CAD, and CID in different parts of the same cavity. 8 Despite significant enhancements in dentin bonding technology, a deeper knowledge of resin adhesion to the dif- ferent dentin substrates would be helpful in developing more reliable and clinically long-lasting restorations. Therefore, it would also be useful to simulate CAD and CID conditions in vitro for evaluating bond strengths, since it might create a standardized substrate, permit- ting better comparisons among materials and techniques. 9,10 This in vitro study aimed to evaluate the microtensile bond strength (μTBS) of an etch-and-rinse and a self-etching bond- ing agent to artificially created CAD and CID surfaces. Materials and methods Thirty-six bovine incisors had their buccal surfaces ground flat (180-600 grit) under running water to provide uniform dentin surfaces. Flattened teeth were ran- domly divided into 3 groups (n = 12). The teeth in Group 1 (SD) were immersed in artificial saliva at 37° C during the experimental period, the teeth in Group 2 were submitted to an artificial induc- tion of CAD surfaces with a pH-cycling regimen, and the teeth in Group 3 were submitted to an artificial induction of CID surfaces with a pH-cycling regimen. Both CAD and CID pH regimens were developed modifying the models used by Shinkai et al and Wefel et al in prelimi- nary pilot/experimental studies. 11,12 The experimental specimens (Groups 2 and 3) received 2 coats of an acid-resistant, fast- drying nail varnish and a layer of sticky wax, except for a 25 mm 2 window on the buccal dentin surface. CAD specimens were submitted to 8 demineralization/hyper-remineralization cycles at 37° C. Each cycle included a 3-hour immersion in a demineralizing solution (156.25 mL/tooth, pH = 4.5) fol- lowed by a 45-hour immersion in a hyper- remineralizing solution (78.125 mL/tooth, pH = 7) that contained 10 ppm of fluoride. The demineralizing solution was renewed prior to the beginning of the fifth cycle, and the hyper-remineralizing solution was renewed prior to the beginning of each new cycle. 11,12 CID specimens were submitted to 4 demineralization/remineralization cycles at 37° C. Each cycle included a 2-hour immersion in a demineralizing solution (156.25 mL/tooth, pH = 4.5) followed by a 22-hour immersion in a remineralizing solution (78.125 mL/tooth, pH = 7). Both solutions were renewed prior to the begin- ning of each new cycle. The compositions of the pH solutions are listed in Table 1. Teeth from each dentin substrate (SD, CAD, and CID) were rinsed and ran- domly re-assigned to 2 subgroups accord- ing to the adhesive system used (n = 6). Table 2 displays mode of application, components, and manufacturers of each adhesive system. A total-etch self-priming adhesive system, Single Bond (SB), and a self-etching adhesive, Clearfil SE Bond (SEB), were applied following manu- facturers’ instructions. Resin build-ups, each 6 mm in height, were constructed incrementally (2 mm) with a microhybrid Caries Detection and Prevention 56 May/June 2014 General Dentistry www.agd.org